This contribution reviews two topics of current interest in the study of black hole demographics in active galaxies: Can the stellar velocity dispersions of quasar host galaxies be measured? And can we constrain the black hole mass function below 106 M$_\odot$?To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have embarked in an HST program to determine the masses of black holes in spiral galaxies directly by measuring the line emission arising from an extended accretion disk. For each of the galaxies in our sample we have measured the rotation curve and determined the mass distribution within the inner 5–50 pc. We have modeled the stellar mass component using the photometric data from existing HST images and using both data sets we have derived the masses of the black holes in each galaxy. These results will be very important in clarifying the role of the black hole in powering the AGN, will shed light into the effectiveness of the accretion mechanisms and finally will be important in addressing the fundamental issue of unification for Seyfert 1 and Seyfert 2 galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have reanalyzed in a consistent way existing reverberation data for 35 AGNs for the purpose of refining the black hole masses derived from these data. We find that the precision (or random component of the error) of reverberation-based black hole mass measurements is typically around 30%, comparable to the precision attained in measurement of black hole masses in quiescent galaxies by gas or stellar dynamical methods. As discussed in this volume by Onken et al., we have established an absolute calibration for AGN reverberation-based masses by assuming that AGNs and quiescent galaxies follow an identical relationship between black hole mass and host-galaxy bulge velocity dispersion. The scatter around this relationship implies that the typical systematic uncertainties in reverberation-based black hole masses are smaller than a factor of three. We present a preliminary version of a mass–luminosity relationship that is much better defined than any previous attempt. Scatter about the mass–luminosity relationship for these AGNs appears to be real and could be correlated with either Eddington ratio or source inclination.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

I review the evidence in favour of the existence of intermediate mass black holes (IMBH) in a sub-set of the class of ultraluminous X-ray source (ULX). Their X-ray properties and information on their local environments is beginning to point towards the presence of IMBHs in some, and perhaps the most luminous, ULX.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate the relation between circular velocity vc and bulge velocity dispersion σ in spiral galaxies, based on literature data and new spectroscopic observations. We find a strong, nearly linear vc−σ correlation with a negligible intrinsic scatter, and a striking agreement with the corresponding relation for elliptical galaxies. The least massive galaxies (σ<80 km s−1) significantly deviate from this relation. We combine this vc−σ correlation with the well-known MBHσ relation to obtain a tight correlation between circular velocity and supermassive black hole mass, and interpret this as observational evidence for a close link between supermassive black holes and the dark matter haloes in which they presumably formed. Apart from being an important ingredient for theoretical models of galaxy formation and evolution, the relation between MBH and circular velocity has the potential to become an important practical tool in estimating supermassive black hole masses in spiral galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of UV spectroscopy of AGNs with double-peaked Balmer emission lines. In 2/3 of the objects, the far-UV resonance lines are strong, with single-peaked profiles resembling those of Seyfert galaxies. The Mg II line is the only UV line with a double-peaked profile. In the remaining objects, the far-UV resonance lines are relatively weak but still single-peaked. The latter group also displays prominent UV absorption lines, indicative of a low-ionization absorber. We interpret the difference in the profiles of the emission lines as resulting from two different regions: a dense, low-ionization accretion disk (the predominant source of the Balmer and Mg II lines), and a lower density, higher-ionization wind (the predominant source of the far-UV resonance lines). These results suggest a way of connecting the double-peaked emitters with the greater AGN population: in double-peaked emitters the accretion rate onto the black hole is low, making the wind feeble and allowing the lines from the underlying disk to shine through. This scenario also implies that in the majority of AGNs, the wind is the source of the broad emission lines.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the first homogeneous sample of intermediate-mass black hole candidates in active galactic nuclei. Starting with broad-line active nuclei from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling relation to select a sample of 19 galaxies in the mass range $M_{\mathrm{BH}} \approx 8 \times 10^4 - 10^6\,\ensuremath{M_{\odot}}$. In contrast to the local active galaxy population, the host galaxies are ∼1 mag fainter than M* and thus are probably late-type systems. The active nuclei are also faint, with $M_g \approx -15$ to −18 mag, while the bolometric luminosities are close to the Eddington limit. The spectral properties of the sample are compared to the related class of objects known as narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as observational analogues of primordial black holes, contributors to the integrated signal for future gravitational wave experiments, and as a valuable tool in the calibration of the MBM–σ∗ relation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have taken N-band spectra of the nuclear dust regions of NGC 1068 with the newly commissioned Mid-InfrareD-Interferometer (MIDI), with a spatial resolution of ∼10 milliarcsec (∼1 pc). We resolve the near-nuclear emission into a warm component (∼300 K) 2.1×3.4 pc in size and a smaller hot component. We see a strong silicate absorption in front of the central component that differs in form from normal olivine-type profiles. This thick dust structure cannot be supported for the length of the active phase of the AGN by gas pressure or turbulent motions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Past X-ray observations by ASCA suggest that warm absorbers (O VII and O VIII edges) are apparently rare in high luminosity AGNs (quasars) while they are more common in low luminosity AGNs (Seyferts). However, this could be a selection effect if high luminosity AGNs have mostly narrow absorption lines (with no strong bound free edges), which escaped detection by the low resolution of ASCA. To check this hypothesis we are studying the high-resolution X-ray spectra of quasars from grating spectrometers on board Chandra and XMM-Newton in search for absorption lines. In this contribution we present spectra of three quasars. The spectra show narrow (several hundred km s−1) absorption and emission X-ray lines from H-like and He-like ions of O, Ne, Mg, and other abundant elements. We also detect absorption from iron L-shell lines and iron M-shell unresolved transition array. We present the analysis of MR2251-178 where we find that at least two, and probably three, distinct warm absorbers are needed to explain the high resolution spectrum of this object. We re-analyze the high-resolution X-ray spectrum of PG 1211+143 and suggest that an outflow velocity of ∼3000 km s−1 provides an adequate explanation to these data. We also present preliminary results form the Chandra/HETGS observation of the quasar 4C74.26.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss follow-up X-ray observations of giant-amplitude, non-recurrent X-ray flares, interpreted as tidal disruptions of stars by supermassive black holes at the centers of the flaring galaxies. The flare observations open up a new window to study supermassive black holes and their environment, and the physics of accretion events, in non-active galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We quantify the importance of mass accretion during AGN phases in the growth of supermassive black holes (BH) by comparing the mass function of black holes in the local universe with that expected from AGN relics, which are black holes grown entirely with mass accretion during AGN phases. The local BH mass function (BHMF) is estimated by applying the well-known correlations between BH mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and velocity functions. The density of BHs in the local universe is $\rhoBH = 4.6_{-1.4}^{+1.9}\, h_{0.7}^2 \rhoBHunits$. The relic BHMF is derived from the continuity equation with the only assumption that AGN activity is due to accretion onto massive BHs and that merging is not important. We find that the relic BHMF at z = 0 is generated mainly at z<3. Moreover, the BH growth is anti-hierarchical in the sense that smaller BHs ($M_{BH}<10^{7}M_\odot$) grow at lower redshifts (z<1) with respect to more massive ones (z∼1−3). Unlike previous work, we find that the BHMF of AGN relics is perfectly consistent with the local BHMF indicating the local BHs were mainly grown during AGN activity. This agreement is obtained while satisfying, at the same time, the constraints imposed from the X-ray background. The comparison with the local BHMF also suggests that the merging process is not important in shaping the relic BHMF, at least at low redshifts (z<3). Our analysis thus suggests the following scenario: local black holes grew during AGN phases in which accreting matter was converted into radiation with efficiencies ε = 0.04−0.16 and emitted at a fraction λ = 0.1−1.7 and emitted at a fraction λ = 0.1−1.7 of the Eddington luminosity. The average total lifetime of these active phases ranges from $\simeq 4.5\times 10^{8}$ yr for $M_{BH}<10^{8}M_\odot$ to $\simeq 1.5\xten{8}$ yr for $M_{BH}>10^{9}M_\odot$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present new observations in X-ray and optical/ultraviolet of the nucleus of NGC 1097 known for the abrupt appearance of broad, double-peaked Balmer lines in its spectrum in 1991. These new observations are used to construct the spectral energy distribution (SED) of the central engine. From the SED we infer that this AGN is radio-loud and has a bolometric luminosity $L_{\rm Bol} \sim 10^{42} \: \textrm{erg s}^{-1}$, implying a low Eddington ratio of $L_{\rm Bol}/L_{\rm Edd} \sim 10^{-4}$. These results suggest that the central ionizing source is an advection-dominated accretion flow (ADAF) in the form of an ellevated structure which photoionizes an outer thin disk. We fit a simplified ADAF model to the SED and obtain limits on the values of the mass accretion rate $\dot{M}$ and accretion efficiency η, namely $\dot{M}/{\dot{M}_{\rm Edd}} \gtrsim 10^{-3}$ and $\eta \lesssim 10^{-2}$. We identify an ‘energy budget’ problem: if the central photoionizing source is isotropic, the covering factor of the line-emitting portion of the thin accretion disk is ≈6, i. e. the central source accounts for only 20% of the energy emitted in the double-peaked Balmer lines.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

First results from the AGN-Heidelberg program aimed at spatially resolving the central pc region of the closest Active Galactic Nuclei are presented. The core region of prototype active nuclei are clearly unveiled at IR waves and at distances from the nucleus – few pc- where circumnuclear starforming regions appear not to be present. Within that perspective, classical active nuclei as Circinus and NGC 1097, reveal with unprecedented detail clear channels of material being driven to the core whereas others as Centaurus A and NGC 5506, show a “clean” core environment. At the very center, a central compact region of ∼2 pc scale is resolved in Circinus but not in the other cases challenging thus the universal presence of the putative obscuring torus.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present Chandra observations of the nuclear region of nearby inactive galaxies. The sample is selected based on the absence or weakness of optical emission lines in the nucleus. X-ray nuclei are detected in four out of six galaxies. This result, along with previous observations, suggests that more than half of galaxies, for which no evidence for nuclear activity is known, possess an ultra-low-luminosity “active” nucleus. X-ray emission from hot gas is detected in at least four galaxies. We estimate the Bondi accretion rate from the gas density, temperature, and central black hole mass and suggest that the accretion luminosity is not simply determined by the Bondi rate.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We show that Massive Black Holes of AGNs follow the same approximately linear relation with the luminosity of the host spheroid (bulge) found in normal (quiescent) galaxies, with the black hole mass being 0.002 that of the bulge. We also demonstrate that Narrow line AGNs seem to have a significantly lower Mbh/Lbulge ratio, which implies a new strong correlation between Mbh/Lbulge and the width of the broad emission lines of AGNs (Wandel 2002). Combining existing data, new observations and extrapolation schemes based on the Faber-Jackson relation, the relation between the BH mass and the stellar velocity dispersion in the host bulge of AGNs is constructed. It too agrees with the relation found in quiescent galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The detection of very high energy emission in blazars with the new generation of TeV telescopes rises the question of the origin of this emission and its relation to that at other wavelengths. In this work we present contemporaneous optical and X-ray observations of two bright and close southern hemisphere blazars: PKS 2005-489 and PKS 2155-304, the latter detected at TeV energies. The SED between radio and X-rays is discussed and compared with that of other TeV blazars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Results gathered to anchor the MBH−σ∗ relation raise concerns in the methods of measuring of σ∗ used for the original slope determinations. We present these preliminary results to demonstrate the problem and briefly outline where the discrepancies arise. IFS is a valuable tool in addressing this area and will allow us to remove systematics before tightening the MBH−σ∗ relation and end the “aperture arguments”.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We identify the dominant emission processes in 3C 270 in the infrared to be non-thermal, and emission from its dusty disk does not contribute significantly to the total infrared output. This implies that such disks can be hard to find through their infrared emission, and that any circumnuclear torus, if at all present, is small and thin.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

It is possible that narrow-line Seyfert 1 galaxies (NLS1s) are in the early stage of active galactic nuclei (AGNs) evolution. It is important to estimate the mass of supermassive black hole (SBH) in NLS1s. Here we considered the different kinds of methods to estimate the SBH masses in NLS1s. The virial mass from the Hβ linewidth assuming random orbits of broad line regions (BLRs) is consistent with that from the statured soft X-ray luminosity, which showed that most of NLS1s are in the super-Eddington accretion state. The mass from the [O III] linewidth is systematically larger than that from above two methods. It is necessary to measure he bulge stellar dispersion and/or bulge luminosity in NLS1s.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

There is a tight M−σ relation in nearby inactive galaxies. Nearby radio-quiet AGNs also followed this relation. In order to investigate whether radio-loud AGNs and NLS1s follow this relation or not, we estimated their central black hole masses from Hβ and the bulge velocity dispersions from [O III] linewidth. We found that radio-loud AGNs and NLS1s seemed to deviate from this relation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html