| surname | title | authors | abstract |
|---|---|---|---|
| Abbassi | The role of thermal conduction in magnetised viscous-resistive ADAFs | S. Abbassi, J. ghanbari, M. ghasemnezhad | Hot accretion flows likely proceed under week collision conditions. As a result thermal conduction by ions has a considerable contribution in transfer of the realized heat in accretion mechanisms. We study a 2D advective accretion disk bathed in a poloidal magnetic field of central accretor in the presence of the thermal conduction. We find self-similar solutions for an axisymmetric, rotating steady viscose-resistive magnetized accretion flow. The dominant mechanism of energy dissipation is assumed to be the turbulence viscosity and magnetic diffusivity due to magnetic field of the central star. We show that the dynamical quantities of ADAF s are sensitive to the viscosity, advection and thermal conduction parameters. Increasing the viscosity parameter decreases the density of the flow. Decreasing the thermal conduction decreases the radial velocity and increases the density of the flow in the equatorial plane. |
| Alexander | Evidence for large-scale energetic outflows in z~2 radio-quiet AGNs | D M Alexander, A M Swinbank | Leading models of galaxy formation require large-scale outflows from AGN to regulate the growth of galaxies and their central black holes. Here we present Gemini NIFS Integral Field Unit observations of two z~2 ultra-luminous galaxies hosting radio-quiet AGN activity. The broad, high velocity, and extended [OIII] emission found in these AGNs are similar to those of z>2 radio galaxies and suggest that large-scale accretion-related outflows are present in these systems. However, while it is typically argued that radio jets drive accretion-related outflows in radio-loud AGNs, the lack of luminous radio emission in these two AGNs indicates that another catalyst must be responsible for driving the outflows in these systems. We discuss possible outflow mechanisms and the prevalence of energetic outflows in distant radio-quiet AGNs.
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| Algaba Marcos | High Faraday rotation in VLBA AGN cores: a quest for correlations between optical and radio core polarization | J. C. Algaba, D. C. Gabuzda, P. S. Smith | Although the continua of AGN are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear if radio and high frequency emission originate in the same region in the jet. Previous works have shown that, after correction for VLBA core Faraday rotation, most BL Lacs have aligned VLBA-core and optical polarization angles (Gabuzda et al 2006). However, this relation is not clear for quasars (Algaba et al 2008). We present results of our new 12+15+22+24+43 GHz VLBA, exploring the possibility that some or all quasars have high core Faraday rotations, which led to n*pi ambiguities in earlier analyses. Our preliminary results suggest that core Faraday rotations of the order of tens of thousands of rad/m2 are common for quasars on the scales probed by these observations. We also present a joint analysis of our VLBA and simultaneous optical polarization data, continuing our quest for radio—optical correlations. |
| Almohammad | physical and geometrical elements of the short period eclipsing binary star MM Herculis | abdalla almohammad |
Abstract all the observations were made photoelectrically in b and v system. The observation was made with 48-inch cussegrain reflector at age university observatory. B and v observation of the RS CVn majors were made on 26 nights at age university observatory in 1984 and 1985 Evern analyzed the data in this paper by using Woods approach and later on the light curves of the same years treated by the method of Wilson devinney I started processing the mentioned data in Fourier transform method. I will determine the physical and geometrical elements of the short period eclipsing binary star MM Herculis using the mentioned data which observed in university of age by s.evren New light. Elements were calculated and the light curve for both b and v filters of the system appears to change in each cycle for both b and v filters. |
| Angelakis | Monitoring the radio spectra of selected blazars in the Fermi-GST era . The Effelsberg 100-m telescope covering the cm band | E. Angelakis, L. Fuhrmann, J. A. Zensus, N. Marcghili, I. Nestoras, T. P. Krichbaum | The analysis of the SED variability at frequencies from radio to TeV is a powerful tool in the investigation of the dynamics, the physics and the structure evolution occurring at the most exotic flavor of active galaxies, the blazars. In particular, the presence of Fermi-GST is providing a unique opportunity for such studies delivering gamma -ray data of unprecedented quality. Here we introduce a monitoring program that runs at the Effelsberg 100-m telescope since January 2007, pivoting a broad multi-frequency collaboration of facilities that cover the band from radio to infrared. 61 selected blazars are observed monthly between 2.64 to 43 GHz. The calibration accuracy is less than a few percent as it is demonstrated with some preliminary examples. |
| Anton | none | none | none |
| Antonuccio-Delogu | Global self-regulation of AGN activity. | V. Antonuccio-Delogu | We show that the large-scale backflow originating within the
cocoon produced by an AGN relativistic jet can have provide both a mass inflow and a compression of the accretion disk. The generation and evolution of this backflow arises from a basic principle of Fluid Dynamics ("Crocco Circulation Theorem"). Our model is supported by a set of 15 simulations (2- and 3D), using an Adapative Mesh Refinement code (FLASH v. 2.5). We find that these backflows are significant on typical timescales 3.5-4.1*10^7 yrs, i.e. about half the median AGN duty cycle, and for M_BH > 2.2*10^8 M_sun they can contribute mass fluxes of the order of ~ 1-6 M_sun yr.^-1. The enchanced SN energy input in the accretion disk, resulting from backflow compression and enchanced star formation "switches off" the accretion flux and the jet. This self-regulation mechanism does not require an extra input of accreting gas from e.g. "wet" mergers (A.-D. & Silk, 2008, 2009; A.-D., Shabala, Kaviraj and Silk, 2009). |
| Arevalo | Studying the connection between AGN accretion disc and corona through variability | P. Arevalo | The optical emission in AGN originates thermally from the accretion disc, but the origin of the X-rays in these objects is less clear. As the accretion disc is too cool to produce X-rays, it has been suggested that they arise from Compton upscattering of optical/UV photons by hot electrons in a corona. The origin of this corona is unknown, but its connection to other structures in the AGN can be probed observationally by following their variability. In this talk I will report on the results of a three year long, intensive monitoring campaign in X-ray and optical/NIR bands, carried out for a sample of AGN to establish the connection between these central emitting regions.
|
| Asmus | Where do accretion disks around black holes end? | Daniel ASMUS, Wolfgang J. DUSCHL | Accretion disks around (supermassive) black holes act as "machines" which extract gravitational energy. In fact, the observed radiation allows to sample the physical conditions very close to the event horizon. For a test particle, the innermost stable circular orbit(ISCO) is located at 3rs for a non rotating hole (Schwarzschild metrics; less for a rotating black hole). This ISCO is usually identified with the inner edge of the accretion disk. For a known black hole mass, it allows, in principle, to determine the Kerr parameter. In "real life", however, we deal not with test particles but with a viscous flow, which introduces additional forces. Results are presented of an investigation of the location of the inner edge in a more realistic environment. They show that this assumption doesn’t hold anymore, when radial advection of energy is taken into account whith a careful treatment of the transonic nature of the flow. |
| Baldi | The infrared nuclei of 3C radio galaxies: Jets, thermal emission or scattered light? | R. D. Baldi, M. Chiaberge, A. Capetti, W. Sparks, F. D. Macchetto, S. A. Baum, D. J. Axon, C. P. O'Dea, A. C. Quillen, and G. K. Miley | We measured infrared nuclear luminosities of 100 3CR radio galaxies with z<0.3 from HST NICMOS 2 observations. We modeled and subtracted the infrared galaxy light to isolate and to estimate the nuclear emission. We separated the objects into FR~I and FR~II and into LEG (low-excitation galaxies), HEG
(high-excitation galaxies) and BLO (broad-lined objects) with optical spectra. We performed a multi-wavelength analysis of the nuclei of the sample. The correlations among infrared, optical, and radio nuclear luminosity for the FR~Is and LEGs support the non-thermal origin of these nuclei. All BLOs show an infrared nucleus and a large infrared excess with respect to LEG and FR~I of equal radio core luminosity, due to the emission from hot circumnuclear dust. In the HEG nuclei, substantially fainter than those of BLOs, a significant contribution from light reflected in a circumnuclear scattering region is needed to account for their multiwavelength properties. |
| Bauer | none | none | none |
| Begelman | TeV flares from Blazar Jets | Begelman | none |
| Beilicke | AGN observations with VERITAS | M.Beilicke | The VERITAS collaboration operates an array of four imaging atmospheric Cherenkov telescopes in southern Arizona; regular observations with all four telescopes started in 2007. Active galactic nuclei (AGN) are an important component of the observation program. During the first 1.5 years of observation new gamma-ray emitting blazars were discovered and a variety of known TeV sources were measured with high precision. In many cases the observations were performed within coordinated multi-wavelength campaigns. The results and interpretation of the observations will be presented. |
| Beilicke | HX-POL -- A Balloon-Borne Hard X-Ray Polarimeter | M.Beilicke, A.Garson, J.Martin, H.Krawczynski, Q.Li, P.Dowkontt, E.Wulf, J.Kurfess,E.Novikova, G.De Geronimo, M.G.Baring, A.K.Harding, J.Grindlay, J.S.Hong | We report on the design and estimated performance of a balloon-borne hard X-ray polarimeter called HX-POL. The experiment uses a combination of Si and Cadmium Zinc Telluride (CZT) detectors to measure the polarization of 50-500 keV X-rays from cosmic sources through the dependence of the angular distribution of Compton scattered photons on the polarization direction. On a one-day balloon flight, HX-POL would allow us to measure the polarization of bright Crab-like sources for polarization degrees down to 5%. On a longer (15-30 day) flight from Australia or Antarctica, HX-POL would be be able to measure the polarization of bright sources down to polarization degrees of 1%. Hard X-ray polarization measurements provide unique venues for the study of particle acceleration processes by compact objects and relativistic outflows. In this contribution, we discuss the overall instrument design and performance. Furthermore, we present results from laboratory tests of the Si and CZT detectors. |
| Belfiore | none | none | none |
| Benitez | Spectroscopic monitoring of the Blazar 3C454.3 | E. Benitez, V. Chavushyan, D. Dultzin, O. Martinez, B. Perez-Camargo & J. Torrealba | I will present the main results on the spectroscopic monitoring done to the Blazar 3C 454.3 (z=0.859) from September 2003 to July 2008. A total of 16 optical spectra were obtained
in different runs. The spectra clearly show the different activity stages underwent by this object. The spectroscopic analysis reveals an overall variation of the Mg II ($lambda$ 2800 AA) broad line component flux by a factor of $sim$3, while the corresponding UV continuum (F$_{Cont}$ at $lambda$ 3000 AA) flux has changed by a factor of $sim$14. The broad component of the Mg {small II} emission lines respond proportionally to the changes in the continuum when the source is in a low-activity state. However, during the optical outbursts detected in 2005 and 2007, the Mg {small II} emission lines behave in a different way showing no or little response to the continuum flux variations. |
| Bianchin | Monitoring the high-z Flat Spectrum Radio Quasar PKS 2149-306: recent observations with INTEGRAL and Swift | Bianchin V. et al. | We present preliminary results of the multiwavelength campaign on
the high-z (z=2.345) FSRQ PKS 2149-306. The source has been recently observed by INTEGRAL (April-May 2009) and simultaneous pointings were activated with Swift (XRT and UVOT). We discuss the broad-band spectral properties, comparing present results with archival data. |
| Bonning | Correlated variability in the blazar 3C 454.3 | E. Bonning, C. Bailyn, C. M. Urry, M. Buxton, G. Fossati, L. Maraschi, P. Coppi, R. Scalzo, J. Isler, A. Kaptur | The blazar 3C 454.3 was revealed by Fermi Space Telescope to be in an exceptionally high flux state in July 2008. We performed a multi-wavelength monitoring campaign from August through December 2008 on this blazar using IR and optical observations from the SMARTS telescopes together with publicly available data from Swift and daily gamma-ray fluxes from Fermi. We find an excellent correlation between the IR, optical, UV and gamma-ray light curves,
with a time lag of less than one day. The amplitude of the infrared variability is comparable to that in gamma-rays, and larger than at optical or UV wavelengths. The X-ray flux is not strongly correlated with either the gamma-rays or longer wavelength data. We will discuss these variability characteristics as well as the varying spectral energy distribution (SED) in the context of the external Compton model. Other recent notable observations of flaring blazars from the Yale/SMARTS monitoring program will also be discussed. |
| Boutelier | An inhomogeneous jet model for VHE emission from blazars: | Boutelier, T., Henri, G., Petrucci, P.-0. | We present a new time-dependent inhomogeneous jet model of blazar emission. Ultra relativistic leptons are injected at the base of a jet. The particle EDF evolution (heating, cooling, pair production) and the SSC jet emissivity are computed as the particles propagate along the jet. Time-dependent jet emission is computed by varying the particle injection, but due to the sensitivity of pair production process, only small variations in the injection are required during flares. The stratification of the jet emission, together with a pile-up distribution of particles, allow significantly lower bulk Lorentz factors, compared to one-zone models, and a large variety of multiwavelength behaviours. We apply the model with success to the big flare of PKS 2155-304 observed in 2006. We reproduce its average broad band spectrum from radio to TeV, the spectral variability of the TeV spectrum and the light curves in optical, X-ray and TeV during the flare, with bulk Lorentz factor lower than 15.
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| Boutelier | The influence of collimation on the appearence of relativistic jets | Boutelier, T., Henri, G., Petrucci, P.-0. | The question of the collimation of relativistic jets is the subject of a lively debate in the communauty.
We numerically compute the apparent velocity and the Doppler factor of a non homokinetic jet using different velocity profile, to study the effect of collimation on the appearence of relativistic jets (apparent velocity and Doppler factor). We argue that if the motion is relativistic, the high superluminal velocity are possible only if the geometrical collimation is smaller than the relativistic beaming angle gam$^{-1}$. In the opposite case, the apparent image will be dominated by the part of the jet travelling directly towards the observer resulting in no apparent velocity. Furthermore, getting rid of the homokinetic hypothesis yields a complex relation between the observing angle and the Doppler factor, resulting in important consequences for the numerical computation of AGN population and unification scheme model. |
| Braito | Gaining new insight on the absorbing matter in Seyfert2 Galaxies | V. Braito, J.N. Reeves, R. Della Ceca, G. Risaliti | X-ray observations of Seyfert 2 have shown that the distribution
and ionization state of the circumnuclear absorbing material is more complex than the simple homogeneous torus predicted by the Unification Scheme of AGN. To investigate the nature of this material broad bandpass is required to constrain the X-ray continuum and measure the Compton reflection hump. On the other end both high sensitivity and energy resolution are needed to detect relatively faint emission and absorption features, which could arise from the distant hot scattering region or from outflowing matter. We present the first results of a sample of the local brightest Compton Thin Sey2 observed with Suzaku. Suzaku's high sensitivity and bandpass allowed us to better constrain the primary X-ray continuum and investigate the nature of the reprocessing matter. |
| Branduardi-Raymont | none | none | none |
| Browne | A dichotomy in jet orientations in elliptical galaxies | I.W.A. Browne & R.A. Battye | We have examined the position angle differences of the optical and radio emission of 14302 SDSS galaxies identified with extended FIRST radio sources. We separate elliptical galaxies for star-forming and other galaxies by a combination of colour and concentration. In the ellipticals there is a statistically highly significant trend for the radio emission to be aligned with the optical minor axes, something which expected for oblate spheroidal galaxies with jets emerging along their minor axes. Remarkably this trend is confined to the radio quieter portion of the elliptical population. We suggest that this dichotomy in nuclear alignment properties relates to whether or not the galaxy is rotationally supported or not. There are implications for the accretion efficiencies in the different types of galaxy. |
| Bruschini | none | none | none |
| Buttiglione | Optical spectroscopy of 3CR sources: accretion and jet launching in radio galaxies | Sara Buttiglione, Alessandro Capetti, Annalisa Celotti | We use a 92% complete optical spectra dataset of 100 3CR radio sources with z<0.3 to explore their spectroscopic and multiwavelength properties. We find the presence of two main sub-populations, High and Low Excitation Galaxies. All broad-line objects are HEG from the point of view of their narrow emission line ratios and all HEG are associated to FRII radio-galaxies. Conversely LEG are of both FRI and FRII type. In a line vs radio luminosity plane, HEG and LEG obey to two linear correlations, with HEG being 10 times brighter than LEG in [OIII]. HEG and LEG are also separated in a plane that compares black hole mass and nuclear luminosity. The transition from LEG to HEG occurs at a ~0.001 fraction of the Eddington luminosity. LEG show a lower level of accretion, of line and nuclear luminosities, but they
can be associated to the most powerful FRII radio-sources of the sample. This suggests that the processes of accretion and the jet launching are at least partially decoupled. |
| Caccianiga | The XBS sample of type1 AGN: Radio-loudness vs. physical parameters | Caccianiga, A., Severgnini, P., Della Ceca, R., Corral, A., Marchese, E. | The origin of the differences between radio-loud (RL) and radio-quiet (RQ) AGN is an important matter of debate. The possibility that the radio-loudness is related to some physical parameters, like the black-hole mass or the accretion rate, has been widely discussed in the literature. Here we present a comparison between RL and RQ AGN selected in a statistically
complete X-ray survey, the XMM-Newton Bright Survey (XBS), which has now a high identification rate (~92%). In particular, we have estimated the black-hole masses and accretion rates for the ~240 type1 AGN included in the survey and we have looked for systematic differences between objects classified as radio-loud and radio-quiet. We summarize here our main conclusions. |
| Calcidese | none | none | none |
| Cao | An accretion disc-corona model for X-ray spectra of active galactic nuclei | Xinwu Cao | The hard X-ray spectral index is found to be correlated with L_bol/L_Edd, and L_bol/L_x increases with L_bol/L_Edd. The Compton reflection is found to be correlated with the hard X-ray spectral index. We construct an accretion disc-corona model and calculate the spectra with different magnetic stress tensors, in which the corona is assumed to be heated by the reconnection of the magnetic fields generated by cold disc. Our calculations show that both alpha p_gas and alpha p_tot fail to explain all these observational features. The resulted spectra with alpha (p_gas p_tot)^1/2 show that both the hard X-ray spectral index and L_bol/L_x increase with L_bol/L_Edd, which are consistent with the observations. The disc-corona model is unable to reproduce the observed very hard X-ray continuum emission from the sources accreting at low rates. We suggest that the disc-corona system transiting to an ADAF+disc corona system at low accretion rates may be able to explain all these correlations. |
| Capetti | none | none | none |
| Celotti | |||
| Chajet | AGN Accretion Disk Winds and Emission-Line Blueshifts | Laura S. Chajet*, Patrick B. Hall*, * York University | Observations show that for most quasars the broad emission lines are single-peaked and considerably blueshifted. The Murray & Chiang (1997, MC97) accretion disk-wind model accounts for these features, although the amount of blueshifting is small compared with observational results. Here we present preliminary results of our extension of the MC97 model to the case of non-negligible radial and vertical velocities. The goal is to search for combinations of parameters where the modified model not only reproduces the single-peaked characteristic of the broad emission lines as the original model did, but also renders blueshifts more consistent with observations.
As a first step towards a whole extension of the model to include magnetohydrodynamic effects, we also combine the extended wind model with the restricted class of self-similar solutions of the ideal MHD equations given by Emmering, Blandford & Shlosman (1992). |
| Chang | A closer look to the flaring feature in the M 87 jet | C. S. Chang, E. Ros, Y. Y. Kovalev, M. L. Lister | The radio-loud active galactic nucleus M 87 hosts a powerful jet fueled by a super-massive black hole in its center. A bright feature 80pc away from the M87 core, labeled as HST-1, has been reported to show blazar-like activity during the last years. Earlier radio, optical and X-ray observations have shown that HST-1 is superluminal, and is possibly connected with the NUV, X-Ray, and TeV flare observed around 2005. To examine the possible blazar-like nature of HST-1, we analyzed 2cm VLBA data observed from 2000 to 2008. HST-1 is successfully detected at VLBI 2cm with milliarcsecond resolutions from 2003 to 2007. We present high-resolution images of this feature, and discuss the connection between our radio results and high energy emission. |
| Colpi | BINARY BLACK HOLES IN GASEOUS CIRCUM-NUCLEAR DISCS: LINKING SPIN AND ACCRETION TO DYNAMICS |
M. Colpi | During a major merger,the black holes nested inside their own bulges sink under the action of dynamical friction and pair. As the merger reaches completion, the black holes end forming a Keplerian binary which continues to harden transferring angular momentum to gas that is present in the form of a massive circum-nuclear. We here report on N-body/hydrodynamical simulations designed to follow the dynamics of black holes in circum-nuclear discs that show the existence of a close relationship between the mass accretion rate and the hole's dynamics. Accretion can be highly variable, depending on the degree of eccentricity of the black hole orbit, and on whether the orbit is co- or counter-rotating relative to the disc. Spin evolution is traced self-consistently. The acting torques suffice to align the orbit and the spin of the black holes with the large scale flow, leading to black hole coalescence at the center of the remnant galaxy with low recoil velocity. |
| Covino | none | none | none |
| Dallacasa | Young Radio Sources | Daniele Dallacasa & Monica Orienti | Young radio sources are small objects in which the radio plasma interacts with the densest and innermost region of the AGN. Some diagnostics of the ambient medium can be derived from the properties of the pc-scale radio emission. A brief summary of the characteristics (size, age, polarization, growth speed, etc.) of small radio sources will be given together with the consequences on the properties of the ambient medium (density, ionization, inhomogeneities, etc), by discussing a few examples. |
| D'Ammando | Not only once: the amazing gamma-ray activity of the blazar PKS 1510-089 | Filippo D'Ammando on behalf of the AGILE Team | PKS 1510-089 is a powerful Flat Spectrum Radio Quasar at z=0.361 with radiative output dominated by the gamma-ray emission. In the last two years PKS 1510-089 showed high variability over all the electromagnetic spectrum and in particular very high gamma-ray activity was detected by the Gamma-Ray Imaging Detector on board the AGILE satellite with a flaring episode in August 2007, March 2008 and an extraordinary activity in March 2009 with several flaring episodes and a flux that reached 5x10^-6 ph cm^-2 s^-1. Multiwavelength observation of PKS 1510-089 seems to indicate the presence of Seyfert-like features such as little blue bump and big blue bump. Moreover X-ray observations suggested the presence of a soft X-ray excess that could be a feature of the bulk Comptonization mechanism. We present the results of the analysis of the multiwavelength data collected by GASP-WEBT, REM, Swift and AGILE during these gamma-ray flares and the theoretical implication for the emission mechanisms. |
| Decarli | none | none | none |
| Della Ceca | none | none | none |
| del Olmo | AGNs and Environment: The AGN Population in Compact Groups. | A. del Olmo, J. Perea & M.A. Martinez Carballo | We present a clear relation between the type of nuclear activity in galaxies and their environment. We carried out a survey to determine the frequency and nature of the activity in 2 Compact Group samples: the Hickson one(HCGs) and the Updated Zwicky Catalog of CGs. We obtained new spectra for 200 galaxies in 64 HCGs, and 70 from the literature. We also collected spectra for 720 galaxies in 215 UZC-CGs from SDSS, FAST and Z-Machine archives. We found a extremely low ratio of Broad to Narrow Line AGNs, 3-6% in CGs compared to 22-43% in other environments. Also notably low is the Sy1/Sy2 ratio, 8-19% in CGs vs. 61%. This appears as a real deficiency of BLAGNs, since there is no such deficit of AGNs in CGs, at least 65% of the emission galaxies
host an AGN. Such deficiency could be related to the CG environment, where galaxies suffer slow encounters and morphological transformations that result in an important decrease of the gas that can reach the nucleus to form the BLR. |
| Donnarumma | The June 2008 flare of Markarian 421 from optical to TeV energies | I. Donnarumma, J. Grube, M. C.Raiteri, S. Vercellone, M. Villata, R.M.Wagner, for the AGILE and GASP-WEBT teams and the MAGIC and VERITAS collaborations | We present optical,X-ray,high-energy (HE) and very-high energy gamma-ray observations of the HBL blazar Mrk 421 taken between May 24-June 23 2008.A HE gamma-ray signal was detected by AGILE-GRID in June 9-15,brighter than the EGRET average flux by a factor of 1.5.In hard X-rays (20-60 keV),SuperAGILE resolved a 5-day flare with a maximum flux of~55mCrab.SuperAGILE,RXTE/ASM and Swift/BAT data show a correlated flaring structure between soft and hard X-rays.Hints of the same flaring behavior is also detected in the simultaneous optical data.Swift/XRT revealed on June 12-13 the highest 2-10 keV flux ever observed (>100mCrab).Observations at VHE (E>200GeV) gamma-rays with MAGIC and VERITAS in the period June 6-8 show the source flux peaking in a bright state, well correlated with the simultaneous peak in the X-rays.We argue that the gamma-ray flare can be interpreted within the framework of the SSC model in terms of a rapid acceleration of leptons in the jet. |
| Evans | The Chandra HETG and Suzaku View of the NLR and Radio-Loud/Radio-Quiet Dichotomy in AGN | Daniel Evans, Julia Lee, James Reeves, Herman Marshall, Claude Canizares | We use high-resolution X-ray gratings spectroscopy, together with broadband X-ray spectra to probe the nuclei and circumnuclear environments of AGN and elucidate the connections between accretion and outflows:
First, we present the only spatially resolved high-resolution X-ray spectra of the nucleus and NLR in an AGN, using a new 400-ks Chandra HETG observation of NGC 1068. We use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature along the NLR, and argue that AGN photoionization dominates its energetics, rather than jet collisional ionization. Next, we show new evidence from Suzaku for systematic differences in the X-ray spectra of radio-loud and radio-quiet AGN. We find RL AGN systematically lack the relativistic Fe Ka lines and strong Compton reflection that we observe in RQ AGN. We examine our results in the context of models that argue jet production is governed by the ionization state of the accretion flow and BH spin. |
| Fanidakis | AGN in hierarchical galaxy formation models | Nikolaos Fanidakis, Carlos Frenk, Shaun Cole, Chris Done, Carlton Baugh, Richard Bower | We present a new theoretical model of the evolution of the mass and spin of SMBHs. The calculation is embedded in the GALFORM semi-analytical model, which follows the formation and evolution of galaxies in a CDM universe. The BH and galaxy formation models are fully coupled: the semi-analytic model computes the rate at which gas is added to the BH, while the emission from the BH regulates the gas cooling. We track the evolution of BH spin through BH mergers and gas accretion. We find that the overall distribution of spins is bimodal when the accretion of gas occurs via a self-gravity limited disk. With our predictions for the mass, spin and accretion rates of the BH, and by assuming the Blandford-Znajek mechanism for jet production, we can predict the optical and radio emission from AGN. The model reproduces remarkably well the radio properties of AGN. This is the first confirmation that AGN-feedback in galaxy formation models reproduces the observed properties of AGN.
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| Fernández Ontiveros | The intriguing nucleus of NGC 253 at parsec scales from radio to X-rays | J.A. Fernández-Ontiveros, M.A. Prieto, J.A. Acosta-Pulido, O. Gómez-MartÃn, M. Orienti | NGC 253 is one of the nearest starbursts and hosts a strong radio source which has been proposed as a low-luminosity AGN. We performed observations with VLT/NaCo adaptive optics in the near-infrared and VLT/VISIR in the mid-infrared, completing this set with data in the optical (HST), radio (VLA) and X-rays (Chandra).
A new alignment at parsec scales is found for NGC 253 between NIR and radio data. A surprising fact is the lack of any optical or IR counterpart for the assumed radio nucleus, which presents an IR-to-radio emission ratio similar or lower than SgrA*, questioning this source as the origin of the nuclear activity. In contrast, a deeply embedded X-ray source is detected in the centre, suggesting that this object could be one of the best examples of the beginning or ending of an active nucleus. The new alignment permits us to investigate the nature of this source from radio wavelengths to X-rays, connecting it with the starburst component. |
| Ferreira | Jet Emitting Discs: a new accretion flow solution | Ferreira, J, Petrucci, P.-O., Henri, G., Pelletier, G., Foellmi, C., Murphy, G. | We present a model where the innermost regions of accretion discs around AGN are pervaded by a large scale magnetic field of bipolar topology. It will be shown that once this field becomes large enough, a new class of accretion flow sets in where most of the released accretion power feeds two self-collimated jets.
Such a Jet Emitting Disc has dynamical properties quite different from both the standard and advection dominated discs. It also exhibits three different thermal equilibrium branches at a given radius: two stable (cold and hot) and one intermediate unstable. The hot solution has been for instance successfully applied to the Low/Hard states of microquasars. Within this approach, a global understanding of accretion modes around compact objects requires to reinvestigate the issue of field advection in turbulent, magnetized disks. |
| Filho | Powerful Radio Galaxies with no Optical Counterpart | Filho, Brinchmann, Lobo, Anton | In our inspection of SDSS galaxy clusters, we have found several powerful radio galaxies in the FIRST survey which do not have optical counterparts. We have followed this up with deep HAWKI K- band observations of the field. We here present the results and analysis of the HAWKI observations. |
| Foschini | BLAZAR VARIABILITY AT GAMMA-RAYS AS OBSERVED BY FERMI/LAT | S. Ciprini, E.C. Ferrara, L. Foschini, B. Lott, G.M. Madejski, E. Massaro, M. Pepe, G. Tosti on behalf of The Fermi/LAT Collaboration | It is known that blazars display strong and erratic variability at any wavelength. However, studies at gamma-rays are often hampered by instruments limits. The advent of Fermi/LAT makes it possible to explore - for the first time at gamma-rays in the 0.1-100 GeV band - the time evolution of several of these sources with high-time resolution (the brightest ones). Here we present preliminary results of a study of the global time properties of a sample of blazars detected by Fermi/LAT during the first six months of operations. Particular emphasis is given to the brightest sources, for which we can measure flux and spectral changes on daily timescales. |
| Foschini | Fermi/LAT discovery of gamma-ray emission from a relativistic jet in the Narrow-Line Quasar PMN J0948+0022 | L. Foschini on behalf of the Fermi/LAT Collaboration, G. Ghisellini, L. Maraschi, F. Tavecchio, E. Angelakis | We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope of high-energy gamma-ray emission from the peculiar quasar PMN J0948+0022 (z=0.584602). Contrary to the expectations, the optical spectrum of this quasar shows only narrow lines [FWHM(H_beta)~1500 km/s] and the typical characteristics of narrow-line Seyfert 1 type galaxies. However, the strong radio emission and flat spectrum suggest the presence of a relativistic jet, which can be now confirmed with the detection of MeV-GeV photons. PMN J0948+0022 is therefore the first radio-loud narrow-line Seyfert 1 quasar to be detected in gamma-rays. |
| Fossati | Blazar Demographics and Sequence with Fermi | Giovanni Fossati, Eileen Meyer | Over the last several years we have seen limited progress in our
understanding of radio-loud AGNs. Among the questions still open are those about their demographics and understanding of their broad phenomenology. While disputed, the general concept of the blazar sequence has remained the leading "general" framework for organizing and hopefully understanding the properties of blazars. We will report on our work based on the FIRST Flat Spectrum Sample (FFSS), a new kind of deep radio sample, unbiased with respect to X-ray emission, designed to capture the widest possible range of phenomenology at once. The FFSS comprises about 600 objects representing a very diverse mix of FSRQ, BL Lacs, "galaxies", and SED colors. The FFSS work is accompanied by the study of gamma-ray selected AGN from the Fermi all sky survey. In particular we will focus on our the progress towards the immediate goal of testing the current luminosity/SED-color sequence paradigm, and on the relevance of/for Fermi. |
| Fuhrmann | Fermi/LAT and multi-wavelength observations of quasar 3C 454.3 during the2008 outburst | L. Fuhrmann on behalf of the of the Fermi/LAT collaboration plus external collaborators | 3C 454.3 is an highly active quasar repeatedly showing strong outbursts over the last years. In its early phase of operation, the Fermi/LAT instrument detected highly variable gamma-ray emission from the source with a strong outburst in July 2008. Consequently, the LAT team organized a large multi-wavelength campaign including radio cm/mm/sub-mm, IR, optical, UV and X-ray observations. We here report first detailed results of this campaign (July 2008 - January 2009) comparing the Fermi/LAT gamma-ray behavior of 3C 454.3 with its simultaneous, highly variable multi-wavelength behavior and discuss its physical implications. |
| Fukumura | X-ray Absorption of MHD Wind from Accretion Disks | K. Fukumura, D. Kazanas, & E. Behar | We consider an X-ray absorbing MHD wind originating from an accretion disk to which global poloidal magnetic fields are anchored. Wind properties (e.g. column density, velocity fields) are self-similarly obtained by solving MHD (Bernoulli) equations, while photoionization and atomic physics are computed under thermal equilibrium by utilizing XSTAR code. For a given line-of-sight (LOS) angle through wind materials model spectra are obtained to show distinct absorption signatures. Interesting wind properties such as ionic column densities and wind temperature, our model explains well a constant column density of gas over LOS with varying ionization state in absorption measure distribution as implied by some observations of bright quasars (e.g. IRAS13349+2438) and AGNs (e.g. NGC3783). |
| Furniss | Multiwavelength Observations of Intermediate Peaked BL Lac Objects Detected by VERITAS | Amy Furniss for the VERITAS Collaboration | We report on the discovery of very high energy emission (E > 200 GeV) from the intermediate peaked BL Lac (IBL) objects of W Comae and 3C66A by VERITAS. These IBL objects bridge the gap between low energy peaked and high energy peaked BL Lacs and are the first of their kind to be detected in this energy band. We present results on the energy spectra measured by VERITAS for these two AGN. Observation of these objects in flaring states prompted quasi-simultaneous observations in other wavebands. This MWL data allows the fitting of models to the double peaked SED, in order to test how well the models describe the data and determine characteristics of the particle populations emitting these very high energy photons. |
| Gaskell | Inflow of the Broad Line Region and Torus | C. Martin Gaskell & Rene W. Goosmann | We show how velocity-resolved reverberation mapping, the blueshifting of high-ionization lines, and the spectropolarimetry all imply that the broad-line region (BLR) has a net inflow in addition to the dominant rotational and turbulent motions. We have proposed (Gaskell & Goosmann 2008, arXiv:0805.4258) that the previous apparent conflict between the net inflow implied by reverberation mapping (Gaskell 1988, ApJ, 325, 114; Koratkar & Gaskell 1989, ApJ, 345, 637) and the relative blueshifting of the high-ionization BLR lines (Gaskell 1982, ApJ, 263, 79) is resolved by scattering off infalling material. Spectropolarimetry provides addition support for this picture (Smith et al. 2005, MNRAS, 359, 846). The BLR mass influx is sufficient to power the AGN. We argue that the high blueshiftings of the UV lines in Narrow-Line Seyfert 1s are due to enhanced BLR inflow rates rather than strong winds. We suggest that a significant part of the narrow line region (NLR) is also inflowing. |
| Georganopoulos | How much light was produced since the Universe was born? Finally, a way to measure it. |
Markos Georganopoulos | The extragalactic background light (EBL) that permeates the Universe in
the optical-IR is essentially an integral of the light produced from the time the first stars were formed in our Universe until now. As such, it is a quantity that is very closely connected to the galaxy/ large scale structure formation in our Universe. Unfortunately, measuring the EBL has been proven very difficult, for very simple reasons that I will discuss in the first part of my talk. Luckily, we found a parameter-free way to break the deadlock of measuring the EBL with Fermi, NASA's new Gamma-ray satellite, observations of the lobes of the nearby radio galaxy Fornax A. This will be the second part of my talk. Fermi measurements are underway. |
| Ghirlanda | none | none | none |
| Ghisellini | The Fermi blazars divide | Ghisellini G., Maraschi L., Tavecchio F. | Bright Flat Spectrum Radio Quasars (FSRQs) and BL Lacs detected by Fermi neatly separate in the gamma-ray spectral index vs gamma-ray luminosity plane. BL Lacs are less luminous and have harder spectra than FSRQs. We show that the divide between the two subclasses of blazars corresponds to an accretion rate ~0.01 the Eddington one, at the transition between optically thick and radiatively inefficient accretion flows. The separation in hard (BL Lacs) and soft (FSRQs) objects then results from the different radiative cooling of the relativistic electrons in jets propagating in different ambients. Most luminous blazars already detected by Fermi should have large black hole masses, around 1e9Mo. Lowering the gamma-ray flux threshold the region of the alpha_gamma-L_gamma plane corresponding to steep spectra and lower L_gamma will be populated by FSRQs with lower mass black holes, while the region of hard spectra and large luminosities will remain forbidden. |
| Gianni' | X-ray overview of blazars observed by INTEGRAL | S. Gianni', A. De Rosa, A. Bazzano, P. Ubertini, L. Bassani on behalf of the INTEGRAL/AGN survey team | We present a broadband (0.2-200keV) X-ray study of a sample of blazars observed with INTEGRAL, Swift and XMM-Newton. Our aim is to investigate several open questions about the emission processes of these objects, the nature of their environment and its interaction with the jet. In particular, we analyse the physical interpretation of the flattening or/and steepening in the spectrum shape in the soft X-rays energy band. All but one (4C04.42) sources show a spectral flattening below 3 keV (observer frame) that can be interpreted as due either to intrinsic cold absorption, as already suggested in literature, or to a curvature of the intrinsic continuum. The blazar 4C04.42 shows instead a low-energies spectral steepening that can be interpreted as a signature of a bulk Compton of 'cold' relativistic electrons in the jet interacting with photon field originated outside the jet. The distribution of spectral parameters (absorbing column density, spectral index, redshift) is also studied. |
| Giroletti | Radio emission from Fermi AGNs and its relation to the gamma-ray properties | M. Giroletti on behalf of the Fermi/LAT Collaboration | Radio and gamma-ray emission from AGNs are thought to share a common origin, related to the ejection phenomena in the vicinity of super massive black holes (relativistic jets). Indeed, the vast majority of the high galactic latitude, non-pulsar sources discovered by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope are associated with radio sources, in agreement with the previous findings of the 3EG catalog. Capitalizing on the data provided by the LAT (flux, spectral index, variability) and on the associations found in CRATES, BZCAT, and the literature, we will report on the radio properties of the LAT detected AGNs, and their possible connection to the gamma-ray data.
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| Giustini | VARIABLE X-RAY ABSORPTION IN mini-BALQSOs | Margherita Giustini, Massimo Cappi, George Chartas, Michael Eracleous, Giorgio G.C. Palumbo, Cristian Vignali | We present results from a temporally resolved X-ray spectral analysis performed on three miniBAL quasars,namely PG1535+547 (z=0.04),PG1126-041 (z=0.06) and PG1351+640 (z=0.09).
The first two sources exhibit similar timing characteristics,showing strong spectral variability on timescales of hours,days,and years.Their complex behavior can be reproduced by variations of physical parameters of an ionized gas absorbing the primary continuum.The shortest timescale spectral variations can be best reproduced by the variations of the covering fraction of an inner ionized absorber,while the longest timescale variations are better reproduced by column density and/or ionization parameter variations of an outer ionized absorber.The latter source exhibits dramatic spectral variations on years timescales,which are ascribed to strong column density variations along the line of sight. We discuss the implications of our observational results for theoretical models of outflows in radio-quiet quasars. |
| Gliozzi | PKS 0558Â-504: an ideal laboratory to study the accretion-ejection link | Mario Gliozzi (GMU), Iossif Papadakis (University of Crete), Lucyna Kedziora-Chudczer (University of Sydney), Dirk Grupe (PSU) | The radio-loud Narrow-Line Seyfert 1 galaxy PKS 0558Â-504 is a
highly variable, X-ray bright source with super-Eddington accretion rate and a powerful radio jet, and hence represents an ideal laboratory to study the link between accretion and ejection phenomena. Here we present the preliminary results from an ongoing multi-wavelength monitoring campaign that covers the radio band with the ATCA and VLBI, the optical, UV and soft X-rays with Swift, and the hard X-rays with RXTE. We combine complementary pieces of information from different energy bands to shed some light on the energetics of accretion and ejection phenomena in this system and on the interplay between the 3 fundamental ingredients in black hole systems: disk, corona, and jet. |
| Gomez | Stratification in polarization and Faraday rotation in the jet of 3C120 | Gomez, Agudo, Roca-Sogorb, Marscher, Jorstad | We present a sequence of 12 monthly polarimetric 15, 22, and 43 GHz VLBA observations of the radio galaxy 3C120 revealing a systematic presence of gradients in Faraday rotation and degree of polarization across and along the jet. We find a localized region of high Faraday rotation measure superposed on this structure between approximately 3 and 4 mas from the core, with a peak of 6000 rad/m2. Interaction of the jet with the external medium or a cloud would explain the confined region of enhanced Faraday rotation, as well as the stratification in degree of polarization and the flaring of superluminal knots when crossing this region. The data are also consistent with a helical field in a two-fluid jet model, consisting of an inner, emitting jet and a sheath containing nonrelativistic electrons. The polarization electric vectors require a dominant component parallel to the jet axis (in the frame of the emitting plasma) for the magnetic field in the emitting region. |
| Grandi | Radio to X-ray study of a sample of 3CRR sources | Grandi, P., Bianchin V., Cavazzuti, E., Malaguti, G., Maraschi L.,
Massaro, F |
We present a study of 93 3CRR radio sources, for which both 5GHz core flux and at least one X-ray observation are available. The sample includes 18 FRI and 75 FRII optically classified as High Excitation Galaxies, Low Excitation Galaxies, Weak Quasars and Quasars. The X-ray (2-10 keV) and 5GHz luminosities span about seven and eight orders of magnitude, respectively. For each FR group (and optical FRII sub-class), several observables (radio-X-ray spectral index, mass accretion rate, jet kinetic
power, etc) are explored. We compare physical and geometrical properties in order to assess the jet contribution in the different classes and to characterize any possible jet-disk relationship. |
| Grupe | The Big-Blue-Bump in Soft X-ray Selected AGN oberved by Swift | Dirk Grupe, Karen Leighly, & Stefanie Komossa | We report on Swift observation of a sample of 90 bright soft X-ray selected
AGN. This sample is the largest number of AGN to study the spectral energy distribution of AGN ever performed with simultaneous Optical/UV and X-ray data. The main motivation of this study is to obtain simultaneous optical/UV and X-ray observations in order to study the Big-Blue-Bump emission in the spectral energy distributions of AGN and search for observed properties that can be used to estimate the Eddington ratio L/Ledd. We find strong correlations of the X-ray spectral slope and the Optical/UV slope with L/Ledd. We note an offset in the alph-uv - L/Ledd relation between Narrow-Line Seyfert 1s and Broad Line Seyfert 1s. One interpretation of this result is that NLS1s and BLS1s have different accretion disk properties. We find that although NLS1s have steeper X-ray spectral slopes and higher L/Ledd than BLS1s, their optical/UV to X-ray spectra slopes alpha-ox are very similar. |
| Gu | Flat-Spectrum Radio Quasars from SDSS DR3 Quasar Catalogue | Minfeng Gu | We constructed a sample of 185 Flat Spectrum Radio Quasars
(FSRQs) by cross-correlating the Shen et al.'s SDSS DR3 X-ray quasar sample with FIRST and GB6 radio catalogues. For the subsample of 118 nonthermal jet-dominated FSRQs, we found 25 FSRQs having higher synchrotron peak frequency > 10^15 Hz than the typical value for FSRQs. The weak anti-correlation is found between the synchrotron peak frequency and peak luminosity, however it becomes significant when combining with the Wu et al.'s sample of 170 BL Lac objects. We found significant correlations between the peak luminosity and black hole mass, the Eddington ratio, and the BLR luminosity, indicating that the jet physics may be tightly related with the accretion process. |
| Guainazzi | The X-ray view of compact radio galaxies: new clues on the origin of the radio power in the Universe | M.Guainazzi, A.Siemiginowska | Parsec-scale extragalactic radio sources are believed to be compact because they are young. Common wisdom suggests that they represent the early stages in the life of large-scale radio structures. In this talk we will review the main results of our recent Chandra and XMM-Newton programs aiming at observing sizeable, complete samples of compact radio AGN. The results of these campaigns bear an impact on several aspects of our understanding of past, present and future in these sources: the physical processes responsible for their Spectral Energy Distribution; the influence of the ambient gas where the baby jets evolve on their growth; the duty cycle of their radio activity; and the ultimate fate and endpoints of their evolution. |
| Gupta | none | none | none |
| Haardt | |||
| Heckman | The Co-Evolution of Bulges & Black Holes | Timothy M. Heckman | I will review observations of the connection between the growth of black holes and the star formation history of the central few-kpc-scale region in early type galaxies in the local universe. I will discuss clues as to the fueling mechanism(s) for the black hole and comment on the nature of feedback that is related (either directly or indirectly) to the growth of the black hole. |
| Hovatta | Connection between jet parameters and black hole masses in quasars | T. Hovatta, E. Valtaoja, J. Tammi, M. Tornikoski, J. Torrealba, V. Chavushyan, T. Arshakian, I. Cruz-Gonzalez | A large sample of active galactic nuclei has been observed at
Metsähovi Radio Observatory, Finland, for the past 30 years at 22 and 37 GHz. Using these total flux density observations, we determined Doppler boosting factors for 87 sources. In addition, we obtained apparent speed data for 67 sources from the MOJAVE project and calculated Lorentz factors and viewing angles for these sources. We found that quasars are more Doppler boosted and have faster jets than BL Lacertae objects, and that almost all the sources are seen at a viewing angle of less than 20 degrees. In this work we have studied the connection between the jet parameters and black hole masses of 45 sources obtained from optical line-width measurements with two 2.1 metre telescopes of Universidad Nacional Autónoma de México. Our preliminary results show a negative correlation between the black hole mass and the viewing angle, which could be an indication of a wind-like component in the broad line region of these sources. |
| Hungwe | none | none | none |
| Ilic | Possible Outflow in the Broad Line Region of Active Galactic Nuclei | D. Ilic, L. C. Popovic, J. Leon-Tavares, A. I. Shapovalova, V. H. Chavushyan | The structure of the broad line region of active galactic nuclei (AGN) can be very complex. Different models have been proposed to explain the kinematics of the BLR (e.g. disk, spherical region, bi-conical outflows, etc.), but none so far has provided a self-consistent framework for explaining the observed properties of the broad emission line (BEL) profiles. Here we discuss the possibility that an accelerating outflow can affect BEL profiles. We found that in some AGN (as e.g. Mrk 668 and NGC 4151) the outflow model can well describe the line profiles in different epochs. |
| Ishibashi | Clumpy accretion flows in Active Galactic Nuclei | W.Ishibashi & T.J.-L. Courvoisier | We discuss the fueling of the central black hole in AGN in the framework of a clumpy accretion flow.
Shocks between elements (clumps) forming the accretion flow are at the origin of the observed radiation. We expect a cascade of shocks, with optically thick shocks giving rise to optical/UV emission and optically thin shocks accounting for the X-ray emission. The resulting blue bump temperature is found to be similar in objects of different luminosities. We obtain an X-ray to UV luminosity ratio always smaller than unity and lower values in massive objects compared to less massive sources, consistent with the observed alphaOX-LUV anticorrelation. We derive a characteristic X-ray variability time scale within our model and compare it with the observed X-ray PSD break time scale. The predicted dependence of the variability time scale on black hole mass and accretion rate is in agreement with the observational relation obtained by McHardy et al. (2006). |
| Kapinska | Birth and evolution of radio galaxies | A.D. Kapinska, P. Uttley, C.R. Kaiser | FRII radio galaxies are relatively simple systems which can be used to determine the influence of jets on their environments. Even simple analytical models of FRII evolution can link the observed lobe luminosities and sizes to fundamental properties such as jet power and density of the ambient medium; these are crucial for understanding AGN feedback. However, due to strong flux selection effects interpreting FRII samples is not straightforward. To overcome this problem we construct Monte Carlo simulations to create artificial samples of radio galaxies. We explore jet power and external density distributions by using them as the simulation input parameters. Further, we compute radio luminosity functions and fit them to the observed data, that cover redshifts up to z~2. This allows us to find the most plausible distributions of FRIIs' fundamental properties, but also to set more precise limits on the size cut-off and to discuss the possibility of FRII evolution into FRI objects. |
| Kauffmann | Differences between radio-loud and radio-quiet AGN: the view from SDSS | Kauffmann, Best,Donoso,Heckman | Using the unprecedentedly large samples of galaxies with spectra provided by the Sloan Digital Sky Survey, we
have been able to build catalogues of optically-selected and radio-selected AGN containing ~10^4 objects. We have been studying the differences in host galaxy properties and environments between the two classes of object, in an attempt to understand the different roles radio-quiet and radio-loud AGN may play in influencing the formation of their host galaxies. Most recently, we have extended this work out to redshifts of z~0.6. I will present new results based on a sample of 15,000 radio loud galaxies from the SDSS/2SLAQ catalogue of luminous red galaxies. There are 6000 SDSS quasars (around 600 of them radio-loud) in the same area of sky and redshift range. This permits us to carry out a detailed and statistically robust analyses of the luminosity functions and clustering differences between the different populations. I will discuss implications for Unified models. |
| Kawakatu | High-z Quasar formation under coevolution of SMBHs and circumnuclear disks | Nozomu Kawakatu | Based on a new physical model of a supermassive black hole (SMBH)
growth via gas accretion in a circumnuclear disk (CND). I will discuss the formation of high-z (z > 6) Quasars whose BH masses are >10^9M_sun. In the model, the mass-supply from a host galaxy and angular momentum transfer due to turbulent viscosity driven by supernova explosions in the CND are self-consistently considered. I will show the necessary conditions to form quasars at z > 6, in terms of the total accreted gas mass from host galaxies and star formation efficiency in the CND. I will discuss how these constraints impact on the physical processes of mass accretion from the galactic scale. Based on the model, I will also predict observable properties of quasars at z >6. |
| Kellermann | The Acceleration and Collimation of AGN Jets | K. I. Kellermann for the MOJAVE Collaboration | High resolution radio observations made as close as 0.1 pc to the central engine give unique insight into the region where AGN jets are accelerated and collimated into highly relativistic flows. Analysis of 13 years of VLBA MOJAVE observations indicates flows with typical Lorentz factors near 10, but ranging from near unity up to about 50, often with pronounced changes in direction and speed and with apparent variations in velocity across the jet flow. Fermi-detected quasar jets have faster flow velocities than the non gamma-ray jets,
Although the jet flows generally follow pre-existing, often twisting, paths, there is also evidence for ballistic flow, characteristic of ejection from a rotating nozzle. There is little or no evidence for real inward flow as might be observed from reverse shocks, but slowly moving or possibly stationary features in rapidly flowing jets are sometimes seen, and the final jet collimation may occur as much as a kpc or more from the jet origin. |
| Kelly | What is the Source of the Fluctuations in AGN Optical Flux? | Brandon Kelly, Jill Bechtold, & Aneta Siemiginowska | We analyze a sample of optical light curves for 70 quasars which have black hole mass estimates. We find that the characteristic time scales strongly correlate with black hole mass, and are consistent with disk orbital or thermal time scales. In addition, the amplitude of short time scale variations is significantly anti-correlated with black hole mass. We interpret the optical flux fluctuations as resulting from thermal fluctuations that are driven by an underlying stochastic process, such as a turbulent magnetic field in the accretion disk. In addition, the intranight variations in optical flux implied by our empirical model are consistent with current microvariability observations of radio-quiet quasars. Our stochastic model is therefore able to unify both long and short time scale optical variations in radio-quiet quasars as resulting from the same underlying process, while radio-loud quasars have an additional variability component that operates on time scales < 1 day. |
| King | Black Hole Feedback in AGN | Andrew King | The M-sigma and black hole - bulge mass relations show that galaxies know all about their central black holes. The cause seems to be that at typical Eddington ratios the holes produce momentum-driven outflows which cut off accretion when the black hole reaches the critical mass. I examine why this seems to be the usual case, and consider an important situation where it is not. |
| Kovalev | The relation between AGN gamma-ray emission measured by Fermi and parsec-scale radio jets | Y. Y. Kovalev for the MOJAVE collaboration | A list of 205 bright gamma-ray objects was recently reported using data
from the Large Area Telescope (LAT) on board the Fermi GRST. Comparison of the LAT positions with accurate radio positions of a VLBI-selected sample of extragalactic jets finds a total of 112 radio - gamma-ray counterparts including six new associations. Further comparison of VLBA observations of AGN parsec-scale radio emission with their associated gamma-ray properties shows that they are closely related. In the radio, gamma-ray bright sources are found to be brighter and more compact, suggesting that they might have higher Doppler factors than other blazars. The correlations found between the temporal radio and gamma-ray variability suggest that the prominent flares in both bands are produced in the parsec-scale cores, typically within an apparent time separation of up to a few months. These results indicate that relativistic beaming of the jet emission is important in both the radio and gamma-ray bands. |
| Koziel-Wierzbowska | none | none | none |
| Kudryavtseva | Jet wiggling in the BL Lac object 1803+784 from polarization observations | N.A. Kudryavtseva, D.C. Gabuzda, I. Arka | We present the results of very long-baseline interferometry polarization observations of the BL Lac object 1803+784 made simultaneously at 22 and 8 GHz at three epochs and at 22, 15, 8 and 5 GHz at one epoch in July 1998. We discuss motion of the jet components as well as spectral index and rotation-measure distribution. We find that the jet ridge line gradually changes position with time with a possible cycle of about 3 years. Changes of the jet position correlate with changes of flux density, degree of polarization, polarization angle, spectral index, and rotation measure of the jet components. We discuss possible theoretical explanations such as standing wave evolution or jet precession. |
| Labita | Downsizing of supermassive black holes from the SDSS quasar survey: The RLQ-RQQ differentiation | M. Labita, R. Decarli, A. Treves, R. Falomo | We have proposed a procedure to study the dependence on z of the BH mass for large samples of quasars, overcoming the problems related to the Malmquist bias (Labita et al.~2009, astro-ph/0903.4136). The scheme analysis was applied to the RQQ-dominated sample of ~50000 quasars from the SDSS for which MgII line width and 3000 A flux are available (0.35<z<2.25). The results are compared here with those obtained applying the procedure to a subsample of ~3000 RLQs. We find that RLQs are on average more massive than RQQs at low redshift, and suggest that this difference fades out at z~3. We discuss the BH mass gap in terms of different colors of the continuum in RLQs and RQQs, within a Shakura-Sunyaev accretion disc model. An alternative interpretation is based on the possibility that there is no intrinsic difference in the z-dependence of the two populations, and that the observed differentiation is due to a stronger radiation pressure in RLQs than in RQQs (Marconi et al.~2008). |
| Lee | Compact radio jets on sub-parsec scales | Sang-Sung Lee, Andrei Lobanov, Thomas Krichbaum, Arno Witzel, Anton Zensus | The VLBI cores of the compact radio sources are optically thick
at a given frequency. The distance of the core from the central engine is inversely proportional to the frequency (Koenigl 1981). Under the equipartition condition between the magnetic field energy and particle energy density, the absolute distance of the VLBI core can be predicted. From the database of VLBI surveys at lower frequencies (2, 8, 15, and 43,GHz) and that of the 3mm VLBI survey (Lee et al. 2008), the brightness temperatures in the rest frame are investigated in the sub-parsec regions of the compact radio sources. From the vicinity of the central engine, the brightness temperatures increase slowly and then rise with steeper slope. This implies that the jets are collimated and accelerated by the magnetically driven force, as predicted by Vlahakis and Koenigl (2004). |
| Leon-Tavares | Relativistic plasma as the dominant source of the optical continuum in the radio-loud galaxy 3C 390.3 | Arshakian T.G., Leon-Tavares J., Lobanov, A., Chavushyan V., Shapovalova A., Zensus J. A. | The localization and exact mechanism of the energy release in active galactic nuclei (AGN) are still not well understood because of complex structure of the nuclear region in AGN and
limited resolution of astronomical instruments. High-resolution radio observations of the radio galaxy 3C 390.3 during a period of 14 years allowed to resolve the nuclear region on subparsec-scales and to study the detailed kinematics of the jet. Here we present observational evidence for a link between appearances of new bright knots in the jet and the variable optical continuum emission in 3C 390.3. We interpret this correlation as evidence for the non-thermal optical flares generated in the innermost part of the jet via synchrotron continuum emission in the wide range of frequencies from radio to X-ray. |
| Liuzzo | Parsec-scale properties of Brightest Cluster Galaxies (BCGs). | Elisabetta Liuzzo | BCGs are a unique class of objects being the most luminous and massive galaxies in the universe. At present it is not clear if radio properties of BCGs in cool core clusters are systematically different from BCGs in merger clusters. Recent results suggest that the radio loud AGN could arrest or slow down the cooling process to supply the necessary energy as the presence of X-ray cavities in the emitting gas coincident with the presence of radio lobes indicates. I will present the results of my study on the pc properties of a sample of BCGs in Abell Clusters. We found that most BCGs in cool core clusters show a two-sided pc scale jet structure suggesting the presence of sub-relativistic jets. On the contrary jets in BCGs in non cool core clusters are mostly one-sided because of Doppler boosting effects. The different jet properties could be due to a different jet origin or to the interaction with a denser ISM in BCGs at the center of cooling clusters. |
| Lobban | The Suzaku View of the Low Luminosity Seyfert Galaxy, NGC 7213 | A.Lobban, J.Reeves, D.Porquet, P.Uttley, V.Braito, L.Miller, J.Turner | We present the results of the very first observation of the nearby (z = 0.005839) low-luminosity AGN NGC 7213 with Suzaku. X-Ray spectroscopy showed that narrow K-alpha emission from neutral and highly-ionised iron was clearly present yet no significant Compton reflection component was observed confirming the findings from previous Chandra and XMM-Newton/BeppoSAX observations. The lack of reflection suggests that the iron line complex is not produced in a Compton-thick material such as the disk or torus but instead could perhaps originate in a Compton-thin gas such as the BLR. No He-like resonance line was detected indicating that the ionised emission does not originate in collisionally ionised material; a view which is strengthened by the possible detection of the He-like forbidden line suggesting that the emission could instead originate from low-density photo-ionised material. An alternative suggestion is that this emission is actually originating from less-ionised material. |
| Macchetto | none | none | none |
| Macchetto | none | none | none |
| Madejski | Fermi LAT measurements of blazar spectra and implications on the source | Greg Madejski, for the Fermi LAT collaboration | Fermi Gamma-ray Observatory has been launched successfully and is
providing excellent data for jet-dominated active galaxies. The broad bandpass of Fermi's Large Area Telescope covers nominally the range of 0.03-300 GeV, and allows for good spectral measurements. This presentation covers the general properties of spectra of blazars. In some cases, at least for the bright and luminous sources, those spectra are complex: the LAT data often indicate steepening towards higher energies. An example is the gamma-ray - bright quasar 3C454.3, where the spectrum can be well-described by a broken power law, with the break at about 2 GeV and the index increasing by ~ 1, not consistent with a simple cooling break. We consider the origin of the break, and conclude that the absorption due to photon-photon pair production is unlikely. Rather, this spectral feature is most likely due to an intrinsic break in the distribution of the radiating electrons. |
| Majumdar | none | none | none |
| Malzac | Jet disc coupling in black hole binaries | Julien Malzac | As small-scale analogues of AGN, the study of accretion/ejection processes in stellar mass black holes appear useful to understand their supermassive cousins. I discuss the structure of the accretion flow in black hole binaries and the intrinsic connection between the hot comptonizing corona and radio jet. Focussing on the prototypical source Cyg X-1, I show that the current estimates of the jet power set interesting constraints on the jet velocity and the nature of the X-ray emitting region. I also show that in the hard state, the coronal magnetic field is below equipartition with radiation (suggesting that the corona is not powered by magnetic field dissipation). Moreover, the ion temperature in the corona is significantly lower than what predicted by ADAF like models. Finally I discuss the complex rapid (1s) optical X-ray correlation discovered in several sources that are best interpreted as a signature of jet/corona coupling. |
| Marshall | Possible Variability in the Jet of Pictor A | Herman L. Marshall and Martin Hardcastle | Pictor A is a nearby, powerful radio galaxy of the Fanaroff-Riley type II class. The jet is unusually narrow and well collimated with an opening angle of about one degree over much of its 100 kpc length. The bright lobes and large physical extent indicate that the jet is not closely aligned to the line of sight, so the jet X-ray emission is thought to arise from synchrotron emission rather than inverse Compton scattering of microwave background photons. The cross-jet extent is of order kpc, as found by Wilson et al. (2001). However, we find marginal evidence for variability between two observations taken less than two years apart. If confirmed, this variability would indicate that the X-ray emission is spatially concentrated into regions x1000 smaller than the width of the jet. |
| Max-Moerbeck | Two years of monitoring of blazars with the OVRO 40 m telescope at 15 GHz in support of Fermi-GST | Max-Moerbeck, Walter, Pavlidou, V., Pearson, T. J., Readhead, A. C. S., Richards, J., Stevenson, M., Healey, S. E., Romani, R. W., Shaw, M., Zensus, J. A., Fuhrmann, L., Angelakis, E. | We have continued the monitoring program of ~1200 sources with the Owens Valley Radio Observatory 40 m Telescope. Most of the sources are part of the Candidate Gamma-Ray Blazar Survey (CGRaBS). We have also been observing ToO triggered by gamma-ray detections and participating on multiwalength campaigns leaded by Fermi-GST. Regular program sources are observed twice a week and have been observed for ~24 months at a frequency of 15GHz. We use these light curves to study the radio variability, its relation with optical properties. A significant fraction of the bright AGNs detected by Fermi-GST are in our program which will allow for correlations between the radio and gamma-ray behavior for a number of sources. |
| Mazin | MAGIC observations of AGNs: scientific highlights | D. Mazin for the MAGIC collaboration | The MAGIC telescope, located on the Canary Island of La Palma, explores the universe in gamma-rays with energies from 50-60 GeV up to tens of TeV. Roughly 40% of the MAGIC duty cycle is devoted to observation of active galactic nuclei (AGNs), in which supermassive black holes are believed to be responsible for particle acceleration. By measuring of gamma-rays from these sources one can study nonthermal processes in plasma jets and fundamental properties of the black holes as well as questions of
the general physics and cosmology. In this talk, I will present highlights of MAGIC observations of AGNs in the last two years. I will also discuss physics consequences of the new discoveries concerning the production site of VHE gamma-rays in M87, the emission mechanism of gamma-rays in Mrk 421, limits on the quantum gravity scale from a flare in Mrk 501, and limits on the VHE gamma-ray horizon derived from the energy spectrum of 3C 279. |
| Medvedev | Are AGN jets baryon- or lepton-rich? | MIkhail V. Medvedev | A recent discovery of the generation of small-scale magnetic fields during reconnection in electron-positron plasmas opens up a fascinating opportunity to spectrally distinguish these sites of internal dissipation in magnetized jets with large leptonic abundance via the emitted jitter radiation. I will discuss the model and draw attention to observational predictions that can be used in the analysis and interpretation of observational data of emission from hot spots and knots in AGN jets. |
| Mehdipour | XMM-Newton high resolution X-ray spectroscopy of NGC 3516 | Missagh Mehdipour & Graziella Branduardi-Raymont | We present a new analysis of the soft and medium X-ray spectrum of the Seyfert 1 galaxy NGC 3516 taken with the RGS and the PN camera on board XMM-Newton. We examine four observations made in October 2006. The source shows significant flux variability between observations. We analyse the spectra of each observation separately to uncover how much of the observed variability is due to absorption by the warm absorber and how much is intrinsic to the source emission. The warm absorber is found to consist of three phases of ionisation, two of which have outflow velocities of more than 1000 km/s. The third phase (the least ionised one) is much slower at 100 km/s. It has previously been suggested that the passage of a cloud in front of the source caused a significant dip in the lightcurve during one of the observations. We however show that intrinsic changes in the source continuum play a much more significant role in explaining the observed flux and spectral variability than originally thought. |
| Mensah | none | none | none |
| Merloni | A synthetic view of AGN evolution and supermassive black holes growth | A. Merloni and S. Heinz | In the last decade, a combination of high sensitivity and spatial resolution observations and coordinated multi-wavelength campaigns have allowed substantial progresses towards super-unification schemes for active galactic nuclei, in which the large variety of different AGN classes can be classified based on fundamental physical parameters only, such as mass, accretion rate and kinetic energy output. I will describe the constraints available from a study of AGN evolution synthesis models on the growth of the SMBH population in the two main 'modes' observed (kinetic- and radiatively-dominated, respectively). I'll show how SMBH mass function evolves anti-hierarchically and I will also derive tight constraints on the average radiative efficiency of AGN. Finally, constraints on the redshift evolution of the AGN kinetic luminosity function will be discussed, thus providing a robust physical framework for phenomenological models of AGN feedback within structure formation. |
| Migliori | The X-ray view of the Compact Steep Spectrum quasar 3C186 | G. Migliori, A. Siemiginowska, A. Celotti | We present a complete study on the Compact Steep Spectrum (CSS) quasar 3C186. The X-ray spectral analysis based on a new Chandra observation leaves the origin of the X-ray emission undefined. We discuss the possibility that the X-ray emission is originated in the extended components, jets hotspots and lobes, applying the models for the X-ray emission currently adopted for the giant radio sources.
The broadband Spectral Energy Distribution and the peculiarly high radio loudness of the source are also analyzed in the frame of the evolution of radio sources. |
| Miller | Winds from AGN seen in X-ray absorption | L.Miller | Long Suzaku, XMM and Chandra X-ray observations of local AGN allow us to follow their spectral variations, revealing both continuum variations indicative of partial covering absorbers and absorption signatures from multiple zones covering a wide range of ionisation and outflow velocities. These variations are most clearly illustrated in recent analyses of MCG-6-30-15 and Mrk 766. When combined with broad-band information up to 50 keV on other AGN this points to a general picture where absorption by clumpy outflowing gas dominates what we see. We suggest that winds originating from the accretion disk are responsible and we discuss recent attempts to model the radiative transfer through accretion disk winds. |
| Mizuno | Stability of Magnetized Relativistic Jets | Y. Mizuno, P. E. Hardee, Y. Lyubarsky, & K.-I. Nishikawa | We investigated the stability of magnetized relativistic jets through 3D RMHD simulations. First we investigated the stability of magnetized spine-sheath relativistic jets against Kelvin-Helmholtz (KH) instability. We found that destructive KH modes can be stabilized even when the jet Lorentz factor significantly exceeds the Alfven Lorentz factor. Even in the absence of stabilization, spatial growth of destructive KH modes can be reduced by the presence of mildly relativistic sheath flow around a relativistic jet spine. Second we studied the development of current-driven (CD) kink instability of a static force-free helical magnetic field configuration. We found that the initial configuration is strongly distorted but not disrupted by CD kink instability. The linear growth and nonlinear evolution of the CD kink instability depends on the radial density profile and strongly depends on the magnetic pitch profile. We also discuss with the effect of flow on a CD kink instability. |
| Nagamine | none | none | none |
| Nalewajko | Polarization of emission from reconfinement shocks | Krzysztof Nalewajko & Marek Sikora | We model polarization of synchrotron emission from relativistic reconfinement shocks expected to form in lowly magnetized jets interacting with external medium. We consider both chaotic and ordered (toroidal) magnetic fields. We show that perpendicular polarization with degree up to 30% can be obtained from chaotic magnetic fields compressed at the shock fronts, only when the upstream flow is divergent. Net parallel polarization is obtained, if the jet is highly relativistic and the observer is located within the jet opening cone, or by increasing the toroidal component of magnetic field. |
| Narayan | MHD Simulations of Relativistic Jets | Ramesh Narayan, Alexander Tchekhovskoy, Jonathan McKinney | Will be submitted later |
| Ohsuga | Global Radiation-Magnetohydrodynamic Simulations of Black Hole Accretion Flow and Outflow: Unified Model of Three States | Ken OHSUGA | We have for the first time succeeded in performing global radiation-magnetohydrodynamic (RMHD) simulations of black-hole accretion flows and outflows. Our simulations reproduce three distinct modes of accretion flow (slim state, standard state, RIAF state) and outflow. The disk with higher mass-accretion rate becomes thick via strong radiation pressure and it’s luminosity exceeds the Eddington luminosity (slim). The cool and thin disk forms via effective radiative cooing in the case of moderate mass-accretion rate (standard). The disk consists of hot rarefied plasmas when the mass accretion rate is very small (RIAF). The disk outflows with helical magnetic fields, which are driven either by radiation pressure or magnetic pressure, are ubiquitous in any modes. They can explain the blue-shifted absorption features and polarized emission in AGNs and BHBs. Our RMHD simulation can open a new era of accretion disk research and provide a unified view of accretion flows in various contexts. |
| Oozeer | MRC 1925-296, a Wide Angle Tail radio source (WAT): Preliminary results. | Oozeer N | We have observed MRC 1925-296 using the Giant Metre Wave Radio Telescope (GMRT) at 618 MHz. We classify MRC 1925-296 as a wide-angle tail radio galaxy (WAT) with a rather asymetric morphology in extent with respect to the radio core. This asymetric morphology is consistent with the idea that WAT can be
used as tracers of clusters. The host galaxy for MRC 1925-296 is coincident with an E+4 galaxy (ESO 192508-2937.9) of r magnitude 13.83, z=0.02455. There are two bright optical galaxies in the field that are separated by around 56 kpc and they seem to have started interaction. Using multi-frequency data, we derived radio properties of the source and show that there evidence for an ongoing galaxy-galaxy interaction/merger within this young WAT. From the 2MRS, it seems more likely that MRC 1925-296 belongs to a group or sub-cluster with 8 member candidates. However, from the6dfGS DR3 we revealed more new sources within this sub-group with similar redshift. |
| Orienti | Diffuse optical emission in radio hot spots | M. Orienti, M.A. Prieto, G. Brunetti, K.-H. Mack | Hot spots are bright and compact regions located in the outermost part of powerful radio sources. These regions are considered the
"working surface" of supersonic jets in which kinetic energy is dissipated into the acceleration of relativistic particles. Optical emission from hot spots has been rarely detected, since high-energy optical electrons have short radiative lifetime. However, in low-power radio hot spots, where energy losses are less severe, an unprecedented high optical detection rate has been found. Furthermore, the optical emission is not compact, but extends over an area of several kpc. This discovery questions the standard shock model, implying that additional efficient acceleration mechanisms are at work. I will present new VLA and VLT observations of a sample of radio hot spots, and I will discuss the hot spot multi-band morphology and spectral energy distribution, two fundamental ingredients to constrain the physical processes at work in these cosmic accelerators. |
| O'Sullivan | Magnetic Field Strengths on Sub-Parsec Scales in Blazar Jets | Shane O'Sullivan and Denise Gabuzda | We use simultaneous, multi-frequency radio observations from the VLBA (Very Long Baseline Array) to probe the parsec to sub-parsec structure in six blazar jets (2200+420, 2007+777, 1749+096, 1418+546, 1156+295, 0954+658). From our measurements of the frequency-dependent shift of the synchrotron self-absorbed radio core, we calculate magnetic field strengths and other physical properties of these jets such as the total jet luminosity and the de-projected distance of the radio core from the base of the jet. We find magnetic field strengths of the order of 1 G in the 43-GHz (7-mm) cores. By extrapolating our results to the estimated jet launching regions, we approach magnetic field strengths of ~10^4 G at an inner accretion disk distance of ten gravitational radii. |
| Pacciani | Multiwavelength observations of the gamma-ray blazars of the Virgo Region | Luigi Pacciani | AGILE pointed the Virgo Region for 3 weeks starting from the 2nd half of december 2007. We detected two FSRQ: 3C 273 and 3C 279, and an unidentified EGRET source: 3EGJ1236+0457.
Simultaneous data were collected with REM, RXTE, INTEGRAL, and Swift for the two FSRQs. We observed gamma ray variability for all the sources. In particular, we found 3C 273 very bright in X-ray, allowing us to disentangle the Seyfert-like contribution from the jet emission. We compare the 3C 279 SEDs obtained from this period and from the multiwavelenght campaign of july 2007. We detected 3EGJ1236+0457 at a flux almost an order of magnitude higher than the mission averaged flux reported in the EGRET catalog. The deep exposure of INTEGRAL allows us to pose deep upper limit for the hard X flux of this source. We didn't detect the blazar 4C 04.42, obtaining for the 3 weeks of observation an upper limit comparable to the EGRET one, evaluated from the integration over all the EGRET dataset. |
| Paneque | Fermi view of the classical TeV High Peak BL Lacs | D.Paneque on behalf of The Fermi/LAT Collaboration | Despite High Peak BL Lacs (HBL) being observed for tens of years, the existing experimental data set is not sufficient to unambigously identify the physical mechanisms responsible for the electromagnetic emission. The Fermi/LAT instrument, which started operation in August 2008, provides "continuous" source coverage with high sensitivity in the band 0.1-100 GeV, which is rather unexplored for HBLs. In particular, the simultaneous observations of HBLs with Fermi/LAT and Imaging Cherenkov Telescopes (IACTs) have the unprecented capability of resolving the complete high energy bump on time scales of weeks and shorter for the brightest HBLs, which has the potential of breaking inter-model and intra-model degeneracies. In the conference I will report on the Fermi view of several classical TeV HBL sources, namely Mrk421, Mrk501, 1es1959+650 and PKS2155-304, all them being observed in the framework of multi-frequency campaigns, and preliminary implications will be given. |
| Panessa | The radio and X-ray coupling in radio quiet AGN | F. Panessa & M. Giroletti | Sensitive observations reveal that radio-quiet Active Galactic Nuclei (AGN) are not radio silent.
We have recently found a correlation between the nuclear 2-10 keV X-ray and radio luminosities for a well defined sample of local Seyfert galaxies, suggesting that the accretion flow and the radio source are strongly coupled. In these sources the accretion rate is linked to the radio-loudness, as expected in low luminosity AGN where an advection-dominated accretion flow (ADAF) is supposed to be coupled with a compact radio jet. However, the same correlation has been found also for high luminosity AGN where instead standard accretion thin disk is responsible for the high energy emission. We will present recent results on VLBI radio observations of very low luminosity AGN which had revealed an ubiquitous presence of sub-parsec cores and/or structures going down to sub-mJy flux densities. |
| Pashchenko | Giant Radio Sources | Komberg B.V., Pashchenko I.N. | Based on the miscellaneous published radio and optical data, SDSS and APM catalogue we consider the various properties of the giant radio sources (gRS) with the aim of refining the conditions leading to the formation of these objects. We compare gRSs with the regular-sized radio sources in radio and optical bands, yielding the results on the origin of their giant linear sizes, asymmetry of their radio lobes and the role of the environment
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| Pashchenko | Radio Induced Nuclear Activity in Neighbour Pairs of Galaxies | Pashchenko I.N., Komberg B.V. | We discuss possible AGN and SF activity in close pairs of galaxies where one of the companions is the radiogalaxy. Such close vicinity of the radio source could trigger activity in neighbour galaxy not only through interactions but also via direct action of the radio jet or wind. We use SDSS data to collect the sample of close pairs of galaxies and identify AGN and SF activity and FIRST data to select pairs of galaxies with radio sources. Fractions of AGN, radio loud galaxies and other properties of close pairs are considered and discussed in frame of different models of triggering AGN activity. |
| Pavlidou | Structure and emission models of blazar jets: making progress through large monitoring programs. | Vasiliki Pavlidou, Walter Max-Moerbeck, Tim Pearson, Antony Readhead, Joey Richards, Matthew Stevenson | The coming decade holds unprecedented promise for progress in AGN jet physics. Large-scale blazar monitoring efforts, such as the coninuous survey of the GeV sky by Fermi-LAT and the OVRO 40-m 15GHz monitoring program of more than 1,000 blazars, will significantly advance our understanding of blazar jets at the population level. We discuss tests based on the comparison of predictions made by different theoretical models for blazar jet properties and features of the high-energy and radio emission, with observations of large numbers of blazars. Using quantities that can be computed for a large number of objects and for which different models make distinct predictions, it is possible (a) to evaluate the relevance of different classes of models to different subclasses of the blazar population rather than for specific objects; and (b) to seek and identify different classes of gamma-ray–loud blazars, as well as different types of variability occuring in the same objects. |
| Perea | none | none | none |
| Petrucci | none | none | none |
| Polletta | Dissecting AGN Spectral Energy Distributions: obscuration and host contribution | Mari Polletta, Laura Maraschi, Lucio Chiappetti, Ginevra Trinchieri, Marco Giorgetti | The X-ray-far-infrared spectral energy distributions of an X-ray selected sample of AGN are modeled with an AGN and a host component in order to examine the host properties, and the AGN obscuration in AGN of different type and luminosity. The sample includes hundreds of AGN covering 2 dex in luminosity at z=0.2-3. Overall, the AGN is obscured in type 2 AGNs and is not obscured in type 1 AGNs, as expected. AGN with no clear AGN signature in their optical-infrared spectral energy distributions are characterized by hosts that are more luminous than the AGN and by a broad range of extinction values. The host and the AGN luminosities are compared in AGN of various types. The observed trends are compared with the predictions of current AGN evolutionary models.
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| Porquet | none | none | none |
| Pounds | How energetic are the fast ionised outflows in AGN? | Ken Pounds | While initially disputed, the evidence for sub relativistic outflows of highly ionised gas from several luminous AGN is now strong. However, to translate the deduced outflow velocities into mass and energy rates requires knowledge of the collimation and covering factor of the outflow. Recent and archival XMM-Newton observations of the luminous Seyfert PG1211+143 are re-examined and compared with photoionisation models, finding evidence that the outflow does carry mechanical energy at a rate to potentially disrupt star formation. |
| Prandini | none | none | none |
| Prandoni | The AGN component in radio deep fields | I. Prandoni et al. | AGNs have recently been recognized as contributing in significant numbers to the radio source counts at sub-mJy flux densities, but still controversial are their physical and evolutionary properties. One of the key unresolved issues is whether, as a function of cosmic epoch, the low-power AGNs are more related to efficiently accreting systems (mostly radio-quiet) or to systems with very low accretion rates (mostly radio-loud). We are currently exploiting the multi-wavelength information available for several deep radio fields to investigate the physical properties of faint radio-selected AGNs. I will here focus on the ATESP-DEEP1 field and the First Look Survey. Our results clearly shows that the large majority of low power AGNs are radio-loud, possibly associated to jet-dominated, low accretion rate systems. Very interestingly, however, we have also a first direct evidence of the presence of radio-quiet AGNs at sub-mJy flux levels. |
| Prieto | High spatial resolution spectral-energy-distributions of radio-quiet vs radio-loud AGN | M. A. Prieto | We present high spatial resolution SEDs, on the scales of a few tens of parsec, of some of the nearest and most well known, radio-quiet AGN. The new SEDs are found to largely depart, in shape and bolometric luminosity, from those compiled from large aperture IR satellite data.
Type 1/2 radio quiet AGN can clearly be identified by the overall shape presented in these new SEDs. A further comparison of these with the SED of the radio loud prototype 3C 273 reveals major differences with type 2 radio quiet objects at almost any wavelength but a few similarities with type 1s, mainly in the optical and the soft X-rays. A new major difference arises however in the mid- to far- IR between the two groups, which we tentatively ascribe to different dust size composition. |
| Proga | Dynamics of Accretion Flows and Outflows in AGN | Daniel Proga | I review the results from multi-dimensional, time-dependent simulations of
gas dynamics in AGN. I will focus on two types of outflows powered by radiation emitted from the AGN central engine: (i) outflows driven from the innermost part of an accretion disk and (2) outflows driven from a large-scale inflow that is likely the main supplier of material to the central engine. I discuss the relevance of both types of outflows to the so-called AGN feedback problem. However, the AGN feedback should not be considered separately from the AGN physics. Therefore, I also discuss the issue whether the properties of the same outflows are consistent with the gas properties in broad- and narrow-line regions. |
| Pursimo | Spectroscopic identification of the MASIV 5 GHz VLA Scintillation Survey | Tapio Pursimo, Roopesh Ojha, David Jauncey, Jim Lovell, Barney Rickett, J-P Macquart, Hayley Bignall, Lucyna Kedziora-Chudczer, Mike Dutka, Cliff Senkbeil, Stas Shabala | The MASIV 5 GHz VLA flat-spectrum radio source variability survey of the northern sky has discovered that more than 50% of the 475 targets exhibited inter-stellar scintillation (ISS) on one or more of the four survey epochs. We present the first results of the spectroscopic identifications of the sample. For 255 sources the spectroscopic id is from the literature and for 75 using our own data. The targets are classified as QSOs, BL Lac objects or AGN, based on their optical spectrum and luminosity. The majority of the targets are QSOs, however there are many BL Lac objects and some AGNs. The BL Lac fraction appears to be much higher amongst the ISS than non-ISS sources and most AGNs are non-ISS sources. These results suggest that ISS sources have flat redshift distribution in comparison to the non-ISS, also there is a lack of z>2 ISS sources. In the optical, ISS sources have narrower brightness distribution than non-ISS and they are about 0.5 magnitudes fainter on average. |
| Raiteri | Multifrequency observations of BL Lacertae in a faint state: the quest for accretion disc signatures | C.M. Raiteri, M. Villata, A. Capetti, for the WEBT consortium | BL Lacertae was the target of a multifrequency campaign organized by the Whole Earth Blazar Telescope in the 2007-2008 observing season.
The source was monitored in the optical, near-IR and radio bands by tens of observers around the globe, while optical spectra were taken at the TNG and 2.1 m GHAO telescope in Mexico. Optical-UV and X-ray information was acquired through 3 pointings by XMM-Newton. We here present the results of this intensive observational effort. |
| Ramirez | THE NATURE OF THE NEAR-IR CORE SOURCE IN 3C 433 | Edgar A. Ramirez, C. N. Tadhunter, D. Axon, D. Batcheldor, S. Young, C. Packham and W. B. Sparks | We report the analysis of NIR imaging, polarimetric and spectroscopic observations of the powerful radio galaxy 3C433, obtained with the HST and UKIRT telescopes.
Our analysis reveals:(1) the presence of a dust lane aligned close to perpendicular to the radio jet axis; (2) a steep slope of the NIR SED; (3) The absence of a broad Pa alpha emission line; (4) high polarization for the unresolved core nuclear source, with an E-vector perpendicular to the radio jet. Using four independent techniques we determine an extinction to the compact core source in the range 3<A_V<51 mag. The analysis rules out a synchrotron origin for the NIR polarization of the compact core source. Dichroic extinction is perhaps the most plausible polarization mechanism, over scattering, as it is consistent with the various available extinction estimates. In this case, a highly ordered toroidal magnetic field must be present in the obscuring structure close to the nucleus. |
| Raue | Discovery of VHE gamma-ray emission from Centaurus A with H.E.S.S. | M. Raue et al. for the H.E.S.S. Collaboration | Centaurus A is the closest active radio galaxy. Its proximity enables unique studies of the processes in relativistic jets and near supermassive black holes. Centaurus A has been intensively studied in many wavelength bands and has also been discussed as a possible site for UHECR acceleration. Here, we report the discovery of weak very-high energy gamma-ray emission from Centaurus A with the H.E.S.S. Cherenkov telescope array. The discovery of Centaurus A, together with the detection of M 87, establishes radio galaxies - i.e. AGNs with only weak relativistic beaming - as sources of VHE gamma-rays. The implications of these results on the emission site and on the different models available will be discussed. |
| Reeves | Compton Thick Winds in Type I AGN | James Reeves | Here I discuss evidence for near Compton-thick outflows in luminous type I AGN, which may originate from the inner accretion disk wind. In particular I discuss evidence from Suzaku in the type I quasar PDS 456, for a highly ionized outflow, with velocities measured from the iron K band of the order 0.25c, implying an origin from the innermost accretion disk. Drastic variations in the spectra of PDS 456 over the course of a decade are likely due to changes in the line of sight covering fraction of the disk wind. High column density absorption may also be present in the radio-quiet quasar 1H 0419-577 and the NLS1 NGC 4051, which both show strong excesses in flux in the hard X-ray band with Suzaku HXD. However such components are not detected thus far in radio-loud AGN, suggesting a dichotomy in the production of winds/jets between radio-quiet/radio-loud AGN. Finally we discuss whether the disk winds can contribute significantly to cosmic feedback in terms of their energetics. |
| Reichstein | Parsec Scale Analysis of Spine+Sheath Structures in AGN Jets | Andrea Reichstein and Denise Gabuzda | We will present multi-frequency radio observations from the Very Long Baseline Array (VLBA) of selected AGN, that seem to have a B-field structure with a central "spine" of B-field orthogonal to the jet and a longitudinal B-field near one or both edges of the jet. Two explanations for this structure have been discussed in the literature: shocks making the central orthogonal field combined with a jet-medium interaction making the "sheath" of longitudinal field, or both components produced by a helical jet magnetic field. We will discuss evidence from our observations supporting one or the other of these pictures. |
| Romano | Swift observations of gamma-ray quiet BL Lacs | P. Romano, S. Vercellone, B. Sbarufatti, V. La Parola | We present the preliminary results on a study of a small sample of gamma ray
quiet BL Lacs and flat-spectrum radio quasars. These objects were observed by Swift, whose broad-band spectral capabilities and pointing flexibility are best suited to examine any possible difference and/or similarity between the synchrotron to inverse Compton transition region of gamma ray loud and gamma ray quiet blazars. We present the spectral energy distributions of the sample and compare them with those of gamma ray loud blazars. |
| Ros | none | none | none |
| Sambruna | The disk-jet connection in X-rays: Suzaku view of Broad-Line Radio Galaxies | Rita Sambruna | We review our Suzaku observations of Broad-Line Radio Galaxies (BLRGs). The continuum above 2~keV in BLRGs is dominated by emission from an accretion flow, with little or no trace of a jet, which is instead expected to emerge at GeV energies and be detected by Fermi. Concerning the physical conditions of the accretion disk, BLRGs are a mixed bag. In some sources the data suggest relatively high disk ionization, in others obscuration of the innermost regions, perhaps by the jet base. While at hard X-rays the distinction between BLRGs and Seyferts appears blurry, one of the cleanest observational differences between the two classes is at soft X-rays, where Seyferts exhibit warm absorbers related to disk winds while BLRGs do not. We discuss the possibility that jet formation inhibits disk winds, and thus is related to the remarkable dearth of absorption features at soft X-rays in BLRGs and other radio-loud AGN.
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| Savolainen | On the intrinsic jet properties of the Fermi-detected blazars | T. Savolainen for the MOJAVE collaboration | It is possible to determine Lorentz factors and viewing angles of the AGN jets by combining VLBI measurements of the apparent jet speeds with Doppler factors estimated from their flux density variability. We have calculated these quantities for a sample of 66 northern blazars by using VLBA data from the MOJAVE survey and Doppler factors measured by the Metsähovi Radio Observatory quasar monitoring team. Comparison with the recently released Fermi LAT Bright AGN Sample shows that the gamma-ray bright quasars have on average higher variability Doppler factors than gamma-ray weak quasars, but not significantly different Lorentz factors. Interestingly, the LAT-detected sources have a significantly narrower distribution of jet rest-frame viewing angles than the general population: the values gather close to 90 degrees which suggests that gamma-photons leaving the jet at right angle have a shorter pathlength through the strong photon-field and are therefore less absorbed. |
| Sbarufatti | ESO VLT optical spectroscopy of BL Lac objects. | Sbarufatti B., Treves A., Decarli R., Kotilainen J., Ciprini S., Romano P., Falomo R. | We report results from our program of optical spectroscopy of BL Lacs performed with the ESO VLT under non optimal seeing conditions. We present here high S/N optical spectra of 32 candidates, providing a classification, new redshifts and spectral line statistics, or redshift lower limits in the case of featureless objects. |
| Schawinski | Do AGN Suppress Star Formation? | Kevin Schawinski | When star formation stops in blue star-forming galaxies, their stars evolve passively through intermediate colors ("the green valley") and then onto the red sequence. The high incidence of AGN in the green valley has been interpreted as evidence that AGN feedback is the process that suppresses star formation. Using new observations from the IRAM 30m and Swift BAT, I show that the role of AGN in the shutdown of star formation is much more complex than previously thought. I show that the luminous AGN whose host galaxies lie in the green valley turn on at least 100 Myr after star formation turns off, and thus cannot be responsible for its suppression. On the other hand, the molecular gas that fuels star formation is rapidly destroyed, possibly due to an earlier low-luminosity AGN phase. This suggests that there is a sequence of an early, weaker AGN phase, during which kinetic outflows might provide the most important feedback, followed roughly 100 Myr later by a more luminous AGN phase. |
| Schinzel | Three Decades of Very Long Baseline Interferometry Monitoring of the Parsec-Scale Jet in 3C 345 | Schinzel, F.K.; Lobanov, A.P.; Zensus, J.A. | The 16 magnitude quasar 3C 345 (redshift z=0.5928) shows structural and emission variability on parsec-scales around a compact unresolved radio core. It is an archetype for jet precession and has been closely monitored using VLBI techniques for the last three decades in order to increase our understanding of the physics behind relativistic outflows and dynamics of the central regions in AGN. I will present our long-term jet evolution analysis mostly based on the 15 GHz MOJAVE survey data collected over the last ~14 years and combined with data from earlier VLBI observations of 3C345 started in 1979. I will
discuss the trajectories, kinematics, and flux density evolution of enhanced emission regions embedded in the jet and present evidence for geometrical (e.g. precession) and physical (e.g. relativistic shocks and plasma instability) factors determining the morphology and dynamics of relativistic flows on parsec-scales. |
| Severgnini | none | none | none |
| Siemiginowska | Intermittent Activity | Aneta Siemiginowska et al | Large scale X-ray jets that extend to >100 kpc distances from the host
galaxy indicate the importance of jets interactions with the environment on many different physical scales. Morphology of X-ray clusters indicate that the radio-jet activity of a cD galaxy is intermittent. This intermittency might be a result of a feedback and/or interactions between galaxies within the cluster. Here we consider the radiation pressure instability operating on short timescales (<10^5 years) as the origin of the intermittent behaviour. We test whether this instability can be responsible for short ages ( ~10^3 years) of Compact Symmetric Objects measured by hot spots propagation velocities in VLBI observations. We model the accretion disk evolution and constrain model parameters that may explain the observed compact radio structures and over-abundance of GPS sources. We describe interactions between the jet and the ISM during consequent outbursts. |
| Singh | Radio and X-ray Emission from Low-luminosity AGNs | Veeresh Singh, Prajval Shastri, Guido Risaliti, Ramana Athreya | Seyfert galaxies are low-luminosity, radio-quiet Active Galactic Nuclei (AGN) powered by accretion on to supermassive black hole. The high-frequency radio observations of Seyfert galaxies show jet-like compact features, which tend to be confined within the host galaxy, whereas low-frequency radio observations of several Seyferts show more extended radio emission. We attempt to investigate the low-surface-brightness extended radio emission and its association to nuclear outflows for a rigorously selected sample of Seyfert galaxies in the framework of Seyfert unification hypothesis. The sample is based on orientation-independent parameters of the host galaxy as well as AGN and aimed to test the predictions of Seyfert unification hypothesis using multiwavelength observations. We shall present radio and X-ray studies based on GMRT and XMM-Newton observations for our sample of Seyfert galaxies. |
| Socrates | The Eddington Limit in Cosmic Rays | Aristotle Socrates | In terms of their energetics, cosmic ray protons are an insignificant by-product of star formation
and super-massive black hole growth. However, due to their small mean free path, their coupling with the interstellar medium is absolute. In fact, they are most likely the dominant source of momentum, and therefore kinetic force on galactic scales. By defining an Eddington Limit in cosmic rays, we show that the maximum photon luminosity of bright galaxies and quasars are capped by the production and subsequent expulsion of cosmic ray protons. Such simple arguments may explain why bright galaxies are faint in comparison to quasars and why super-massive black holes are relatively mass-less in comparison to galaxies. |
| Spoon | Mid-IR kinematic evidence for outflows in ULIRGs | Henrik Spoon | We report on the results of a first systematic study of the line
profiles of the mid-infrared fine-structure lines of Ne+, Ne2+, Ne4+ and Ne5+ (21-127 eV) in a sample of 200 ULIRGs, HyLIRGs, Seyferts, QSOs and starburst galaxies observed in the high-resolution mode (R=600) of Spitzer-IRS. The sources span a range of 5 decades in [NeV] AGN luminosity and 6 decades in 21cm radio luminosity. We detect resolved line emission in the majority of ULIRGs, most notably in those with an optical Seyfert classification. Comparison of the velocity line profiles of different ionization stages indicates a gradual increase of ionization with increasing blue shift for part of our sample, whereas for other sources all neon lines have similar profiles. We further find a correlation between the FW20 and the line luminosity for the [Ne III] and [Ne V] lines. ULIRGs, the radio-loud ones especially, appear to form the high-luminosity end of this correlation. |
| Stawarz | Radio quiet vs. radio loud AGN: what makes the difference? | L. Stawarz | We investigate how the total radio luminosity and the jet production efficiency of active galaxies depend on the accretion power, mass of a central black hole, and the type of a galaxy host. We argue that an another parameter in addition to the accretion rate must play a role in determining the observed radio properties of AGN, and that this parameter is related to the properties of host galaxies. In this context, we discuss the spin paradigm for the jet production by accreting supermassive black holes. |
| Sulentic | An Empirical (4DE1) Approach to the RL-RQ Dichotomy | J. Sulentic, S. Zamfir, P. Marziani | We have developed a 4D empirical formalism that emphasizes
correlations and differences between different types of AGN that show broad emuission lines. We confirm the physical reality of the RL-RQ dichotomy and suggest that it is driven by a combination of accretion rate and host galaxy morphology. In other words RL AGN are really different from radio-quiet/intermediate sources. Pre-SDSS and SDSSS spectroscopic samples are presented to support this interpretation. |
| Tagliaferri | none | none | none |
| Tammi | Thermal non-jet flares in quasars and microquasar | Joni Tammi & Talvikki Hovatta | We discuss the possibility of thermal flares near the compact objects in quasar/microquasar objects. In our model a fraction of collapsed accretion disc matter expands outwards from the central compact object and radiates mainly via free-free emission. By estimating the radiation spectra emitted by this expanding ''''wind'''', and comparing the results with long-term radio and optical lightcurves, we study the suitability of this kind of event causing the double-peaked flares observed in some microquasars and quasars. In this model only the second peak would be produced by the bright ''''knots'''' propagating in the jet; the first peak --with no corresponding jet feature found-- would be of thermal origin and produced in the very centre of the system and not in the jet. |
| Tavecchio | none | none | none |
| Tombesi | A search for relativistic outflows signatures in the X-ray spectra of radio-quiet AGNs | Tombesi F., Cappi M., Yaqoob T., Reeves J., Palumbo G.G.C. | Evidence for the presence of relativistic outflows in the inner regions of Seyfert galaxies have been claimed in recent years. These would indicate the existence of winds or ejection of material close to their super-massive black hole, possibly from the accretion disk. In particular, X-ray observations of several sources revealed the presence of absorption lines due to highly ionized iron with blue-shifted velocities of the order of 0.01-0.1c. We present preliminary results of an homogeneous analysis of a complete sample of local bright Seyfert galaxies observed with XMM-Newton. We performed a systematic search for blue-shifted absorption lines in their spectra, in the Fe K band (4-10 keV). This study will help to estimate the recurrence of such phenomena and to constrain several parameters, such as the composition and ionization state of the outflow, its overall energetic budget and kinematics. |
| Torresi | Traces of warm absorption in the Broad Line Radio Galaxy 3C 382 | E. Torresi, P. Grandi, G.G.C. Palumbo, M. Guainazzi, A.L. Longinotti, A. Nucita, F. Tombesi | In obscured Radio Galaxies (RGs) traces of photoionised gas were already revealed as emission lines in the soft X-ray spectra of 3C 445 and 3C 33, while no soft X-ray absorption structures have been detected in unobscured RGs yet. Here we present the first detection of soft X-ray absorption lines in a Broad Line Radio Galaxy.The resolving power E/ΔE≥200 of the Reflection Grating Spectrometer (RGS) on-board XMM-Newton, has allowed to reveal a component of highly ionised warm gas (logξ>2 with column density ~10^22 cm-2) in 3C 382 , analogous to the high-ionisation phase warm absorbers observed in Radio-Quiet (RQ) AGNs. This finding opens up an important and yet unexplored way for investigating Radio-Quiet and Radio-Loud (RQ/RL) dichotomy, through the comparison of their environment properties.
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| Tosti | Fermi/LAT observations of AGNs: First results | G. Tosti on behalf of the Fermi/LAT Collaboration | The Fermi Gamma-ray Space Telescope (formerly GLAST, launched June 11, 2008) is opening a new era for gamma-ray extragalactic astronomy. The Large Area Telescope (LAT), the main instrument aboard Fermi, with its wide field of view (>2sr) and large effective area allows to scan the entire sky every 3 hours with unprecedented sensitivity in the energy band from 20 MeV to >300 GeV. In the first months of science operations the fermi/LAT has already detected more than one hundred gamma-ray sources located away from the galactic plane (|b|>10) that can be confidently associated with known AGNs. Most of them are blazars that where not previously known at GeV energies. In this contribution we summarize the gamma-ray properties of these sources, their Log N - Log S distribution, and the resulting luminosity function.
Labels parameters Labels |
| Tramacere | The giant X-ray flares of Mrk 421 in spring-summer 2006, signature of stochastic acceleration synchrotron emission and jet energetics. | Andrea Tramacere | We present results from the analysis of Swift observations of Mrk 421. The X-ray spectrum is well described by a log-parabolic distribution close to the peak energy (Ep), with the peak flux of the SED (Sp) correlated with Ep, and Ep anti-correlated with the curvature parameter (b). The UV-to-soft-X-ray spectral shape of the most energetic flares requires a power-law electron distribution with a spectral index s ~ 2.3. The Ep-b trend is consistent with a stochastic acceleration scenario, whereas the power-law slope in the low energy branch is consistent with the relativistic shock predictions, hinting for the magnetic turbulence playing a twofold role: spatial and momentum diffusion. We find that the Sp-Ep trend is consistent with the flaring dynamic mainly driven by a change in the average particles energy, with a possible modulation of the number of particles as the luminosity approaches the value of 10^45 erg/s, hinting for a possible signature of the jet energetic budget. |
| Treves | none | none | none |
| Trussoni | Accretion and jet powers in low-power VCC radio galaxies | E. Trussoni, A. Capetti, S. Vattakunnel | Very recently it has been shown that in radio loud, non obscured
AGN a strict correlation exists between the accretion rate from the hot Intergalactic Medium (IGM) and the jet power, holding on many power decades (Allen et al. 2006, MNRAS 372, 21; Balmaverde et al. 2008, A&A 486, 119). In this framework we have analyzed, exploiting archive X-ray data of Chandra, the accretion properties of a small sample of low power early type galaxies (nine objects) members of the Virgo Cluster with two main aims: i) to check whether the correlation `hot accretion vs jet powers` holds down to very low radio luminosities, around the threshold radio loud-quite AGN; ii) to verify if and how the accretion process can be affected by different ambient properties, depending on the positions of the galaxies in the cluster. |
| Turner | New Results on the Importance of X-ray Absorption in AGN | T.J.Turner, L.Miller, J.N.Reeves | New data from Chandra, XMM and Suzaku has shown that X-ray absorption by partial-covering gas with high column density and ionization-state plays a significant role shaping spectral and flux variability in AGN. I discuss recent progress, highlighting some new results including those from NGC 3516 and 1H 0419-577. |
| Urrutia | Demographics of LoBAL Quasars | Tanya Urrutia | In the last few years we have been conducting a large survey program to find dust-reddened quasars. Follow-up imaging and Mid-IR spectroscopy showed that a high fraction (85%) of these quasars are in a merger phase and have LIRG-like star-formation rates leading us to believe that they are young, just-ignited quasars that are obscured by their merging host galaxies. It then came as a surprise that at high redshift a large number of these objects (~100 times more than in the SDSS) belonged to the class of Low Ionization Broad Absorption Line Quasars (LoBALs), with extremely high reddenings. I will speculate that these LoBAL quasars are in a young phase in which the quasar is accreting at high efficiencies and is producing winds at 4pi covering fractions, perhaps the sign of quasar feedback. |
| Vercellone | Long-term gamma-ray and multiwavelength observations of 3C 454.3 | S. Vercellone | During the period July 2007 - January 2009, the AGILE satellite and several other space and ground based observatories monitored the activity of the flat-spectrum radio quasar 3C 454.3, yielding the longest multiwavelength coverage of this gamma-ray quasar so far.
The source underwent an unprecedented period of very high activity above 100 MeV, a few time reaching gamma-ray flux levels on a day time scale higher than F=400E-8 ph/cm2/s, in conjunction with an extremely variable behavior in the optical R-band, even of the order of several tenth of magnitude in few hours, as shown by the WEBT-GASP light curves. We present the results of this long-term multiwavelength monitoring campaign, with particular emphasis on the study of possible lag between the different wavebands, and the results of the modeling of simultaneous spectral energy distributions at different levels of activity. |
| Vignali | Heavily obscured AGN in the local Universe: the Suzaku perspective | C. Vignali, A. Comastri, R. Gilli, K. Iwasawa, P. Ranalli, F. Fiore, G. Matt | Obscured AGN are routinely detected above 15 keV by INTEGRAL and Swift. As a consequence, the sample of Compton-thick AGN in the local Universe is growing, allowing us to make a more proper comparison with predictions by X-ray background synthesis models.
Here we present Suzaku broad-band spectra (up to 40 keV) of a sample of five obscured AGN detected either by INTEGRAL or Swift. All of them are heavily obscured (Nh>3e23 cm^-2), and three are Compton-thick; in two of them, the cold absorber almost fully covers the continuum source. Coupled with Suzaku archival observations, we find evidence of a wide range for the intensity of the reflected/scattered component, likely related to the geometry of the torus. Implications for the ongoing ultra-deep XMM-Newton survey in the Chandra Deep Field-South will be briefly discussed. |
| Villata | Last results from the GLAST-AGILE Support Program | M. Villata, C.M. Raiteri for the GASP Collaboration | The GLAST-AGILE Support Program (GASP) was born in 2007 to provide continuous optical-to-radio monitoring of 28 gamma-loud blazars for the coordinated study of their low- and high-energy emission.
We present the last achievements of the GASP during the gamma-ray flaring activity of some particular objects. |
| Vittorini | extreme energetics from the BL Lac S5 0716+714 | V. Vittorini & M. Tavani | BL Lac objects of the intermediate subclass (IBLs) emit most of their power in the energy range 100 MeV - 10 GeV.
Detecting gamma rays from such sources provides therefore a direct probe for their fundamental mechanism of emission and underlying power-house. The AGILE gamma-ray satellite detected the remarkable IBL S5 0716+714 (zsimeq 0.3) during the period September - October 2007, characterized by two very intense flares with fluxes reaching 200x10^{-8}ph / cm^2 sec. We present here a theoretical investigation of the main properties of this source, with particular emphasis on the flux and spectral variability. We model in detail these two flares, and study the overall energetics of the source. We conclude that 0716+714 is the most powerful BL Lac ever detected in gamma-ray. We find this source to be very close or even beyond the maximum energy extractable by the Blandford-Znajek mechanism from a rotating black hole of mass 10^9M_sun. |
| Volonteri | Evolution of black hole spins | Marta Volonteri | Black hole spins affect the efficiency of the "classical" accretion
processes, hence the radiative output from quasars. Spins also determine how much energy is extractable from the hole itself. Recently it became clear that massive black hole spins also affect the retention of MBHs in galaxy, because of the impulsive "gravitational recoil", up to thousands km/s, due to anisotropic emission of gravitational waves at merger. I will discuss the evolution of massive black hole spins along the cosmic history, due to the combination of MBH-MBH mergers and accretion events. I will also discuss the repercussions of spin evolution (alignment, spin-up, spin-down) onto the quasar and MBH populations. |
| Volpe | Overview of the recent AGN observations with H.E.S.S. | Francesca Volpe | The High Energy Stereoscopic System (HESS) has contributed with its sensitivity to the detection of distant blazars in the TeV range, providing us with an unprecedented view of the extragalactic sky at very high energies. With monitoring campaigns, H.E.S.S. has also searched for flux and spectral variability in blazars on timescales ranging from
months down to minutes. Recent results of the HESS observations of AGN will be here presented together with their physical implications. A particular emphasis will be given to the strong variability of PKS 2155-304 detected by HESS in July 2006, which for the first time in this energy domain resulted to be accounted for as a realization of a log-normal random stationary process. Finally, the results of the first joint observing campaign of PKS 2155-304 between HESS and FERMI LAT will be here presented, with the quantitative correlations between optical, X-rays, HE and VHE. |
| Wagner | Synoptic studies of 21 TeV blazars known today in very high-energy gamma-rays | Robert Wagner | Today we know that 27 active galactic nuclei (AGN) emit E>100 GeV gamma rays. The vast majority of them are blazars, while also some radio galaxies are now known to belong to the TeV AGNs. We compare the intrinsic TeV luminosities and spectral slopes of 21 TeV blazars in the E>100 GeV region and correlate them among each other, with X-ray, optical and radio data, and with the estimated black hole (BH) masses of the respective host galaxies. |
| Wagner | The relationship between optical synchrotron and GeV gamma-ray variability in Blazars | S. Wagner, B. Behera, M. Hauser | The high sensitivity and the continuous scanning operation of FGST
enable the compilation of continuous and well-sampled lightcurves. This in turn enables studies of the relationship between GeV gamma-ray and optical synchrotron variability which are less biassed by observational constraints. We have monitored GeV bright blazars at various wavelengths in the synchrotron domain. This paper discusses duty cycles and power spectra and compares the variations seen in the two energy bands. We derive constraints on the rate of those ejections in Blazar jets which are energetic enough to be detected in the GeV regime. |
| Wolter | |||
| Woo | Exploring the Disk-Jet Connection of Young Radio Galaxies Using NLR Properties | Jong-Hak Woo, Nozomu Kawakatu, & Tohru Nagao | We investigate whether the AGN jet formation is connected with specific accretion conditions by comparing the emission-line flux ratios of NLR. Using a sample of radio galaxies in the early stage of the jet activity, we find that young radio galaxies exhibit systematically larger flux ratios of [O I]6300/[O III]5007 and smaller flux ratios of [O III]5007/[O III]4363 than RQ Seyfert 2 galaxies. Compared with photoionization models, the difference in the flux ratios can be well understood by the difference in the SED of ionizing sources. Young radio galaxies favor SED without a strong big blue bump (BBB), i.e., a radiatively inefficient accretion flow (RIAF), while RQ AGNs are consistent with the models adopting SED with a strong BBB, i.e., a geometrically thin, optically thick disk. These findings imply that the formation of powerful AGN jets requires the accretion disk with harder ionizing SED (i.e., an RIAF). |
| Yuan | An MHD model for the formation of episodic jets | F. Yuan. J. Lin, K. Wu & L. Ho | Episodic ejection of plasma blobs have been observed
in many black hole systems. While steady, continuous jets are believed to be associated with large-scale open magnetic fields, what causes the episodic ejection of blobs remains unclear. Here by analogy with the coronal mass ejection on the Sun, we propose a magnetohydrodynamical model for episodic ejections from black holes associated with the closed magnetic fields in an accretion flow. Shear and turbulence of the accretion flow deform the field and result in the formation of a flux rope in the disk corona. Energy and helicity are accumulated and stored until a threshold is reached. The system then loses its equilibrium and the flux rope is thrust outward by the magnetic compression force in a catastrophic way. Our calculations show that for parameters appropriate for the black hole in our Galactic center, the plasmoid can attain relativistic speeds in about 35 minutes. |
| Zacharopoulou | Modification of blazar spectrum due to internal and extragalactic absorption | Zacharopoulou Olga, Khangulyan Dmitry, Aharonian Felix | Blazars are known TeV emitters. The gamma rays they produce are attenuated by the Extragalactic Background Light (EBL) through γγ absorption producing electron-positron pairs, γγ->e+e-. Using current models for the EBL we can deabsorbe the observed blazar spectrum. Following this, some of the deabsorbed spectra appear too hard. We introduce a model that can produce arbitrarily hard spectra. The key element in this procedure is internal absorption. We assume protons are accelerated to high energies by blobs in the relativistic outflow, subsequently emitting gamma rays via synchrotron radiation which are then absorbed by the radiation fields present in their production region (internal absorption). The electron-positron pairs that are created produce additional synchrotron radiation but at lower energies, forming the X-ray bump in the spectral energy distribution (SED). We will present the results of fitting the blazar's SED within the framework of this model. |
| Zensus | none | none | none |
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