The maximum poster size is 75 cm (width) x 120 cm (height). All posters will be displayed in the IPP building during the entire meeting. The poster boards will be assigned according to the numbers given in the abstract booklet. Moreover, two poster sessions of 30 minutes each are currently scheduled. During each session a group of poster rapporteurs will discuss their work with those interested in the Poster area.
Patricia Arevalo X-ray-optical variability of MCG-6-30-15
Abstract: We examine the temporal behaviour of the Seyfert 1 galaxy MCG--6-30-15 through observations made by XMM-Newton with a total time span of 450 ks. The simultaneous X-ray and U filter light curves produced show variabilities of 50% and 15% on short time scales, respectively. Cross correlating the light curves we find a strong and well defined peak indicating that the X-rays lag the U photons by ~ 160 ks while no features with negative time lags were found. We found a steepening in the spectrum of the 2-10keV continuum with increasing flux, which together with the positive correlation peak give support to the Comptonization scenario. The lack of features with a negative time lag reject models where the bulk of the U photons are produced through reprocessing of X-rays for this source, at least in time scales shorter than the observation. These results put constraints in the emission mechanisms of Seyfert galaxies and so, possibly, on the accretion onto a super-massive black hole
Bernd Aschenbach Measuring mass and angular momentum of black holes with high-frequency QPOs
Abstract: So far three galactic microquasars with high-frequency QPOs have been found each of which shows two frequencies which come in a 3:2 ratio. I have deloped a model which uses the Kepler frequency and both of the two epicyclic frequencies of a test particle orbiting a Kerr black hole to explain this ratio. The equations describing the model have exactly one solution, uniquely fixing the angular momentum of the black hole, which it has to have to start the oscillations, and the orbit radius where the oscillations are excited. I found exactly the same values for the angular momentum and the orbit radius by a detailed analysis of the Boyer-Lindquist functions which demonstrates that this angular momentum and this particular orbit radius are special, also from a physics point of view. The model is used to predict the mass of the three microquasars and the Sgr A* black hole using the QPO frequencies measured. The agreement between the predicted mass and the dynamically determined mass is very good for each of the four objects.
David Axon Measuring Black Hole Masses in Double Peaked Broad Lined AGN
Abstract: To date there have been few black hole (BH) mass estimates for luminous broad line AGN, including those derived from reverberation mapping. In this context, objects with "double-peaked" broad lines are particularly important because the line emission is believed to arise in a relativistically rotating accretion disk. If this model is correct, then the BH mass can be determined directly from periodic variations in the line-profile shape. In two cases (Arp 102B and NGC 1097) such variations have been claimed. We describe the first result from a HST STIS long-slit spectroscopy mapping of the velocity field of circum-nuclear ionized gas for 5 of the nearest and brightest "double-peaked emitters" (NGC 1097, Arp 102B, Pictor A, 3C390.3, 3C332), designed to set independent limits on the central masses of the systems .
Marcella Brusa Are QSO2 hiding among EROS?
Abstract: I present the results of a deep (about 80 ks) XMM-Newton survey of the largest sample of near-infrared selected Extremely Red Objects (R-K > 5) available to date (Daddi et al. 2000). At the relatively bright X-ray and near-infrared fluxes probed by the present observations, AGN account only for a negligible fraction (3%) of the ERO population; conversely, the fraction of EROs among X-ray selected samples is much higher (15-20%). The X-ray properties of EROs individually detected in the XMM-Newton observation indicate absorption in excess of 10^22 cm^-2. To place our findings in a broader context, we have also considered all the sources in the CDF-N sample (Barger et al. 2003) with ERO colors. Spectral analysis of the highest S/N sources unambiguously indicate that large column of cold gas (even > 10^23 cm^-2) are the rule rather than the exception. Although a spectroscopic redshift is not available for all of the sources, the X-ray, optical, and near-infrared properties of X-ray selected EROs nicely fit those expected for Quasars 2, the high-luminosity, high-redshift obscured AGNs predicted in XRB synthesis models.
Pieter Buyle Linking the black hole and bulge formation
Abstract: It has become established in recent years that most, if not all, galaxies harbor a Supermassive Black Hole (SBH) at their center. Moreover, the SBH mass is tighly connected to the large scale properties of the surrounding galaxy, in particular to the velocity dispersion (sigma) of the hot stellar component and, even more intruiging, to the total gravitational mass of the host (through the circular velocity v_c)(Ferrarese (2002), Baes et al. (2003)). Although this last relation is established for only 25 spiral galaxies, a clear trend is starting to emerge: the “v_c-sigma” relation seems to break down for low circular velocities reflecting a fundamental change in the modalities by which bulges form as the mass of the DM halo decreases below a critical value or indicating that the less massive halos are unable to form SBHs, as has been argued on theoretical grounds. To shed light on this problem we started a project to increase the amount of data, over a wide range of Hubble types and circular velocity amplitudes, and to model the dynamical motions of the stars in the vicinity of a SBH.
Max Camenzind The ISM of Ellipticals and Black Hole Evolution
Abstract: The interstellar matter (ISM) of elliptical bulges undergoes a dramatic evolution after the initial star burst. Gas is mainly injected by normal stellar evolution with an injection rate decreasing with time. Gas injection was about a factor 100 higher at redshift 3-5. Energy is injected mainly by SNe Ia and dissipation of kinetic stellar energy. These two facts forbid any hydrostatic solution for the ISM distribution and lead either to bulge winds or cooling flows. We discuss possible scenarios for the formation of dusty tori on the parsec--scale and their fuelling rates.
Francisco J. Carrera Why only high-redshift obscured AGN are bright submm sources?
Abstract: In our sample of matched X-ray absorbed and unabsorbed AGN, strong submm emission associated to star formation is found only in the high redshift X-ray absorbed sample, ruling out orientation effects as the cause of the absorption. These objects are probably undergoing a transition between a hidden growth phase and an unabsorbed AGN phase. SCUBA submm imaging reveals a ~400kpc long chain of galaxies around at least one of our AGN, and probably associated with it. These galaxies present strong obscured star formation, which could be associated with mergers or encounters within the filament.
Andrea Cattaneo Growing black holes in computer simulations of galaxy formation
Abstract: GalICS (Galaxies In Cosmological Simulations) is a semi-analytic model of galaxy formation that uses merger trees constructed from N-body simulations. AGNICS (Active Galactic Nuclei In Cosmological Simulations) is a new version of GalICS including the growth of supermassive black holes in galaxy nuclei. AGNICS starts from assuming that AGN are triggered by galaxy interaction/bars and models the contribution of AGN to the optical, sub-mm, radio and X-ray spectra of galaxies. It was developed to study the cosmic evolution of the quasar population and multiwavelength properties quasar hosts. However, it has also been used to investigate the role of black hole growth in relation to the overcooling problem affecting semi-analytic models of galaxy formation. In this talk I shall present the main results of the AGNICS model and their implications in relation to different scenarios for the growth of supermassive black holes. I shall place a special emphasis on the topics of optically unseen accretion, cold/hot gas accretion and AGN feedback.
Luca Ciotti A physically motivated toy model for the BH-spheroid coevolution
Abstract: We apply to a simple, yet physically motivated one-zone toy-model, the results presented by Sazonov et al. (this Conference). Our model describes over an Hubble time the coevolution of the central black hole and the galaxy stellar and gas content, under the influence of feedback due to the evolving stellar population and to the AGN activity induced by accretion. We show that, by adopting a duty cycle for the AGN activity as that derived from observations and from numerical simulations od feedback modulated accretion flows, the final Mbh/Mspheroid is in excellent agreement with the observations.
Lodovico Coccato Super Massive Black Holes masses in spiral galaxies. HST-STIS observations for 3 new objects
Abstract: We present long-slit HST-STIS measurements of the ionized gas kinematics in the nucleus of three spiral galaxies, namely NGC 2179, NGC 4343 and NGC 4435. The sample galaxies have been selected by means of ground based spectroscopy. Indeed, they are characterized by a strong central velocity gradient of ionized gas which is consistent with the presence of a SMBH. For each target galaxy we obtained the Ha and [NII] 6583 A kinematics along the major axis and two 0"25 offset position on the two sides of the nucleus. Out of three objects, only NGC 4435 turned out to have a ionized gas disk in regular motion. Preliminary modeling indicates a SMBH mass upper limit of 2e6 solar masses, which is definitely below the M-sigma relation for galaxies.
Stefano Cristiani Chemical abundances in quasar host galaxies from narrow absorption line systems
Abstract: We determined C, N and alpha-element relative abundances in the gas surrounding six quasars at an average redshift of < z > ~ 2.4, by studying six narrow associated absorption systems in UVES high-resolution spectra. We found five systems with a metallicity (measured by C/H) consistent or above the solar value. The average is
Jorge Cuadra Dynamical evolution of stars formed in accretion disks around super-massive black holes
Abstract: The standard accretion theory predicts that the outer parts (R $\ge 1000 R_{S}$) of QSO disks are self-gravitating and should form stars. Recent observations of our own Galactic Centre showed the presence of many young hot stars confined to two well defined rings of truly nuclear scale ( $<$ 0.1 pc). This lends support to theories of star formation in accretion disks, but also begs for an investigation of the star-disk system especially if the disk orientation changes with time. Using analytical estimates and numerical integration, we try to answer some of the basic questions here, such as whether the stars will be confined to the disk plane, whether the disk friction or the N-body effects will dominate the velocity dispersion and the formation of stellar groups, and what is the feedback of the stars on the disk temporal evolution.
Wolfgang Duschl The early formation of SMBHs in quasars
Abstract: We show that the rapid formation of super-massive black holes in quasars can indeed be understood in terms of major galaxy mergers followed by disk accretion. The necessary short disk evolution time can be achieved provided the disk viscosity is sufficiently large, which, for instance, is the case for hydrodynamic turbulence, unlimited by shock dissipation. We present numerical calculations for a representative case. This general picture can account for (a) the presence of highly luminous quasars at redshifts z > 6; (b) for the peak in quasar activity at z ~ 2; and (c) for a subsequent rapid disappearance of quasars at later epochs.
Andres Escala The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei.
Abstract: Andres Escala (1,2) Paolo Coppi & Richard Larson (1) Diego Mardones (2)
(1) Yale University. (2) Universidad de Chile.
Using high-resolution SPH numerical simulations, we investigate the effects of gas on the inspiral and merger of a massive black hole binary. This study is motivated by both observational and theoretical work that indicate the presence of large amounts of gas in the central regions of merging galaxies. N-body simulations have shown that the coalescence of a massive black hole binary eventually stalls in a stellar background. However, our simulations suggest that the massive black hole binary will finally merge if it is embedded in a gaseous background. Our work thus supports scenarios of massive black hole evolution and growth where hierarchical merging plays an important role. We also include preliminary results that estimates accretion rates in such dense gaseous environment. The final coalescence of the black holes leads to gravitational radiation emission that would be detectable up to high redshift by LISA.
Renato Falomo VLT adaptive optics observations of z ~ 2.5 quasars.
Abstract: R. Falomo(1), J. Kotilainen(2), A. Treves(3), Scarpa, R.(4)
(1) INAF- Osservatorio di Padova, Italy (2) Tuorla Observatory, University of Turku, Finland (3) Universita' dell'Insubria, Como, Italy (4) ESO, Chile
Abstract
We present K band images of distant quasars obtained with the adaptive optics system NAOS -- Conica at the VLT. The high resolution and deepness of the images allow us to investigate the properties of the environments of three quasars at redshift z=2.1 to 2.6, close to the peak of the cosmological evolution of QSO. These results are discussed in the context of the models of joint formation and evolution of alaxies and their active nuclei.
Elisa Ferrero XMM observations of four high-z quasars: PKS 2126-158, PKS 2149-306, Q 0000-263, Q 1442+2931
Abstract: Authors: E. Ferrero and W. Brinkmann
We present the results of XMM-Newton observations of four high-z quasars, two radio-loud and two radio-quiet. One of the radio-loud objects, PKS 2126-158, also classified as a Gigahertz-Peaked-Spectrum source, clearly shows absorption in excess of the galactic value as claimed before from ASCA and ROSAT observations. For PKS 2149-306 the evidence for excess absorption is only marginal in contrast to previous results. The location of the absorber in PKS 2126-158 is compatible with the redshift of the source. Both, a warm and a cold absorber are allowed by the X-ray data. Both quasars have very flat photon spectra (\Gamma \la 1.5) and the high photon statistics reveal small deviations from a simple power law form. For the two radio-quiet objects, Q 0000-263 and Q 1442+2931, we determine, for the first time, reliable spectral parameters. Both quasars have steeper power laws (\Gamma \sim 2) and show absorption consistent with the galactic value, similar to radio-quiet quasars at low redshifts. In the case of Q 0000-263 the presence of the damped Ly$\alpha $ system (N(HI)\sim 2.6\times 10^{21} cm^{-2} at z = 3.39) cannot be examined further due to the limited photon statistics in all instruments. An interesting connection between absorption in high-z quasars and Gigahertz-Peaked-Sources is suggested by the results for PKS 2126-158.
Giovanni Fossati Investigating the nature of relativistic jets by studying the demographics of Blazars
Abstract: We present an overview and selected results of our on-going FIRST Flat Spectrum Sample (FFSS) project. The goal of the FFSS is to shed light on the true nature and physical properties of radio-loud AGN jets, and in turn their relationship with the SMBH and accretion disk from which they are ultimately powered, through the understanding of the demographics of blazars. The FFSS is "designed" to give us a true(r) census of the different types of blazars, resolving a long-standing uncertainty, and the first step towards understanding how Nature makes jets. In order to do so, it is crucial to strive to select in an unprejudiced way all "flavors" of blazar (e.g. not distinguish a priori between BL Lac and FSRQ), and to be sensitive to both extrema of the SED "color" phenomenology. The FFSS is now 95% identified. It comprises ~600 objects, selected from the FIRST radio survey, representing a very diverse mix of FSRQ (currently 60%), BL Lacs (20%), and "galaxies" (15%), and it spans across the full range of SED colors, with relatively uniform statistics. We will discuss the modeling techniques that we are implementing, whose first goal is to test the current luminosity-color sequence paradigm, and to discriminate among competing unification schemes.
Stephan Frank A New Approach to Characterizing the SEDs of AGNs from Deep Multi-Wavelength Observations
Abstract: We use data from the CDFN 2 Ms survey and related multi-wavelength observations to investigate the nature of the intrinsic SEDs of AGNs, how they may vary with redshift and luminosity, and how the data may be affected by obscuration and possible contributions from starbursts. Our goal is to find a simple, effective way to use multi-wavelength data to characterize the intrinsic SEDs of AGNs. We believe that shifting the observational data to the emitted frame of the AGN provides a direct way to visualize the effects of obscuration and possible changes in the underlying SED from object to object. This will assist our understanding of the evolution of AGNs and their contribution to the X-ray background. For the 270 point sources in the CDFN catalogue with spectroscopically known redshifts, we transformed the observed flux in each available wavelength band to the emitted flux at the source. In order to characterize the X-ray data we used the published values of gamma_effective. Plots of the SEDs in the emitted frame provide a very useful tool for visualizing effects such as the variation of X-ray slopes and changes in the optical to X-ray flux ratios as a function of redshift and luminosity. For example, we investigate 1) how the Elvis et al. reference SED for low-redshift AGNs compares with the new data, which span a much larger range of redshift and luminosity, 2) how a newly defined alpha_OX based on 2500AA and 8keV fluxes may be a better indicator of the intrinsic properties of AGNs than the traditional one, and 3) what our approach tells us about the nature of low-luminosity AGNs and the contribution of starbursts to the observed multi-wavelength SEDs.
Isabelle Gavignaud The VIRMOS VLT Deep Survey QSO sample
Abstract: The VIMOS-VLT Deep Survey is a purely flux limited spectroscopic survey, free of color or morphological biases. It's limiting magnitudes are I_AB=24.0 in the deep area (1.2 square deg), and I_AB=22.5 in the wide area (16 square deg). Among the ~20000 spectroscopic observations already performed, we have compiled a preliminary catalogue of 85 broad lines AGN up to redshift 5. We present here the properties of this sample.
Jose L. Gomez The jet in the radio galaxy 3C120 and its connection with the accretion disk and SMBH
Abstract: By Gomez, J. L., Marscher, A. P., Jorstad, S. G., & Agudo, I.
Intensive multi-frequency polarimetric VLBA and X-ray monitoring observations of the radio galaxy 3C120 will be presented, providing further information on the nature of the radio jet and its connection with the accretion disk and SMBH. The VLBA data provides detailed information on the jet dynamics, structure of the magnetic field, and interaction with the external medium at the inner parsec scales. Superluminal components are observed to appear after the observation of dips in the X-ray light curves, suggesting that part of the inner accretion disk that is not swallowed by the SMBH is used to feed the relativistic jets.
Hans-Jakob Grimm X-ray variability of the Milky Way
Abstract: By constructing the power density spectrum of the Milky Way due to Galactic X-ray binaries we investigate the prospect of disentangling the X-ray emission of galaxies due to SMBHs and X-ray binary populations for future X-ray missions.
Dirk Grupe The growing black holes in Narrow-Line Seyfert 1 galaxies
Abstract: One of the most fundamental relations found among nearby galaxies and AGN is the M-sigma relation between the black hole mass and the bulge stellar velocity dispersion. However, Narrow-Line Seyfert 1 galaxies (NLS1s) seem to deviate from this relation. I will show in my talk that the reason for this deviation is that NLS1s are AGN in a young state of their development and their black hole mass is still evolving.
Ryan Houghton Supermassive black hole masses in the local universe with adaptive optics
Abstract: We report the first results from our program to measure the masses of supermassive black holes in the local universe, using the ESO VLT and adaptive optics. The study seeks to complement results obtained with HST by extending the sample, both at the high mass, low surface brightness end (cores of giant ellipticals) and at in lower mass, extincted spiral nuclei. We will present first results from recent observations made with NAOS/CONICA at near-IR wavelengths of the nucleus of NGC 1399 (Fornax A) and two other galaxies.
Valentin Ivanov Black Hole Masses in SDSS QSOs
Abstract: TBD
Agnieszka Janiuk What triggers the activity cycle in galactic nuclei?
Abstract: We present a theoretical study of a time evolution of an accretion disk around a supermassive black hole. In a certain range of temperatures, the disk may be subject to the hydrogen ionization instability. This causes an on-off activity cycle, which amplitude is substantially high if either the efficiency of angular momentum transport varies between the active and quiescent phases, or if the innermost disk temporarily evaporates and forms radiatively inefficient ADAF. We demonstrate, that the second possibility is more suitable, since the strength of MHD turbulence implies that the viscosity parameter is constant throughout the whole instability cycle.
Sebastian Jester A simple test for the existence of two accretion modes in AGN
Abstract: By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion flow. If the radiative efficiency changes at some critical accretion rate, there will be a change in the distribution of black hole masses and bolometric luminosities at the corresponding transition luminosity. To test this prediction, I consider the joint distribution of AGN black hole masses and bolometric luminosities for a sample taken from the literature. The small number of objects with low Eddington-scaled accretion rates mdot < 0.01 and black hole masses Mbh < 10^9 Msun constitutes tentative evidence for the existence of such a transition in AGN. Selection effects, in particular those associated with flux-limited samples, systematically exclude objects in particular regions of the Luminosity-Black hole mass plane. Therefore, they require particular attention in the analysis of distributions of black hole mass, bolometric luminosity, and derived quantities like the accretion rate. I suggest further observational tests of the BHXB-AGN unification scheme which are based on the jet domination of the energy output of BHXBs in the hard state, and on the possible equivalence of BHXB in the very high (or steep power-law) state showing ejections and efficiently accreting quasars and radio galaxies with powerful radio jets.
Bruno Jungwiert Feeding the central kiloparsec by long-term stellar mass-loss
Abstract: Stellar mass-loss by low-mass stars is an important mechanism to refuel galactic disks and bulges by gaz over the Hubble time. Using analytical and N-body models with non-instantaneous gas recycling, we show how stellar mass-loss from both disk and bulge stars affects the fuelling, concentration and dynamics of the central kiloparsec. We discuss how the gas return rate from stars compares with large-scale inflow due to bars.
Toshihiro Kawaguchi Growth of massive black holes by super-Eddington accretion
Abstract: We discuss a couple of Narrow-Line Seyfert 1 galaxies whose accretion rate, in the unit of Eddington accretion rate, seem to be the highest (Mdot sim 1000 L_Edd/c^2) among Active Galactic Nuclei (AGNs). Theoretical arguments in (broad-band) spectral modeling will be presented. Then, based on the average accretion rate and the duration of super-Eddington AGNs, we discuss to what extent massive black holes grow via super-Eddington accretion, and compare it with the growth in sub-Eddington accretion regime.
Nozomu Kawakatsu The Growth of SMBHs in Optically-Thick Starburst Galaxies
Abstract: The formation and growth of supermassive balck holes (SMBHs)linked with bulges are considered. We focus on the radiation hydrodynamic process for the growth of SMBH in the optically thick starburst phase (e.g.,ULIRG), where radiation from bulge stars drives the mass accretion on to a galactic center from a galactic scale through radiation drag (Poynting-Robertson)effect. In this scenario, we found that SMBH-to-bulge mass ratio is basically determined by the nuclear energy conversion efficiency from hydrogen to helium, \epsilon=0.007.Furthermore, we have constructed the coevolution model of AGN (accreting BH) and host galaxy. First, we have made this model apply to QSO hosts (ellipticals). As a result, it is found that the AGN luminosity-dominant phase (QSO phase) is preceded by the host luminosity-dominant phase, which is called "proto-QSO phase". This phase corresponds to the early phase with broad emission line width of less than 1500km/s, and can be regarded as a "Narrow line Type I QSO (NLQSO1)". Also, its hosts have massive dusty disks within youger bulges. In addition, it is anticipated by an optically-thick starburst phase (ULIRG). In this phase, the BH mass fraction is predicted to be even less than 0.002.Second, such radiation drag model has been also applied to disk galaxies. As a consequence, we found that the SMBH should be smaller in a disk galaxy, but correlate with the bulge components. Thus, by analogy to proto-QSOs, NLS1s (BH growing phase) may have massive dusty disks within younger bulges. Therefore, the preset model could be a physical picture of evolution of LIRGs(ULIRGs) to Sys (QSOs);LIRGs(ULIRGs)-> NLS1s(NLQSOs)->Sy1s(QSO1s)->LLAGN. Finally, we discuss a possible candidate for NLQSOs by considering theoretical predictions for the observable properties.
Wolfram Kollatschny SMBH Mass derived from 2D-Reverberation and Gravitational Redshift Measurements
Abstract: Reverberation mapping of variable line intensities in AGN gives us information on the size of the broad line emitting region. The combination of the size with the internal velocity of the line emitting region (line width) allows us to estimate the central black hole mass in AGN.
The 2D-Reverberation mapping method of the variable line profiles yields the geometry and velocity gradient in the BLR more accurately. We present results of a spectral variability campaign of Mrk110 carried out with the 9.2m HET telescope at McDonald Observatory. The additional detection of a gravitational redshift effect in the optical emission line profiles gives us an independently derived value of the central black hole mass. The mutual comparison of these two black hole mass estimates allows us to derive the inclination angle of the central disk and therefore of the spin orientation of the black hole.
Bifang Liu Accretion in the Galactic Center: via cool disk?
Abstract: We study the possibility of a cool disk existing in the Galactic Center in the framework of the disk-corona evaporation/condensation model. Assuming an inactive disk, a hot corona should form above the disk since there is a continuous supply of hot gas from stellar winds of the close-by massive stars. Whether the cool disk can survive depends on the mass exchange between the disk and corona. If the disk-corona interaction is dominated by evaporation and the rate is larger than the Bondi accretion rate in the Galactic Center, the disk will be depleted within a certain time period and no persistent disk will exist. On the other hand, if the interaction results in hot gas steadily condensing into the disk, an inactive cool disk might survive. For this case we further investigate the Bremsstrahlung radiation from the hot corona and compare it with the observed X-ray luminosity. Our model shows that, for standard viscosity in the corona(alpha=0.3), the mass evaporation rate is much higher than the Bondi accretion rate and the coronal density is much larger than that inferred from Chandra observations. An inactive disk can not survive such strong evaporation. For small viscosity (alpha<0.07) we find condensation solutions. But detailed computations show that in this case there is too much X-ray radiation from the corona to be in agreement with the observations. Therefore, we conclude that there should be no thin/inactive disk presently in the Galactic Center. However, we do not exclude that the alternative non-radiative model of Nayakshin & Sunyaev (2004) might instead be realized in nature.
Andrei Lobanov Mergers and binary systems of SMBH in contexts of nuclear activity and galaxy evolution
Abstract: Galaxy evolution and nuclear activity in galaxies can be connected with the cosmological evolution of super-massive black holes (SMBH) in the galactic nuclei. Galaxies are expected to merge frequently over the course of their formation and cosmological evolution, leading to the the formation of binary systems of SMBH. Binary SMBH are likely to play a crucial role in formation and evolution of active galactic nuclei (AGN). The dynamic evolution of a binary SMBH may be a key factor affecting a large fraction of the observed properties of AGN and galaxy evolution. In this framework, different classes of AGN can be related in general to 4 different evolutionary stages in a binary SMBH: 1) early merger stage; 2) wide pair stage; 3) close pair stage; and 4) coalescence stage. This scheme will be described in the contribution, in connection with a variety of observational properties that can be explained by the binary SMBH scenario: radio and optical luminosity variations between different classes of AGN, long-term and short-term variability, quasi-periodic nuclear flares, and recurrent formation of relativistic outflows in AGN and their apparent morphology and kinematics.
Mami Machida Global Three-dimensional MHD Simulations of Co-existence of Hard State and Soft State Disks in Black Holes
Abstract: We present the results of three-dimensional global resistive magnetohydrodynamic (MHD) simulations of black hole accretion flows. General relativistic effects are simulated by using the pseudo-Newtonian potential. The initial state is an equilibrium model of a torus threaded by weak toroidal magnetic field. As the magneto-rotational instability (MRI) grows in the torus, mass accretes to the black hole by losing the angular momentum.
When the mass accretion rate is small enough, the disk stays in an ADAF blanch at all radius.As the mass accretion rate increases, ADAF blanch disappears outside some critical radius, above which the disk makes transition to an optically thisk, cold state. Hard-state disks in the inner region co-exists with soft-state disks in the outer region.
Vincenzo Mainieri Beyond the spectroscopic limit in the GOODS/CDFS survey
Abstract: We present a detailed study of the X-ray/optical/near-IR properties and redshift distribution of the X-ray sources in the Chandra Deep Field South Survey with optical counterparts fainter than R> 25. These magnitudes are beyond the spectroscopic limit also for 10 m ground based optical telescopes. Optically faint sources represent ~25% of the whole X-ray population in the CDF-S. We use the unique multi-wavelength follow up of the GOODS survey and the recently released UDF data. Adding the derived photometric redshifts for these faint sources in the redshift distribution we are able to attenuate the disagreement with the prediction of synthesis models of the X-ray Background but not to solve it. Therefore it is mandatory to include in synthesis models a new X-ray luminosity function of unobscured AGN. The Optically faint sources are mainly X-ray absorbed AGN ( ~83% have NH>10^22 cm-2). Many of these faint sources have high (>10) X-ray-to-optical flux ratios and we find that half of them are well fitted with a SED of an elliptical galaxy with
Rowena Malbon Quasars in Hierarchical Galaxy Formation
Abstract: Observations suggest a fundamental relationship between black holes and their host galactic bulges. Quasars are often associated with violent starbursts and galaxy mergers, which may also trigger bulge formation. We add black holes and quasars to a hierarchical galaxy formation model, to study the growth of supermassive black holes by mergers and accretion.
Dan Maoz An HST UV variability survey of LINERs: How quietly do dormant black holes sleep?
Abstract: A prerequisite to understanding the accretion mode of low-level-activity black holes such as LINERs is to isolate the direct emission from the accretion disk, from other sources, e.g., stars (in the optical/UV) and jets (in the radio). This is especially critical in LINERs, which constitute the most common AGNs, and which exist in the majority of massive bulges. I will present new results from a just-completed UV monitoring program carried out with HST on 17 LINER nuclei, aimed at quantifying the relative contribution to the UV emission of stars vs. nonstellar processes. This is important not only for deriving the true SED of dormant black hole emission, but also for understanding to what degree LINERs are signposts of the existence of an MBH -- a LINER spectrum is largely the result of photoionization by UV photons, yet is in not clear whether those photons come from an AGN or from massive stars.
Herman Marshall A Chandra Survey of Quasar Jets
Abstract: We present results from Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like extended structure. Over half of 30 quasar jets are detected in short exposures. The quasars without X-ray jets are not significantly different from those with detected jets except that the extended radio emission is generally somewhat fainter. New radio maps are combined with the X-ray images in order to elucidate the relation between radio and X-ray emission in spatially resolved structures. We find a variety of morphologies. The FR II X-ray jets can generally be interpreted as inverse Compton scattering of cosmic microwave background photons by electrons in large-scale relativistic jets aligned at an average of 20 degrees to the line of sight. This work was supported under NASA contract SAO SV1-61010 for the Chandra Science Center.
Emmi Meyer-Hofmeister A disk in the Galactic Center in the past?
Abstract: Authors: E. Meyer-Hofmeister, F. Meyer, B.F. Liu We raise the question whether in the past a disk could have existed in our Galactic Center which has disappeared now. Our model for the interaction of a cool disk and a hot corona above (Liu, Meyer, Meyer-Hofmeister 2004) allows to estimate an upper limit for the mass that might have been left over in a putative accretion disk after a last star forming event, but would now have evaporated by coronal action. The evaporation rate derived in our analysis depends on the value of the viscosity parameter assumed. For a standard value alpha =0.3 and no wind escape from the corona we found a rate of 10^-2.9 times the Eddington accretion rate corresponding to 10^-4 solar masses per year. The evaporation rate is higher than the rate of gas accreting now deduced from Chandra observations of the hot X-ray emitting thermal gas in the vicinity of the Bondi accretion radius. We consider the history of our Galactic Center during the lifetime of the stars observed close to the Galactic Center. The observations, and especially spectroscopy of one such star, S0-2, suggest that these are main sequence O/B stars (Eisenhauer et al. 2003, Ghez et al. 2003). The O/B stars could have formed not longer ago than their main sequence lifetime, of order of 10^6.5-10^7 years (Maeder \& Meynet 1989). If we assume that, as suggested by the observations, now no disk exists, it follows the gas that remained in a disk after these stars had been formed should have been less than 300 to 1000 solar masses. This value is in the range of mass of the presently observed bright O/B stars close to the Galactic Center. Such an estimate would also be of interest in the framework of star formation in the Galactic Center as recently discussed by Milosavljevic and Loeb (astro-ph 0401221). Interestingly, but, perhaps fortuitously, this amount of gas is also close to that of the stability limit of a disk against self-gravitation. This suggests as a possible picture for the evolutionary history that a disk could have become unstable by self-gravitation and formed the presently observed young massive stars around the Galactic Center until the gravitational instability had ceased. The remaining gas would have evaporated by now.
Friedrich Meyer Super-Eddington luminosity from fragmentated accretion disks
Abstract: Ultraluminous X-ray sources (ULXs) with observed luminosities of $10^{39.5}$ to $10^{41}$erg/s and spectra fitted by multi-temperature black body radiation of temperatures 1-2 keV are thought to be black holes accreting mass from a late O type stellar companion at high rate. In order not to exceed the Eddington limit the accreting black holes would have to be of intermediate mass, 50-100 $M_\odot$, while the observed disk temperatures are too high for such black hole masses (Makishima et al. 2000). Various suggestions have been made to resolve this problem. We suggest a new instability in disk/corona systems which leads to fragmentation of accretion disks in strong magnetic fields under radiation pressure and allows Super-Eddington radiation from the fragmented accretion disk. The essential physics is the following. Radiation pressure supported disks in magnetic fields are unstable against a ``photon- bubble instability''. In a non-linear version such radiation driven inhomogeneities can allow the escaping flux to exceed the Eddington limit and were suggested as resolution of the ULX problem (Begelman 2000, 2002). We here propose that radiation pressure leads to a complete fragmentation of accretion disks in magnetic fields around black holes and that radiation escapes through the gaps between fragments at super-Eddington luminosity. Essential for the gap formation is the overlying disk corona into which gas of too low a density evaporates.
Takamitsu Miyaji X-ray Sources in the Groth-Westphal Field and the Eddington Ratio
Abstract: We discuss the multiwavelength nature of the X-ray sources detected in the 80 ks XMM-Newton observations in the Groth-Westphal region. Typical sources have Log Lx [erg/s]~44 and z~1, which mark the peak of the accretion onto supermassive blackholes. We discuss our infrared spectroscopy of H-alpha+[NII], host galaxy colors and estimated Eddington ratio of these sources.
Monika Moscibrodzka A model of accretion flow onto Sgr A*
Abstract: We consider an accretion flow onto the black hole in Sgr A*. We assume that most of the material is provided by the wind from IRS 13E1, and that the black hole is surrounded by a cold passive disk (Nayakshin, Cuadra and Sunyaev 2003). The flow above and just below the spherical Bondi radius is described using a semi-analytical solution of Beskin (1995), the inner flow is represented in the ballistic approximation. We determine the fraction of the mass accretion flow reaching the black hole directly and we analyse the radial distribution of the mass settling onto the disk. We discuss the observational consequences of the model.
Nelly Mouawad Weighing the cusp at the Galactic Centre
Abstract: As stars close to the galactic centre have short orbital periods it has been possible to trace large fractions of their orbits in recent years. Previously the data of the orbit of the star S2 have been fitted with Keplerian orbits corresponding to a 3-4*10^6 Msun massive black hole (MBH). However, it has also been shown that the central black hole resides in a ~1'' diameter stellar cluster of a priori unknown mass. In a spherical potential which is neither Keplerian nor harmonic, orbits will precess resulting in rosetta shaped trajectories on the sky. In this case, the assumption of non-Keplerian orbits is a more physical approach. It is also the only approach through which cusp mass information can be obtained via stellar dynamics of the cusp members. This work presents the first exemplary modelling efforts in this direction. In addition to the solution of a 3.7*10^6 Msun black hole with insignificant cusp mass, we obtain best fits for a total (MBH plus cusp) mass of 4.1*10^6 Msun with 10% extended component and 4.8*10^6 Msun total mass with a 25% extended component. While high total masses above ~5*10^6 Msun are in conflict with enclosed mass estimates at larger radii, there is no contradiction for the 10% cusp mass solution which is discussed in detail. It is unlikely that such a high extended mass is composed of sub-solar mass constituents, but could be explained rather well by a cluster of high M/L stellar remnants, which we find to form a stable configuration.
Alain Omont Redshifted far-infrared/submm dust and CO emission from high z QSOs
Abstract: The results of several years of IRAM-30m/MAMBO observations at 1.2mm of dust emission of bright QSOs at z ~ 2-6 will be summarised and discussed, as well as subsequent CO detections with the IRAM interferometer: dust detection in more than 55 sources, and CO in eight of them; dependence of the far-IR luminosity with redshift and bolometric luminosity; molecular gas properties; lensing; etc., with emphasis on prominent sources at z > 6 and others. Properties of the central kiloparsec of the host galaxies will be inferred, including: dust temperature and mass, origin of dust heating; H2 and virial masses; evidence for starburst and star formation rate. Implications for the black-hole growth will be discussed.
Mikhail Revnivtsev Statistical properties of local AGNs inferred from the RXTE 3-20 keV all-sky survey
Abstract: We performed all sky survey at energies 3-20 keV with the RXTE/PCA. Out of 294 detected sources 100 sources were identified with AGNs. We use them to study the statistical properties of the local population of AGNs. We find that among low X-ray luminosity (Lx < 10^43.5 erg/s) AGNs, the ratio of absorbed (characterized by intrinsic absorption in the range 10^22 cm^-2 < NH < 10^24 cm^-2) and unabsorbed (NH < 10^22 cm^-2) objects is 2:1, while this ratio drops to less than 1:5 for higher luminosity AGNs. This dramatic change may be physically related to an observed steepening of the 3-20 keV AGN luminosity function above Lx ~ 10^43.5 erg/s. The summed X-ray output of AGNs with Lx > 10^41 erg/s estimated here is smaller than the earlier estimated total X-ray volume emissivity in the local Universe, suggesting that a comparable X-ray flux may be produced together by lower luminosity AGNs, non-active galaxies and clusters of galaxies
Brigitte Rocca-Volmerange Radio Galaxies of 10**12 Msol at z > 4
Abstract: The link between the most massive galaxies and high-z super massive black holes is found from the K-z relation of radio sources all along the 0
Eduardo Rubio Herrera Stability and Oscillations on Thick Accretion Discs (Tori)
Abstract: We present a numerical study of the response of a Thick Accretion Disk (Torus) against radial, periodic perturbations with the aim of exciting internal modes which may produce resonances or beating phenomena. We have investigated this by using constant and non-constant angular momentum distributions within the disk. Our models are scale-free and can be used to simulate accretion tori around stellar or supermassive black holes.
Mara Salvato Multiwavelength scaling relations for nuclei of Seyfert galaxies
Abstract: We analyze an X-ray flux-limited, complete sample of 93 AGN at z$< $0.1, selected from the ROSAT Bright Survey. Two thirds of the sample are Seyfert 1 galaxies (Sy1) and one third are Narrow-Line Seyfert 1 galaxies (NLSy1). We have obtained optical images of all objects. By modeling the host galaxy and the AGN central component we decompose the optical emission into nuclear, bulge and disk components, respectively. We find that the nuclear optical luminosity, thought to be associated with the accretion disk surrounding the active black hole, correlates with the X-ray luminosity, the radio luminosity and the black hole mass.
Rainer Schoedel The compact stellar cluster around Sagittarius A*
Abstract: The stellar cluster around Sagittarius A* provides unique information on stellar distribution and dynamics near the supermassive black hole in a quiescent galaxy nucleus. Consistent with theoretical expectations, a density cusp of stars is found centred on Sgr~A*. Individual stellar orbits as well as measurements of the velocity dispersion of stars as close as 20 mpc from the black hole allow to examine the isotropy of the stellar cusp around the ~3.5 million solar mass black hole. We also present proper motion data on the IRS 13 cluster which has been suspected of being the remains of a dissolved cluster.
Alberto Sesana Low-frequency gravitational radiation from coalescing massive black hole binaries in hierarchical cosmologies
Abstract: We compute the expected gravitational wave signal from coalescing massive black hole (MBH) binaries at the center of galaxies in a hierarchical structure formation scenario in which seed holes of intermediate mass form far up in the dark halo merger tree. The merger history of DM halos and MBHs is followed from z=20 to the present in a LCDM cosmology. MBHs get incorporated through halo mergers into larger and larger structures, sink to the center owing to dynamical friction against the DM background, accrete cold material in the merger remnant, and form MBH binary systems. Stellar dynamical interactions cause the hardening of the binary at large separations, while gravitational wave emission takes over at small radii and leads to the final coalescence of the pair. The integrated emission from inspiraling MBH binaries results in a gravitational wave background (GWB). The characteristic strain spectrum has the standard h_c(f)\propto f^{-2/3} behavior only in the range 1E-9
Francesco Shankar SMBH Demography and limits on the AGN visibility timescales
Abstract: We have pursued a very detailed analysis of the local SMBH mass function through kinematical and photometric data. We show that the total mass density amounts to (4.2+-1.1)*10^5 M_sun/Mpc^3, out of which about 25% is the contribution from SMBH residing in late type bulges. Exploiting the recent available AGN Hard X-ray LF, we have studied the accretion history of the SMBH population. We have linked the SMBH mass and AGN luminosity through an exponential light curve and found that, with a non-constant Eddington ratio, a very good fit to the local SMBH mass function can be provided, as long as the ratio K_bol/eta is kept ~ constant with eta ~ 10%. Moreover, properly developing the mass continuity equation, we have been able to set more stringent limits on the fundamental parameters regulating accretion. In particular comparing the numerical estimates for the relic and active SMBH populations we find eta=(0.06-0.13) and L/Ledd=(0.6-1.3), assuming a 30% uncertainty on the bolometric correction and tau visibility greater than 4*10^7 yr .
Aneta Siemiginowska Intermittency, Accretion Disks and AGN evolution
Abstract: Accretion onto a supermassive black hole (SMBH) is generally accepted as the basis of AGN activity, however there are still many questions about properties of the accretion flow as well as the fuel supply to the innermost regions of the host galaxy. There is growing evidence that the AGN activity could be intermittent. Is the source of the intermittency related to the large scale physics (mergers, feedback etc) or there is some intrinsic property of the accretion flow that induces such behaviour? Here we present theoretical discussion and supporting observational evidence for intermittent activity and the corresponding timescales. We discuss these timescales in the context of the characteristic timescales of accretion disk instabilities. Finally we link evolution of the accretion disk to different states of AGN activity. This evolution scenario is decoupled from any external fuel supply, although it requires a continuous fuel supply into the accretion disk.
Lukasz Stawarz Multiwavelength Emission of Large-Scale Quasar Jets
Abstract: AUTHORS: L. Stawarz, M. Sikora, M. Ostrowski & M.C. Begelman.
We discuss morphological and spectral properties of the large-scale jets in powerful radio sources, which are now observed at radio, optical and X-ray frequencies. We propose, that the knots of such jets represent moving and separate portions of the jet matter, with the excess kinetic power. We suggest a possible connection between this scenario and the idea of intermittent/highly modulated jet activity. The proposed model can explain some morphological properties of quasar jets -- like high knot-to-interknot brightness contrasts, frequency-independent knot profiles and almost universal extents of the knot regions -- independently of the exact emission mechanism responsible for producing the X-rays, which is still under debate.
Ladislav Subr Nuclear star cluster in galaxies - interaction with an embedded accretion disc
Abstract: We explore structure of a stellar cluster whose dynamics is dominated by gravity of the central mass and interactions of individual stars with an accretion disc. We show that the cluster properties are determined predominantly by the radial profile of the disc characteristics (column density, thickness, viscosity). Rates of the star flow towards the centre are also given within simple steady-state model.
Aldo Treves Optical Spectroscopy of BL Lac objects with the ESO VLT+FORS1
Abstract: B. Sbarufatti, R. Falomo, J. Heidt, J. Kotilainen, R. Scarpa, A. Treves.
Spectra of BL Lac objects exhibit no or very weak spectral lines. On the other hand their host galaxies are known to be massive ellipticals, the spectrum of which is characterized by a number of well known absorption lines. The possibility of detecting such lines depends on the ratio between the nucleus and the galaxy luminosity and on the redshift. In some cases faint emission lines from the nucleus are also expected. We present here high S/N optical spectra of 32 objects of unknown redshift, obtained with ESO VLT+FORS1 and aimed to detect such lines. These new spectra allow us to derive the redshift in a number of sources but some other spectra, for rather bright (V<16,S/N>300$) objects, still remain lineless. These are either luminous high z sources or intermediate redshift objects with sub-luminous hosts.
Sachiko Tsuruta Shocks in the Black Hole Magnetosphere of Accretion-Powered AGN
Abstract: Previous work on winds from black hole magnetosphere in connection with rotation-powered AGN is extended to MHD accretion flows onto a supermassive black hole in the magnetosphere of an accretion-powered AGN. Fully general relativistic treatment is applied. Shock formation in such accretion flows is investigated. The results will be reported. Possible observational implication will be discussed.
Tanya Urrutia Optical red quasars are X-ray blue quasars
Abstract: Using a combination of the 2MASS near-infrared survey, the FIRST radio survey and the APM scans of the Palomar Sky Survey plates, we have selected a sample of 12 dust-reddened quasars with 0.4 $<$ z $<$ 3 and rest-frame reddenings in the range 0.4 $<$ E(B-V) $<$ 1.7. We obtained ACIS-S observations of these quasars and estimated the column densities towards them, and hence obtained the gas:dust ratios in the material obscuring the quasar. We detect all but one of the red quasars in the X-rays. All of the sources show absorbed X-ray spectra and the faintest sources are also the hardest (bluest) in the X-rays, arguing for high column density absorption. When we correct the luminosity absorption, they can be placed among the highest luminosity quasars, therefore our objects seem to be the high luminosity analogues of the sources contributing to the X-ray background seen in deep X-ray observations. We investigate the number density of these sources based on the X-ray background and give estimates to find more moderate luminosity red quasars with X-ray data.
Jian-Min Wang A possible feature of thermal matter in relativistic jet of radio-loud quasar
Abstract: It has been suggested that relativistic jets in quasars may contain a considerable amount of thermal matter. In this paper, we explore the possibility that the K\alpha line from the thermal matter may appear at tens of keV due to a high Doppler blue-shift. In the jet comoving frame, the energy density of photons originally emitted by the accretion disk and reflected off the broad line region clouds dominates over that of photons of other origin. We discuss the photoionization states of the thermal matter and find that the irons elements are neutral. The high metallicity in quasars enhances the possibility to detect the thermal matter in the relativistic jet in some radio-loud quasars. A highly Doppler blue-shifted K\alpha line may be detected. We make a prediction for 3C 273, in which the K\alpha line luminosity might be of the order 3.0 \times 10^{44} erg/s with an equivalent width of 2.4 keV. Such a line could be detected in a future mission.
Yiping Wang X-ray viewing the cosmic star formation history
Abstract: Based on our previous work about a co-evolution scheme of the central massive black holes and their host spheroids, we use the observed X-ray luminosity function of AGNs and their evolution rate by ROSAT to estimate the cosmic star formation history which is associated with AGN accretion. We show: 1) the total amount of star formation associated with massive black hole growth is at least half of the net star formation in the early Universe, which probably totally missed by our current UV/optical deep surveys; 2) the far-infrared emission from the dust heated by star formation on-going during the black hole growth could sufficiently account for the observed SCUBA counts, would the possible candidates of the SCUBA population; 3) the peak redshift of those massive spheroid formation seems to be in a redshift range of 1.5-2, not necessary to be at much higher redshift.
Margrethe Wold The influence of black hole mass and accretion rate on the FRI/FRII radio galaxy dichotomy
Abstract: The cause of the FRI/FRII radio galaxy dichotomy is opaque; it is unclear whether the differences between the two types are caused by fundamental properties of their 'central engines', or by differences in the central kpc-scale gaseous environment of the host galaxies. Using a sample of 20 FRI and FRII galaxies at z<0.2, we are therefore investigating the influence of black hole mass and accretion rate on the FRI/FRII dichotomy. We use the well-known M-sigma relation to estimate black hole masses by measuring the central stellar velocity dispersions from medium-resolution optical spectra. The spectra are centered on the MgIb and the CaH&K absorption line systems, and we use the direct template-fitting method of Barth, Ho \& Sargent (2002) which allows us to exclude regions of the spectra around strong emission lines. The black hole accretion rate is calculated from the narrow emission-line luminosity, assuming that it scales with the photoionizing luminosity of the central AGN. For several of the galaxies in our sample, we have used narrow emission line luminosities from the literature, but for some which can not be found in the literature, new data have been obtained.
Weimin Yuan Large-amplitude X-ray variability in the LLAGN NGC7589:
Abstract: Accretion onto supermassive black holes is suggested to take distinct forms, standard thin accretion disc and radiatively inefficient accretion flow. The accretion rate determines the mode. A possible test of this hypothesis comes from observations of objects undergoing a large variation in the accretion rate which cross the `critical rate' where the transition of accretion mode occurs. We report here a detection of a large amplitude X-ray variability in the galaxy NGC7589. If the variability is intrinsic to the radiated power, the inferred mass accretion rate increased from much `sub-critical' to values comparable to the critical rate. We present X-ray and optical observations of NGC7589, which was found to be a Seyfert--LINER transition galaxy. The galaxy provides a good candidate for future intensive monitoring.