by Blecha, Laura and Loeb, Abraham and Narayan, Ramesh
20 pages, 9 figures. Submitted to MNRAS

We present a first attempt to model the narrow-line (NL) region of active galactic nuclei (AGN) in hydrodynamic simulations of galaxy mergers, using a novel physical prescription. This model is used to determine the origin of double-peaked NL (dNL) AGN in merging galaxies and their connection to supermassive black hole (SMBH) pairs, motivated by recent observations of such objects. We find that dNL AGN induced by the relative motion of SMBH pairs are a generic but short-lived feature of gaseous major mergers. dNL AGN are most likely to be observed in late-stage mergers, during the kpc-scale phase of SMBH inspiral or soon after the SMBH merger. However, even within the kpc-scale phase, only a minority of dNL AGN are directly induced by SMBH motion; their lifetimes are typically a few Myr. Most double peaks arise from gas kinematics near the SMBH, although prior to the SMBH merger up to 80% of all dNL profiles may be influenced by SMBH motion via altered peak ratios or velocity offsets. The total lifetimes of dNL AGN depend strongly on viewing angle and on properties of the merging galaxies. Also, in a typical merger, at least 10-40% of the double peaks induced by SMBH motion have small projected separations, 0.1-1 kpc, such that dual peaks of stellar surface brightness are not easily resolved. Diffuse tidal features can indicate late-stage galaxy mergers, although they do not distinguish SMBH pairs from merged SMBHs. We show that dNL profiles with peak velocity splittings > 500 km s^-1 or with measurable overall velocity shifts are often associated with SMBH pairs. Our results support the notion that selection of dNL AGN is a promising method for identifying dual SMBH candidates, but demonstrate the critical importance of high-resolution, multi-wavelength follow-up observations, and the use of multiple lines of evidence, for confirming the dual nature of candidate SMBH pairs. (Abridged)

by Zubovas, Kastytis and King, Andrew R.
6 pages, 1 figure, 2 tables; accepted for publication in ApJ Letters

It is widely suspected that AGN activity ultimately sweeps galaxies clear of their gas. We work out the observable properties required to achieve this. Large-scale AGN-driven outflows should have kinetic luminosities $latex \sim \eta\le/2 \sim 0.05\le$ and momentum rates $latex \sim 20\le/c$, where $latex \le$ is the Eddington luminosity of the central black hole and $latex \eta\sim 0.1$ its radiative accretion efficiency. This creates an expanding two-phase medium in which molecular species coexist with hot gas, which can persist after the central AGN has switched off. This picture predicts outflow velocities $latex \sim 1000 – 1500$ km\,s$latex ^{-1}$ and mass outflow rates up to $latex 4000 \msun\,{\rm yr}^{-1}$ on kpc scales, fixed mainly by the host galaxy velocity dispersion (or equivalently black hole mass). All these features agree with those of outflows observed in galaxies such as Mrk231. This strongly suggests that AGN activity is what sweeps galaxies clear of their gas on a dynamical timescale and makes them red and dead. We suggest future observational tests of this picture.

by Johannsen, Tim and Psaltis, Dimitrios and Gillessen, Stefan and Marrone, Daniel P. and Ozel, Feryal and Doeleman, Sheperd S. and Fish, Vincent L.
7 pages, 4 figures, 2 tables, submitted to ApJ

Dynamical mass measurements to date have allowed determinations of the mass M and the distance D of the galactic center black hole Sgr A* as well as those of other nearby supermassive black holes. In the case of Sgr A*, these measurements are limited by a degeneracy between the mass and distance scaling roughly as M ~ D^2. Future very-long baseline interferometric observations will image a bright and narrow ring surrounding the shadow of the supermassive black hole, if its accretion flow is optically thin. In this paper, we show that the combination of dynamical measurements and VLBI imaging of the ring of Sgr A* breaks the degeneracy between mass and distance. We estimate the signal to noise ratio of near-future VLBI arrays consisting of five to six stations and simulate measurements of the mass and distance of Sgr A* using the expected size of the ring image and existing data of stellar ephemerides. We demonstrate that VLBI observations at 1 mm can already improve the error on the mass by a factor of three compared to the results from the monitoring of stellar orbits alone; observations at 0.5 mm can reduce the error by as much as a factor of 7.5. In addition, we calculate the angular sizes of the bright rings of a number of other nearby supermassive black holes and identify the optimal targets besides Sgr A* that could be imaged by a ground-based VLBI array or a future space-VLBI mission allowing for refined mass measurements.

by Burkert, Andreas and Schartmann, Mark and Alig, Christian and Gillessen, Stefan and Genzel, Reinhard and Fritz, Tobias and Eisenhauer, Frank
22 pages, 13 figures, submitted to ApJ

The origin, structure and evolution of the small gas cloud, G2, is investigated, that is on an orbit almost straight into the Galactic central supermassive black hole (SMBH). G2 is a sensitive probe of the hot accretion zone of Sgr A*, requiring gas temperatures and densities that agree well with models of captured shock-heated stellar winds. Its mass is equal to the critical mass below which cold clumps would be destroyed quickly by evaporation. Its mass is also constrained by the fact that at apocenter its sound crossing timescale was equal to its orbital timescale. Our numerical simulations show that the observed structure and evolution of G2 can be well reproduced if it formed in pressure equilibrium with the surrounding in 1995 at a distance from the SMBH of 7.6e16 cm. If the cloud would have formed at apocenter in the ‘clockwise’ stellar disk as expected from its orbit, it would be torn into a very elongated spaghetti-like filament by 2011 which is not observed. This problem can be solved if G2 is the head of a larger, shell-like structure that formed at apocenter. Our numerical simulations show that this scenario explains not only G2’s observed kinematical and geometrical properties but also the Br_gamma observations of a low surface brightness gas tail that trails the cloud. In 2013, while passing the SMBH G2 will break up into a string of droplets that within the next 30 years mix with the surrounding hot gas and trigger cycles of AGN activity.

by Crocker, Roland M.
30 pages, 35 figures

We construct a simple model of the star-formation- (and resultant supernova-) driven mass and energy flows through the inner ~200 pc (in diameter) of the Galaxy. Our modelling is constrained, in particular, by the non-thermal radio continuum and {\gamma}-ray signals detected from the region. The modelling points to a current star-formation rate of 0.04 – 0.12 M\msun/year at 2{\sigma} confidence within the region with best-fit value in the range 0.08 – 0.12 M\msun/year which – if sustained over 10 Gyr – would fill out the ~ 10^9 M\msun stellar population of the nuclear bulge. Mass is being accreted on to the Galactic centre (GC) region at a rate ~0.3M\msun/year. The region’s star-formation activity drives an outflow of plasma, cosmic rays, and entrained, cooler gas. Neither the plasma nor the entrained gas reaches the gravitational escape speed, however, and all this material fountains back on to the inner Galaxy. The system we model can naturally account for the recently-observed ~> 10^6 ‘halo’ of molecular gas surrounding the Central Molecular Zone out to 100-200 pc heights. The injection of cooler, high-metallicity material into the Galactic halo above the GC may catalyse the subsequent cooling and condensation of hot plasma out of this region and explain the presence of relatively pristine, nuclear-unprocessed gas in the GC. The plasma outflow from the GC reaches a height of a few kpc and is compellingly related to the recently-discovered Fermi Bubbles. Our modelling demonstrates that ~ 10^9 M\msun of hot gas is processed through the GC over 10 Gyr. We speculate that the continual star-formation in the GC over the age of the Milky Way has kept the SMBH in a quiescent state thus preventing it from significantly heating the coronal gas, allowing for the continual accretion of gas on to the disk and the sustenance of star formation on much wider scales in the Galaxy [abridged].

by Agudo, Ivan and Marscher, Alan P. and Jorstad, Svetlana G. and Gomez, Jose L. and Perucho, Manel and Piner, B. Glenn and Rioja, Maria and Dodson, Richard
Accepted for Publication in The Astrophysical Journal. 11 pages, 6 figures, 4 tables. High resolution images on figure 1 and complete tables 1 and 2 may be provided on request

We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 deg. during [2004,2006], as viewed in the plane of the sky, that we interpret as the crossing of the jet from one side of the line of sight to the other during a softer and longer term swing of the inner jet. Modulating such long term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost ~0.4mas of the jet with fluctuations in position angle of up to ~40 deg. over time scales ~2yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short time scales of the observed behavior rules out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow; perhaps related to turbulence in the accretion disk; coupled with hydrodynamic instabilities, leads to the non-ballistic dynamics that cause the observed non-periodic changes in the direction of the inner jet.

by Constantin, Anca and Seth, Anil
11 pages, 4 figures, accepted for publication in Advances in Astronomy

We discuss the peculiar nature of the nucleus of M94 (NGC 4736) in the context of new measurements of the broad H_alpha emission from HST-STIS observations. We show that this component is unambiguously associated with the high-resolution X-ray, radio, and variable UV sources detected at the optical nucleus of this galaxy. These multi-wavelength observations suggest that NGC 4736 is one of the least luminous broad-line (type 1) LINERs, with Lbol = 2.5 \times 10^40 erg/s. This LINER galaxy has also possibly the least luminous broad line region known (LH_alpha =2.2\times10^37 erg/s). We compare black hole mass estimates of this system to the recently measured ~7 \times 10^6 M_sun dynamical black hole mass measurement. The fundamental plane and M-sigma relationship roughly agree with the measured black hole mass, while other accretion based estimates (the M-FWHM(H_alpha) relation, empirical correlation of BH mass with high-ionization mid IR emission lines, and the X-ray excess variance) provide much lower estimates (~10^5 M_sun). An energy budget test shows that the AGN in this system may be deficient in ionizing radiation relative to the observed emission-line activity. This deficiency may result from source variability or the superposition of multiple sources including supernovae.

by Gillessen, S. and Genzel, R. and Fritz, T. K. and Quataert, E. and Alig, C. and Burkert, A. and Cuadra, J. and Eisenhauer, F. and Pfuhl, O. and Dodds-Eden, K. and Gammie, C. F. and Ott, T.
in press at Nature

Measurements of stellar orbits provide compelling evidence that the compact radio source Sagittarius A* at the Galactic Centre is a black hole four million times the mass of the Sun. With the exception of modest X-ray and infrared flares, Sgr A* is surprisingly faint, suggesting that the accretion rate and radiation efficiency near the event horizon are currently very low. Here we report the presence of a dense gas cloud approximately three times the mass of Earth that is falling into the accretion zone of Sgr A*. Our observations tightly constrain the cloud’s orbit to be highly eccentric, with an innermost radius of approach of only ~3,100 times the event horizon that will be reached in 2013. Over the past three years the cloud has begun to disrupt, probably mainly through tidal shearing arising from the black hole’s gravitational force. The cloud’s dynamic evolution and radiation in the next few years will probe the properties of the accretion flow and the feeding processes of the super-massive black hole. The kilo-electronvolt X-ray emission of Sgr A* may brighten significantly when the cloud reaches pericentre. There may also be a giant radiation flare several years from now if the cloud breaks up and its fragments feed gas into the central accretion zone.

by Erwin, Peter and Gadotti, Dimitri
pdflatex, 10 pages, 4 figures. Invited paper for Advances in Astronomy special issue: “Seeking for the Leading Actor on the Cosmic Stage: Galaxies versus Supermassive Black Holes”

Studies have suggested that there is a strong correlation between the masses of nuclear star clusters (NSCs) and their host galaxies, a correlation which said to be an extension of the well-known correlations between supermassive black holes (SMBHs) and their host galaxies. But careful analysis of disk galaxies — including 2D bulge/disk/bar decompositions — shows that while SMBHs correlate with the stellar mass of the bulge component of galaxies, the masses of NSCs correlate much better with the total galaxy stellar mass. In addition, the mass ratio M_nsc/M_star,tot for NSCs in spirals (at least those with Hubble types Sc and later) is typically an order of magnitude smaller than the mass ratio M_bh/M_star, bulge of SMBHs. The absence of a universal “central massive object” correlation argues against common formation and growth mechanisms for both SMBHs and NSCs. We also discuss evidence for a break in the NSC-host galaxy correlation: galaxies with Hubble types earlier than Sbc appear to host systematically more massive NSCs than do types Sc and later.

by Lauer, Tod R. and Bender, Ralf and Kormendy, John and Rosenfield, Philip and Green, Richard F.
29 pages, 11 figures (3 color); Astrophysical Journal accepted

We obtained U_330 and B band images of the M31 nucleus using the High Resolution Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST). The spatial resolution in the U_330-band, 0.03″ FWHM, or 0.1 pc at M31, is sufficient to resolve the outskirts of the compact cluster (P3) of UV-bright stars surrounding the M31 black hole. The center of the cluster is marked by an extended source that is both brighter and redder than the other point sources within P3; it is likely to be a blend of several bright stars. We hypothesize that it marks the location of the M31 black hole. Both stellar photometry and a surface brightness fluctuation analysis, show that the P3 stellar population is consistent with early-type main sequence stars formed in a ~100 – ~200 Myr old starburst population. Evolutionary tracks of post early asymptotic giant-branch stars, associated with late-stage evolution of an old population, also traverse the U and U-B domain occupied by the P3 stars; but we argue that only a few stars could be accounted for that way. PEAGB evolution is very rapid, and there is no progenitor population of red giants associated with P3. The result that P3 comprises young stars is consistent with inferences from earlier HST observations of the integrated light of the cluster. Like the Milky Way, M31 harbors a black hole closely surrounded by apparently young stars.

by Liu, F. K. and Wang, Dong and Chen, Xian
47 pages, 9 figures, 1 table; accepted for publication in ApJ

Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries not only leads to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio $latex q\ga 0.3$ with a minimum possible value $latex q_{\rm min} \simeq 0.05$. For major mergers, the remnant SMBHs can get a kick velocity as high as $latex 2100 km s^{-1}$ in the direction within an angle $latex \la 40^\circ$ relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to “dust poor” AGNs. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

by Lahav, Carmit Gordon and Meiron, Yohai and Soker, Noam
10 pages, 3 figures, 2 tables

We examine the scatter in the correlation between black hole masses and their host bulge masses, and find that the increase of the scatter with mass suggests that mergers alone cannot produce the observed correlation. A simple merger scenario of small galaxies leads to a proportionality relation between the late-time black hole and bulge masses, with intrinsic scatter increasing along the ridge line of the relation as the square root of the mass. By examining a sample of 87 galaxies, we find that the scatter increases with mass more rapidly than expected from the merger-only explanation. We do not dispute that mergers play a role, but our results favour a universal feedback mechanism that works on all scales. We discuss the possibility that the feedback mechanism that operated during galaxy formation involved the presence of a cooling flow.

by Martín, S. and Martín-Pintado, J. and Montero-Castaño, M. and Ho, P. T. P. and Blundell, R.
12 pages, 22 figures. Accepted for publication in Astronomy and Astrophysics

The interstellar region within the few central parsecs around the super-massive black hole, Sgr A* at the very Galactic center is composed by a number of overlapping molecular structures which are subject to one of the most hostile physical environments in the Galaxy. We present high resolution (4″x3″~0.16×0.11 pc) interferometric observations of CN, 13CN, H2CO, SiO, c-C3H2 and HC3N emission at 1.3 mm towards the central ~4 pc of the Galactic center region. Strong differences are observed in the distribution of the different molecules. The UV resistant species CN, the only species tracing all previously identified circumnuclear disk (CND) structures, is mostly concentrated in optically thick clumps in the rotating filaments around Sgr A*. H2CO emission traces a shell-like structure that we interpret as the expansion of Sgr A East against the 50 km/s and 20 km/s giant molecular clouds (GMCs). We derive isotopic ratios 12C/13C~15-45 across most of the CND region. The densest molecular material, traced by SiO and HC3N, is located in the southern CND. The observed c-C3H2/HC3N ratio observed in the region is more than an order of magnitude lower than in Galactic PDRs. Toward the central region only CN was detected in absorption. Apart from the known narrow line-of-sight absorptions, a 90 km/s wide optically thick spectral feature is observed. We find evidences of an even wider (>100 km/s) absorption feature. Around 70-75% of the gas mass, concentrated in just the 27% densest molecular clumps, is associated with rotating structures and show evidences of association with each of the arcs of ionized gas in the mini-spiral structure. Chemical differentiation has been proven to be a powerful tool to disentangle the many overlapping molecular components in this crowded and heavily obscured region.

by Lamastra, Alessandra and Menci, Nicola and Fiore, Fabrizio and Di Porto, Cinzia and Amendola, Luca
19 pages, 6 figures, accepted to MNRAS

We compute the number density of massive Black Holes (BHs) at the centre of galaxies at z=6 in different Dynamical Dark Energy (DDE) cosmologies, and compare it with existing observational lower limits, to derive constraints on the evolution of the Dark Energy equation of state parameter w. Our approach only assumes the canonical scenario for structure formation from the collapse of overdense regions of the Dark Matter dominated primordial density field on progressively larger scales; the Black Hole accretion and merging rate have been maximized in the computation so as to obtain robust constraints on w and on its look-back time derivative w_a. Our results provide independent constraints complementary to those obtained by combining Supernovae, Cosmic Microwave Background and Baryonic Acoustic Oscillations; while the latter concern combinations of w_0 and w_a leaving the time evolution of the state parameter w_a highly unconstrained, the BH abundance mainly provide upper limits on w_a, only weakly depending on w_0. Combined with the existing constraints, our results significantly restrict the allowed region in DDE parameter space, ruling out DDE models not providing cosmic time and fast growth factor large enough to allow for the building up of the observed abundance of BHs; in particular, models with -1.2 \leq w_0 \leq -1 and positive redshift evolution w_a > 0.8 – completely consistent with previous constraints – are strongly disfavoured by our independent constraints from BH abundance. Such range of parameters corresponds to “Quintom” DDE models, with w crossing -1 starting from larger values.

by Comerford, Julia M. and Gerke, Brian F. and Stern, Daniel and Cooper, Michael C. and Weiner, Benjamin J. and Newman, Jeffrey A. and Harrison, Fiona and Madsen, Kristin and Barrows, R. Scott
11 pages, 8 figures, submitted to ApJ

Merger-remnant galaxies with kpc-scale separation dual active galactic nuclei (AGNs) should be widespread as a consequence of galaxy mergers and triggered gas accretion onto supermassive black holes, yet very few dual AGNs have been observed. Galaxies with double-peaked narrow AGN emission lines in the Sloan Digital Sky Survey are plausible dual AGN candidates, but their double-peaked profiles could also be the result of gas kinematics or AGN-driven outflows and jets on small or large scales. To help distinguish between these scenarios, we have obtained spatial profiles of the AGN emission via follow-up longslit spectroscopy of 81 double-peaked narrow-line AGNs in SDSS at 0.03 < z < 0.36 using Lick, Palomar, and MMT Observatories. We find that all 81 systems exhibit double AGN emission components with ~kpc projected spatial separations on the sky, which suggests that they are produced by kpc-scale dual AGNs or kpc-scale outflows, jets, or rotating gaseous disks. In addition, we find that the subsample (58%) of the objects with spatially-compact emission components may be preferentially produced by dual AGNs, while the subsample (42%) with spatially-extended emission components may be preferentially produced by AGN outflows. We also find that for 32% of the sample the two AGN emission components are preferentially aligned with the host galaxy major axis, as expected for dual AGNs orbiting in the host galaxy potential. Our results both narrow the list of possible physical mechanisms producing the double AGN components, and suggest several observational criteria for selecting the most promising dual AGN candidates from the full sample of double-peaked narrow-line AGNs. Using these criteria, we determine the 17 most compelling dual AGN candidates in our sample.

by Gaskell, C. Martin
SF2A-2011: Proceedings of the 2011 annual meeting of the French Society of Astronomy and Astrophysics. G. Alecian, K. Belkacem, S. Collin, R. Samadi and D. Valls-Gabaud (eds), p. 573. 6 pages, 4 figures

A simple refinement is proposed to the Dibai method for determining black hole masses in type-1 thermal AGNs. Comparisons with reverberation mapping black hole masses and host galaxy bulge properties suggest that the method is accurate to +/- 0.15 dex. Contrary to what was thought when the black hole mass – stellar velocity dispersion (”M – sigma”) relationship was first discovered, it does not have a lower dispersion than the black hole mass – bulge luminosity (”M – L”) relationship. The dispersion in the M – L relationship for AGNs decreases strongly with increasing black hole mass or bulge luminosity. This is naturally explained as a consequence of the black hole – bulge relationships being the result of averaging due to mergers. Simulations show that the decrease in dispersion in the M – L relationship with increasing mass is in qualitative agreement with being driven by mergers. The large scatter in AGN black hole masses at lower masses rules out significant AGN feedback. A non-causal origin of the correlations between black holes and bulges explains the frequent lack of supermassive black holes in late-type galaxies, and the lack of correlation of black hole mass with pseudo-bulges.

by Mancini, Luigi and Feoli, Antonio
11 pages, 8 figures, to appear in Astronomy & Astrophysics

Thanks to the angular resolution of modern telescopes and kinematic models, the existence of supermassive black holes (SMBHs) in the inner part of galaxies has been established on quite solid grounds. A possible correlation between the mass of SMBHs and the evolutionary state of their host galaxies is expected. Based on the recent 2D decomposition of mid-infrared Spiter/IRAC images of local galaxies with M_bh measurements, we investigated various scaling laws, studying what the best predictor of the mass of the central SMBHs is. We focused on the M_bh-M_G sigma^2 law, the relation between the mass of SMBHs and the kinetic energy of random motions of the corresponding host galaxies. In order to find the best fit for each of the scaling laws examined, we performed a least-squares regression of M_bh on x for the considered sample of galaxies, x being a whatever known parameter of the galaxy bulge. Our analysis shows that M_bh-M_G sigma^2 law fits the examined experimental data successfully as much as the other known scaling laws and shows a value of chi^2 better than the others, a result which is consistent with previous determinations. This means that a combination of sigma and M_G could be necessary to drive the correlations between M_bh and other bulge properties. This issue has been investigated by a careful analysis of the residuals of the various relations. In order to avoid rushed conclusions on galaxy activity and evolution, the indirect inferring of M_bh from the kinetic energy of random motions should be considered, especially when applied to higher redshift galaxies. This statement is suggested by a reanalysis of the SDSS data used to study the SMBH growth in the nearby Universe. Adopting the M_bh-M_G sigma^2 relation instead of the M_bh-sigma, a radio-quiet/radio-loud dichotomy appears in the SMBH mass distribution of the corresponding SDSS early-type AGN galaxies.

by Farrell, S. and Servillat, M. and Pforr, J. and Maccarone, T. and Knigge, C. and Godet, O. and Maraston, C. and Webb, N. and Barret, D. and Gosling, A. and Belmont, R. and Wiersema, K.
10 pages, 2 figures, submitted to ApJL

We present Hubble Space Telescope and simultaneous Swift X-ray telescope observations of the strongest candidate intermediate mass black hole ESO 243-49 HLX-1. Fitting the spectral energy distribution from X-ray to near-infrared wavelengths showed that the broadband spectrum is not consistent with simple and irradiated disc models, but is well described by a model comprised of an irradiated accretion disc plus a stellar population with a mass ~1E6 Msun. The age of the population cannot be uniquely constrained, with both very young and very old stellar populations allowed. However, the very old solution requires excessively high levels of disc reprocessing and an extremely small disc, leading us to favour the young solution with an age of ~13 Myr. In addition, the presence of dust lanes and the lack of any nuclear activity from X-ray observations of the host galaxy lead us to propose that a gas-rich minor merger may have taken place less than ~200 Myr ago. Such a merger event would explain the presence of the intermediate mass black hole and support a young stellar population.

by Valtonen, Mauri J. and Villforth, Carolin and Wiik, Kaj
to appear in Monthly Notices of Royal Astronomical Society

We study the variation of the optical polarization angle in the blazar OJ287 and compare it with the precessing binary black hole model with a ‘live’ accretion disk. First, a model of the variation of the jet direction is calculated, and the main parameters of the model are fixed by the long term optical brightness evolution. Then this model is compared with the variation of the parsec scale radio jet position angle in the sky. Finally, the variation of the polarization angle is calculated using the same model, but using a magnetic field configuration which is at a constant angle relative to the optical jet. It is found that the model fits the data reasonably well if the field is almost parallel to the jet axis. This may imply a steady magnetic field geometry, such as a large-scale helical field.

by Melia, Fulvio and Falanga, Maurizio and Goldwurm, Andrea
Accepted for Publication in MNRAS, September 26, 2011

The Galaxy’s supermassive black hole, Sgr A*, produces an outburst of infrared radiation about once every 6 hours, sometimes accompanied by an even more energetic flurry of X-rays. The NIR photons are produced by nonthermal synchrotron processes, but we still don’t completely understand where or why these flares originate, nor exactly how the X-rays are emitted. The power-law electrons radiating the infrared light may be partially cooled, so the distribution may be a broken power law with a (”cooling break”) transition frequency. In addition, the emission region appears to be rather compact, possibly restricted to the inner edge of the accretion disk. In that case, the X-ray outburst may itself be due to synchrotron processes by the most energetic particles in this population. In this paper, we examine several key features of this proposal, producing relativistically correct polarimetric images of Sgr A*’s NIR and X-ray flare emission, in order to determine (1) whether the measured NIR polarization fraction is consistent with this geometry, and (2) whether the predicted X-ray to NIR peak fluxes are confirmed by the currently available multi-wavelength observations. We also calculate the X-ray polarization fraction and position angle (relative to that of the NIR photons) in anticipation of such measurements in the coming years. We show that whereas the polarization fraction and position angle of the X-rays are similar to those of the NIR component for synchrotron-cooled emission, these quantities are measurably different when the X-rays emerge from a scattering medium. It is clear, therefore, that the development of X-ray polarimetry will represent a major new tool for studying the spacetime near supermassive black holes.

by Decarli, Roberto and Falomo, Renato and Kotilainen, Jari K. and Hyvonen, Tomi and Uslenghi, Michela and Treves, Aldo
Accepted for publication in Advances in Astronomy. To appear in the special issue: “Seeking for the Leading Actor on the Cosmic Stage: Galaxies versus Supermassive Black Holes”

The Mbh-Mhost relation in quasars has been probed only in a limited parameter space, namely at Mbh~10^9 Msun and Mhost~10^12 Msun. Here we present a study of 26 quasars lying in the low-mass end of the relation, down to Mbh~10^7 Msun. We selected quasars from the SDSS and HST-FOS archives, requiring modest Mbh (as derived through the virial paradigm). We imaged our sources in H band from the Nordic Optical Telescope. The quasar host galaxies have been resolved in 25 out of 26 observed targets. Host galaxy luminosities and stellar masses are computed, under reasonable assumptions on their star formation histories. Combining these results with those from our previous studies, we manage to extend the sampled parameter space of the Mbh-Mhost relation in quasars. The relation holds over 2 dex in both the parameters, similarly to what observed in low-luminosity AGN and in quiescent galaxies. For the first time, we are able to measure the slope of the Mbh-Mhost relation in quasars. We find that it is consistent with the linear case (similarly to what observed in quiescent galaxies). We do not find any evidence of a population of massive black holes lying below the relation.

by Yusef-Zadeh, F. and Bushouse, H. and Wardle, M.
16 pages, 7 figures, ApJ, in press

We present HST/NICMOS data to study the surface brightness distribution of stellar light within the inner 10″ of Sgr A* at 1.4, 1.7 and 1.9 microns. We use these data to independently examine the surface brightness distribution that had been measured previously with NICMOS and to determine whether there is a drop in the surface density of stars very near Sgr A*. Our analysis confirms that a previously reported drop in the surface brightness within 0.8″ of Sgr A* is an artifact of bright and massive stars near that radius. We also show that the surface brightness profile within 5″ or ~0.2 pc of Sgr A* can be fitted with broken power laws. The power laws are consistent with previous measurements, in that the profile becomes shallower at small radii. For radii > 0.7″ the slope is beta=-0.34\pm0.04 where Sigma is proportional to r^beta and becomes flatter at smaller radii with beta=-0.13\pm0.04. Modeling of the surface brightness profile gives a stellar density that increases roughly as r^-1 within the inner 1″ of Sgr A*. This slope confirms earlier measurements in that it is not consistent with that expected from an old, dynamically-relaxed stellar cluster with a central supermassive black hole. Assuming that the diffuse emission is not contaminated by a faint population of young stars down to the 17.1 magnitude limit of our imaging data at 1.70$latex \mu$, the shallow cusp profile is not consistent with a decline in stellar density in the inner arcsecond. In addition, converting our measured diffuse light profile to a stellar mass profile, with the assumption that the light is dominated by K0 dwarfs, the enclosed stellar mass within radius r < 0.1 pc of Sgr A* is ~ 3.2×10^4 M_solar (r/0.1 {pc})^2.1.

by Nobukawa, Masayoshi and Ryu, Syukyo G. and Tsuru, Takeshi Go and Koyama, Katsuji
4 pages, 3 figures, accepted for publication in ApJL

Prominent K-shell emission lines of neutral iron (hereafter, FeI-K) and hard-continuum X-rays were found from molecular clouds (MCs) in the Sagittarius B (Sgr B) region with the two separate Suzaku observations in 2005 and 2009. The X-ray flux of FeI-K decreased in correlation to the hard-continuum flux by factor of 0.4-0.5 in 4 years, which is nearly equal to the light-travelling across the MCs. The rapid and correlated time-variability, the equivalent width of FeI-K, and the K-edge absorption depth of FeI are consistently explained by “X-ray echoes” due to the fluorescent and Thomson-scattering of an X-ray flare from an external source. The required flux of the X-ray flare depends on the distance to the MCs and the duration time. The flux, even in the minimum case, is larger than those of the brightest Galactic X-ray sources. Based on these facts, we conclude that the super-massive black hole, Sgr A*, exhibited a big-flare about a few hundred years ago and the luminosity of higher than 4×10^39 erg s^{-1}. The “X-ray echo” from Sgr B, located at a few hundred light-years from Sgr A*, now arrived at the Earth.

by Gil-Merino, Rodrigo and Goicoechea, Luis J. and Shalyapin, Vyacheslav N. and Braga, Vittorio F.
21 pages, 7 text pages, 13 figures, 2 tables, accepted by The Astrophysical Journal

We present the results of our X-ray, UV and optical monitoring campaign of the first gravitationally lensed AGN from late 2009 to mid 2010. The trailing (B) image of the AGN 0957+561 shows the intrinsic continuum variations that were predicted in advance based on observations of the leading (A) image in the gr optical bands. This multiwavelength variability of the B image allows us to carry out a reverberation mapping analysis in the radio-loud AGN 0957+561 at redshift z = 1.41. We find that the U-band and r-band light curves are highly correlated with the g-band record, leading and trailing it by 3 +/- 1 days (U band) and 4 +/- 1 days (r band). These 1-sigma measurements are consistent with a scenario in which flares originated in the immediate vicinity of the supermassive black hole are thermally reprocessed in a standard accretion disk at about 10-20 Schwarzschild radii from the central dark object. We also report that the light curve for the X-ray emission with power-law spectrum is delayed with respect to those in the Ugr bands by about 32 days. Hence, the central driving source can not be a standard corona emitting the observed power-law X-rays. This result is also supported by X-ray reprocessing simulations and the absence of X-ray reflection features in the spectrum of 0957+561. We plausibly interpret the lack of reflection and the 32-day delay as evidence for a power-law X-ray source in the base of the jet at a typical height of about 200 Schwarzschild radii. A central EUV source would drive the variability of 0957+561.

by Fiore, F. and Puccetti, S. and Grazian, A. and Menci, N. and Shankar, F. and Santini, P. and Piconcelli, E. and Koekemoer, A. M. and Fontana, A. and Boutsia, K. and Castellano, M. and Lamastra, A. and Malacaria, C. and Feruglio, C. and Mathur, S. and Miller, N. and Pannella, M.
A&A in press

We present detection and analysis of faint X-ray sources in the Chandra deep field south (CDFS) using the 4 Msec Chandra observation and adopting a new detection algorithm, based on a targeted search at the position of known high-z galaxies. This optimized technique results in the identification of 54 z>3 AGNs, 29 of which are new detections. Applying stringent completeness criteria, we derive AGN luminosity functions in the redshift bins 3-4, 4-5 and >5.8 and for 42.75<log L(2-10 keV)3 (18+17-10%). Their optical counterparts are not strongly reddened and we thus conclude that the size of the X-ray absorber is likely smaller than the dust sublimation radius. We finally report the discovery of a highly star-forming galaxy at z=3.47. If confirmed, this would be one of the farthest objects in which stellar sources are detected in X-rays.

by Schulze, Andreas and Wisotzki, Lutz
20 pages, 20 figures, accepted for publication in A&A

We present an investigation of sample selection effects that influence the observed black hole – bulge relations and its evolution with redshift. We provide a common framework in which all kinds of selection effects on the BH-bulge relations can be investigated, but our main emphasis is on the consequences of using broad-line AGN and their host galaxies to search for evolution in the BH-bulge relation. We identified relevant sources of bias that were not discussed in the literature so far. A particularly important effect is caused by the fact that the active fraction among SMBHs varies considerably with BH mass, in the sense that high-mass BHs are less likely to be active than lower mass ones. In the connection with intrinsic scatter of the BH-bulge relation this effect implies a bias towards a low BH mass at given bulge property. This effect adds to the bias caused by working with luminosity or flux limited samples that were already discussed by others. A quantitative prediction of these biases requires (i) a realistic model of the sample selection function, and (ii) knowledge of relevant underlying distribution functions. For low-redshift AGN samples we can naturally reproduce the flattening of the relation observed in some studies. When extending our analysis to higher redshift samples we are clearly hampered by limited empirical constraints on the various relevant distribution functions. Using a best-guess approach for these distributions we estimate the expected magnitude of sample selection biases for a number of recent observational attempts to study the BH-bulge evolution. In no case do we find statistically significant evidence for an evolving BH-bulge relation. We suggest a possible practical approach to circumvent several of the most problematic issues connected with AGN selection; this could become a powerful diagnostic in future investigations (abridged).

by Barrows, R. Scott and Stern, Daniel and Madsen, Kristin and Harrison, Fiona and Assef, Roberto J. and Comerford, Julia M. and Cushing, Michael C. and Fassnacht, Christopher D. and Gonzalez, Anthony and Griffith, Roger and Hickox, Ryan and Kirkpatrick, J. Davy and Lagattuta, David J.
18 pages and 9 figures. Accepted for publication in The Astrophysical Journal

The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Bootes field, shows double-peaked rest-frame optical/UV emission lines, separated by 0.69″ (5.5 kpc) in the spatial dimension and by 690 km s^-1 in the velocity dimension. The high excitation lines and emission line ratios indicate both systems are ionized by an AGN continuum, and the double-peaked profile resembles that of candidate dual AGN. At a redshift of z=1.175, this source is the highest redshift candidate dual AGN yet identified. However, many sources have similar emission line profiles for which other interpretations are favored. We have analyzed the substantial archival data available in this field, as well as acquired near-infrared (NIR) adaptive optics (AO) imaging and NIR slit spectroscopy. The X-ray spectrum is hard, implying a column density of several 10^23 cm^-2. Though heavily obscured, the source is also one of the brightest in the field, with an absorption-corrected 2-10 keV luminosity of ~10^45 erg s^-1. Outflows driven by an accretion disk may produce the double-peaked lines if the central engine accretes near the Eddington limit. However, we may be seeing the narrow line regions of two AGN following a galactic merger. While the AO image reveals only a single source, a second AGN would easily be obscured by the significant extinction inferred from the X-ray data. Understanding the physical processes producing the complex emission line profiles seen in CXOJ1426+35 and related sources is important for interpreting the growing population of dual AGN candidates.

by Shields, G. A. and Rosario, D. J. and Junkkarinen, V. and Chapman, S. C. and Bonning, E. W. and Chiba, T.
14 pages, 5 figures. Submitted to The Astrophysical Journal

We present HST and UKIRT spectra and images of the 2 kpc binary quasar LBQS 0103-2753 (z=0.858). The HST images (V- and I-band) show tidal features demonstrating that this system is a major galaxy merger in progress. A two-color composite image brings out knots of star formation along the tidal arc and elsewhere. The infrared spectrum shows that both objects are at the same redshift, and that the discrepant redshift of C IV in component A is a consequence of the BAL absorption in the spectrum of this component. LBQS 0103-2753 is one of the most closely spaced binary QSOs known, and is one of relatively few dual AGN showing confirmed broad emission lines from both components. While statistical studies of binary QSOs suggest that simultaneous fueling of both black holes during a merger may be relatively rare, LBQS 0103-2753 demonstrates that such fueling can occur at high luminosity at a late stage in the merger at nuclear spacing of only a few kpc, without severe obscuration of the nuclei.

by Popovic, Luka C.
The work was presented as an invited talk at special workshop “Spectral lines and super-massive black holes” held on June 10, 2011 as a part of activity within the frame of COST action 0905 “Black holes in a violent universe” and as a part of the 8th Serbian Conference on Spectral Line Shapes in Astrophysics.Sent to New Astronomy Review as a review paper

The broad emission spectral lines emitted from AGNs are our main probe of the geometry and physics of the broad line region (BLR) close to the SMBH. There is a group of AGNs that emits very broad and complex line profiles, showing two displaced peaks, one blueshifted and one redshifted from the systemic velocity defined by the narrow lines, or a single such peak. It has been proposed that such line shapes could indicate a supermassive binary black hole (SMB) system. We discuss here how the presence of an SMB will affect the BLRs of AGNs and what the observational consequences might be.

We review previous claims of SMBs based on broad line profiles and find that they may have non-SMB explanations as a consequence of a complex BLR structure. Because of these effects it is very hard to put limits on the number of SMBs from broad line profiles. It is still possible, however, that unusual broad line profiles in combination with other observational effects (line ratios, quasi-periodical oscillations, spectropolarimetry, etc.) could be used for SMBs detection.

Some narrow lines (e.g., [O\,III]) in some AGNs show a double-peaked profile. Such profiles can be caused by streams in the Narrow Line Region (NLR), but may also indicate the presence of a kilo-parsec scale mergers. A few objects indicated as double-peaked narrow line emitters are confirmed as kpc-scale margers, but double-peaked narrow line profiles are mostly caused by the complex NLR geometry.

We briefly discuss the expected line profile of broad Fe K$latex \alpha$ that probably originated in the accretion disk(s) around SMBs.

Finally we consider rare configurations where a SMB system might be gravitationally lensed by a foreground galaxy, and discuss the expected line profiles in these systems.

by Fabbiano, G. and Junfeng, Wang and Elvis, M. and Risaliti, G.
Preprint (not final) version of a paper to appear in Nature

The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes (MBHs), through accretion and merging. Quasar pairs (6,000-300,000 light-years separation) exemplify the first stages of this gravitational interaction. The final stages, through binary MBHs and final collapse with gravitational wave emission, are consistent with the sub-light-year separation MBHs inferred from optical spectra and light-variability of two quasars. The double active nuclei of few nearby galaxies with disrupted morphology and intense star formation (e.g., NGC 6240 and Mkn 463; ~2,400 and ~12,000 light-years separation respectively) demonstrate the importance of major mergers of equal mass spirals in this evolution, leading to an elliptical galaxy, as in the case of the double radio nucleus (~15 light-years separation) elliptical 0402+379. Minor mergers of galaxies with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active MBH pairs, but have hitherto not been seen. Here we report the presence of two active MBHs, separated by ~430 light-years, in the Seyfert galaxy NGC 3393. The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the MBHs embedded in the bulge, suggest the result of minor merger evolution.

by Fabian, A. C. and Zoghbi, A. and Wilkins, D. and Dwelly, T. and Uttley, P. and Schartel, N. and Miniutti, G. and Gallo, L. and Grupe, D. and Komossa, S. and Santos-Lleo, M.
9 pages, 19 figures, MNRAS in press

The Narrow Line Seyfert 1 Galaxy 1H0707-495 went in to a low state from 2010 December to 2011 February, discovered by a monitoring campaign using the X-Ray Telescope on the Swift satellite. We triggered a 100 ks XMM-Newton observation of the source in 2011 January, revealing the source to have dropped by a factor of ten in the soft band, below 1 keV, and a factor of 2 at 5 keV, compared with a long observation in 2008. The sharp spectral drop in the source usually seen around 7 keV now extends to lower energies, below 6 keV in our frame. The 2011 spectrum is well fit by a relativistically-blurred reflection spectrum similar to that which fits the 2008 data, except that the emission is now concentrated solely to the central part of the accretion disc. The irradiating source must lie within 1 gravitational radius of the event horizon of the black hole, which spins rapidly. Alternative models are briefly considered but none has any simple physical interpretation.

by Valtonen, M. J. and Mikkola, S. and Lehto, H. J. and Gopakumar, A. and Hudec, R. and Polednikova, J.
14 pages, 14 figures

We examine the ability to test the black hole no-hair theorem at the 10% level in this decade using the binary black hole in OJ287. In the test we constrain the value of the dimensionless parameter q that relates the scaled quadrupole moment and spin of the primary black hole: q2 = -q 2 . At the present we can say that q = 1 \pm 0.3 (one), in agreement with General Relativity and the no-hair theorems. We demonstrate that this result can be improved if more observational data is found in historical plate archives for the 1959 and 1971 outbursts. We also show that the predicted 2015 and 2019 outbursts will be crucial in improving the accuracy of the test. Space-based photometry is required in 2019 July due the proximity of OJ287 to the Sun at the time of the outburst. The best situation would be to carry out the photometry far from the Earth, from quite a different vantage point, in order to avoid the influence of the nearby Sun. We have considered in particular the STEREO space mission which would be ideal if it has a continuation in 2019 or LORRI on board the New Horizons mission to Pluto.

by Rafter, Stephen and Kaspi, Shai and Behar, Ehud and Kollatschny, Wolfram and Zetzl, Matthias
Accepted for publication in ApJ, 21 pages, 5 figures, 3 tables

We present the results of a reverberation mapping (RM) campaign on the black hole (BH) associated with the active galactic nucleus (AGN) in SDSS J114008.71+030711.4 (hereafter GH08). This object is selected from a sample of 19 candidate intermediate mass BHs (M_{BH} < 10^{6} Msun) found by Greene & Ho 2004 in the Sloan Digital Sky Survey (SDSS). We used the Hobby-Eberly Telescope to obtain 30 spectra over a period of 178 days in an attempt to resolve the reverberation time lag (tau) between the continuum source and the broad line region (BLR) in order to determine the radius of the BLR (R_{BLR}) in GH08. We measure tau to be 2 days with an upper limit of 6 days. We estimate the AGN luminosity at 5100 Angstroms to be approximately 1.1 x 10^{43} erg s^{-1} after deconvolution from the host galaxy. The most well calibrated R_{BLR}-L relation predicts a time lag which is 4 times larger than what we measure. Using the measured H\beta\ full-width-at-half-maximum of 703 (+/-) 110 km s^{-1} and an upper limit for R_{BLR} = 6 light days, we find M_{BH} < 5.8 x 10^{5} Msun as an upper limit to the BH virial mass in GH08, which implies super-Eddington accretion. Based on our measured M_{BH} we propose that GH08 may be another candidate to add to the very short list of AGNs with M_{BH} < 10^{6} Msun determined using RM.

by Noyola, Eva and Baumgardt, Holger
Accepted for publication in ApJ

Surface photometry is a necessary tool to establish the dynamical state of stars clusters. We produce realistic HST-like images from N-body models of star clusters with and without central intermediate-mass black holes (IMBHs) in order to measure their surface brightness profiles. The models contain ~600,000 individual stars, black holes of various masses between 0% to 2% of the total mass, and are evolved for a Hubble time. We measure surface brightness and star count profiles for every constructed image in order to test the effect of intermediate mass black holes on the central logarithmic slope, the core radius, and the half-light radius. We use these quantities to test diagnostic tools for the presence of central black holes using photometry. We find that the the only models that show central shallow cusps with logarithmic slopes between -0.1 and -0.4 are those containing central black holes. Thus, the central logarithmic slope seems to be a good way to choose clusters suspect of containing intermediate-mass black holes. Clusters with steep central cusps can definitely be ruled out to host an IMBH. The measured r_c/r_h ratio has similar values for clusters that have not undergone core-collapse, and those containing a central black hole. We notice that observed Galactic globular clusters have a larger span of values for central slope and r_c/r_h than our modeled clusters, and suggest possible reasons that could account for this and contribute to improve future models.

by Ingram, Adam and Done, Chris
11 pages, 6 figures, 2 tables

Black hole accretion flows show rapid X-ray variability. The Power Spectral Density (PSD) of this is typically fit by a phenomenological model of multiple Lorentzians for both the broad band noise and Quasi-Periodic Oscillations (QPOs). Our previous paper (Ingram & Done 2011) developed the first physical model for the PSD and fit this to observational data. This was based on the same truncated disc/hot inner flow geometry which can explain the correlated properties of the energy spectra. This assumes that the broad band noise is from propagating fluctuations in mass accretion rate within the hot flow, while the QPO is produced by global Lense-Thirring precession of the same hot flow.

Here we develop this model, making some significant improvements. Firstly we specify that the viscous frequency (equivalently, surface density) in the hot flow has the same form as that measured from numerical simulations of precessing, tilted accretion flows. Secondly, we refine the statistical techniques which we use to fit the model to the data. We re-analyse the PSD from the 1998 rise to outburst of XTE J1550-564 with our new model in order to assess the impact of these changes. We find that the derived outer radii of the hot flow (set by the inner radius of the truncated disc) are rather similar, changing from ~68-13 Rg throughout the outburst rise. However, the more physical assumptions of our new model also allow us to constrain the scale height of the flow. This decreases as the outer radius of the flow decreases, as expected from the spectral evolution. The spectrum steepens in response to the increased cooling as the as the truncation radius sweeps in, so gas pressure support for the flow decreases.

The new model, propfluc, is publically available within the xspec spectral fitting package.

by Wardle, Mark and Yusef-Zadeh, Farhad
Submitted to ApJ Letters

Several thin, Keplerian, sub-parsec megamaser disks have been discovered in the nuclei of active galaxies and used to precisely determine the mass of their host black holes. We show that there is an empirical linear correlation between the disk radius and the black hole mass. We demonstrate that such disks are naturally formed by the partial capture of molecular clouds passing through the galactic nucleus and temporarily engulfing the central supermassive black hole. Imperfect cancellation of the angular momenta of the cloud material colliding after passing on opposite sides of the hole leads to the formation of a compact disk. The radial extent of the disk is determined by the efficiency of this process and the Bondi-Hoyle capture radius of the black hole, and naturally produces the empirical linear correlation of the radial extent of the maser distribution with black hole mass. The disk has sufficient column density to allow X-ray irradiation from the central source to generate physical and chemical conditions conducive to the formation of 22 GHz H2O masers. For initial cloud column densities less than ~10^{23.5} cm^-2 the disk is non-self gravitating, consistent with the ordered kinematics of the edge-on megamaser disks; for higher cloud columns the disk would fragment and produce a compact stellar disk similar to that observed around Sgr A* at the galactic centre.

by Gultekin, Kayhan and Richstone, Douglas O. and Gebhardt, Karl and Faber, S. M. and Lauer, Tod R. and Bender, Ralf and Kormendy, John and Pinkney, Jason
10 pages, 8 figures, accepted by ApJ

We present HST STIS observations of the galaxy NGC 4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ration (M/L, V-band) and central black hole mass (M_BH). We find M/L = 3.74 +/- 0.1 (solar units) and M_BH = 1.3 (+5.2, -1.2) \times 10^7 M_sun at an assumed distance of 17.9 Mpc, consistent with no black hole. The upper limit, M_BH < 9.6 \times 10^7 M_sun (2{\sigma}) or M_BH < 1.4 \times 10^8 M_sun (3{\sigma}) is consistent with the current M-{\sigma} relation, which predicts M_BH = 8.8 \times 10^7 M_sun at {\sigma}_e = 182 km/s, but low for the current M-L relation, which predicts M_BH = 7.8 \times 10^8 M_sun at L_V = 8.9 \times 10^10 L_sun,V. HST images show the nucleus to be double, suggesting the presence of a nuclear eccentric stellar disk, in analogy to the Tremaine disk in M31. This conclusion is supported by the HST velocity dispersion profile. Despite the presence of this non-axisymmetric feature and evidence of a recent merger, we conclude that the reliability of our black hole mass determination is not hindered. The inferred low black hole mass may explain the lack of nuclear activity.

by Rafferty, D. A. and Brandt, W. N. and Alexander, D. M. and Xue, Y. Q. and Bauer, F. E. and Lehmer, B. D. and Luo, B. and Papovich, C.
25 pages, 14 figures, accepted for publication in ApJ

We present an analysis of deep multiwavelength data for z ~ 0.3-3 starburst galaxies selected by their 70 um emission in the Extended-Chandra Deep Field-South and Extended Groth Strip. We identify active galactic nuclei (AGNs) in these infrared sources through their X-ray emission and quantify the fraction that host an AGN. We find that the fraction depends strongly on both the mid-infrared color and rest-frame mid-infrared luminosity of the source, rising to ~ 50-70% at the warmest colors and highest mid-infrared luminosities (corresponding to ultraluminous infrared galaxies), similar to the trends found locally. Additionally, we find that the AGN fraction depends strongly on the star formation rate of the host galaxy (inferred from the observed 70 um luminosity after subtracting the estimated AGN contribution), particularly for more luminous AGNs (L_X > 10^43 erg/s). At the highest star formation rates (~ 1000 M_sun/yr), the fraction of galaxies with an X-ray detected AGN rises to ~ 30%, roughly consistent with that found in high-redshift submillimeter galaxies. Assuming that the AGN fraction is driven by the star formation rate (rather than stellar mass or redshift, for which our sample is largely degenerate), this result implies that the duty cycle of luminous AGN activity increases with the star formation rate of the host galaxy: specifically, we find that luminous X-ray detected AGNs are at least ~ 5-10 times more common in systems with high star formation rates (> 300 M_sun/yr) than in systems with lower star formation rates (< 30 M_sun/yr). Lastly, we investigate the ratio between the supermassive black hole accretion rate and the growth rate of the host galaxy and find that, for sources with detected AGNs and star formation, this ratio in distant starbursts agrees well with that expected from the local scaling relation assuming the black holes and bulges grew at the same epoch.

by Lei, Wei-Hua and Zhang, Bing
5 pages, 1 figures

Recently a hard X-ray transient event, Sw J1644+57, was discovered by the Swift satellite, which marks the onset of a relativistic jet from a supermassive black hole, likely triggered by a tidal disruption event (TDE). Another candidate in the same category, Sw J2058+05, was also reported. The low event rate suggests that only a small fraction of TDEs launch relativistic jets. A common speculation is that these rare events are related to rapidly spinning black holes. We attribute jet launching to the Blandford-Znajek mechanism, and use the available data to constrain the black hole spin parameter for the two events. It is found that the two black holes indeed carry a moderate to high spin, suggesting that black hole spin is likely the crucial factor behind the Sw J1644+57 – like events.

by Sazonov, S. and Sunyaev, R. and Revnivtsev, M.
16 pages, 7 figures. Submitted to MNRAS

Chandra has detected optically thin, thermal X-ray emission with a size of ~1 arcsec and luminosity ~10^33 erg/s from the direction of the Galactic supermassive black hole (SMBH), Sgr A*. We suggest that a significant or even dominant fraction of this signal may be produced by several thousand late-type main-sequence stars that possibly hide in the central ~0.1 pc region of the Galaxy. As a result of tidal spin-ups caused by close encounters with other stars and stellar remnants, these stars should be rapidly rotating and hence have hot coronae, emitting copious amounts of X-ray emission with temperatures kT<~ a few keV. The Chandra data thus place an interesting upper limit on the space density of (currently unobservable) low-mass main-sequence stars near Sgr A*. This bound is close to and consistent with current constraints on the central stellar cusp provided by infrared observations. If coronally active stars do provide a significant fraction of the X-ray luminosity of Sgr A*, it should be variable on hourly and daily time scales due to giant flares occurring on different stars. Another consequence is that the quiescent X-ray luminosity and accretion rate of the SMBH are yet lower than believed before.

by Lützgendorf, N. and Kissler-Patig, M. and Noyola, E. and Jalali, B. and de Zeeuw, P. T. and Gebhardt, K. and Baumgardt, H.
12 pages, 12 figures, Accepted for publication in A&A

Intermediate-mass black holes (IMBHs) are of interest in a wide range of astrophysical fields. In particular, the possibility of finding them at the centers of globular clusters has recently drawn attention. IMBHs became detectable since the quality of observational data sets, particularly those obtained with HST and with high resolution ground based spectrographs, advanced to the point where it is possible to measure velocity dispersions at a spatial resolution comparable to the size of the gravitational sphere of influence for plausible IMBH masses. We present results from ground based VLT/FLAMES spectroscopy in combination with HST data for the globular cluster NGC 6388. The aim of this work is to probe whether this massive cluster hosts an intermediate-mass black hole at its center and to compare the results with the expected value predicted by the $latex M_{\bullet} – \sigma$ scaling relation. The spectroscopic data, containing integral field unit measurements, provide kinematic signatures in the center of the cluster while the photometric data give information of the stellar density. Together, these data sets are compared to dynamical models and present evidence of an additional compact dark mass at the center: a black hole. Using analytical Jeans models in combination with various Monte Carlo simulations to estimate the errors, we derive (with 68% confidence limits) a best fit black-hole mass of $latex (17 \pm 9) \times 10^3 M_{\odot}$ and a global mass-to-light ratio of $latex M/L_V = (1.6 \pm 0.3) \ M_{\odot}/L_{\odot}$.

by Iorio, Lorenzo
LaTex2e, 21 pages, 4 tables, no figures

Empirically determining the averaged variations of the orbital parameters of the stars orbiting the Supermassive Black Hole (SBH) hosted by the Galactic Centre (GC) in Sgr A* is, in principle, a valuable tool to put on the test the General Theory of Relativity (GTR), in regimes far stronger than those tested so far, and certain key predictions of it like the no-hair theorems. We analytically work out the long-term variations of all the six osculating Keplerian orbital elements of a test particle orbiting a non-spherical, rotating body with quadrupole moment Q_2 and angular momentum S for a generic spatial orientation of its spin axis k. This choice is motivated by the fact that, basically, we do not know the position in the sky of the spin axis of the SBH in Sgr A* with sufficient accuracy. We apply our results to S2, which is the closest star discovered so far having an orbital period P_b = 15.98 yr, and to a hypothetical closer star X with P_b = 0.5 yr. Our calculations are quite general, not being related to any specific parameterization of k, and can be applied also to astrophysical binary systems, stellar planetary systems, and planetary satellite geodesy in which different reference frames, generally not aligned with the primary’s rotational axis, are routinely used.

by Marti-Vidal, I. and Marcaide, J. M. and Alberdi, A. and Perez-Torres, M. A. and Ros, E. and Guirado, J. C.
16 pages; 13 figures; 8 tables. Submitted to A&A

(See the complete and formatted abstract in the paper). We report on VLBI monitoring of the low-luminosity AGN (LLAGN) in M81 at 1.7, 2.3, 5, and 8.4GHz. These observations are phase-referenced to the supernova SN1993J (located in the same galaxy) and cover from late 1993 to late 2005. The source consists at all frequencies of a slightly resolved core and a small jet extension towards the north-east direction (position angle of ~65 degrees) in agreement with previous publications. We find that the position of the intensity peak in the images at 8.4GHz is very stable in the galactic frame of M81 (proper motion upper limit about 0.010 mas per year). We confirm previous reports that the peaks at all frequencies are systematically shifted among them, possibly due to opacity effects in the jet as predicted by the standard relativistic jet model. We use this model to estimate the magnetic field in the jet and the mass of the central black hole. We obtain a black-hole mass of ~2.e+7 solar masses, comparable to estimates previously reported, but the magnetic fields obtained are thousands of times lower than previous estimates. We find that the positions of the cores at 1.7, 2.3, and 5GHz are less stable than that at 8.4GHz and evolve systematically, shifting southward at a rate of several tens of micro-arcsec per year. The evolution in the jet orientation seems to be related to changes in the inclination of the cores at all frequencies. These results can be interpreted as due to a precessing jet. The jet precession also seems to be related to a flare in the flux densities at 5.0 and 8.4GHz, which lasts ~4 years. A continued monitoring of the flux density and the jet structure evolution in this LLAGN will be necessary to further confirm our jet precession model.

by Schoedel, R. and Morris, M. R. and Muzic, K. and Alberdi, A. and Meyer, L. and Eckart, A. and Gezari, D. Y.
accepted for publication by Astronomy & Astrophysics on 20 June 2011

(abridged) The massive black hole at the center of the Milky Way, SagittariusA* is, in relative terms, the weakest accreting black hole accessible to observations. At the moment, the mean SED of SgrA* is only known reliably in the radio to mm regimes. The goal of this paper is to provide constraints on the mean emission from SgrA* in the near-to-mid infrared. Excellent imaging quality was reached in the MIR by using speckle imaging combined with holographic image reconstruction, a novel technique for this kind of data. No counterpart of SgrA* is detected at 8.6 microns. At this wavelength, SgrA* is located atop a dust ridge, which considerably complicates the search for a potential point source. An observed 3 sigma upper limit of ~10 mJy is estimated for the emission of SgrA* at 8.6 microns, a tighter limit at this wavelength than in previous work. The de-reddened 3 sigma upper limit, including the uncertainty of the extinction correction, is ~84 mJy . Based on the available data, it is argued that, with currently available instruments, SgrA* cannot be detected in the MIR, not even during flares. At 4.8 and 3.8 microns, on the other hand, SgrA* is detected at all times, at least when considering timescales of a few up to 13 min. We derive well-defined time-averaged, de-reddened flux densities of 3.8+-1.3 mJy at 4.8 microns and 5.0+-0.6 mJy at 3.8 microns. Observations with NIRC2/Keck and NaCo/VLT from the literature provide good evidence that SgrA* also has a fairly well-defined de-reddened mean flux of 0.5-2.5 mJy at wavelengths of 2.1-2.2 microns. We present well-constrained anchor points for the SED of SgrA* on the high-frequency side of the Terahertz peak. The new data are in general agreement with published theoretical SEDs of the mean emission from SgrA*, but we expect them to have an appreciable impact on the model parameters in future theoretical work.

by Wong, Ka-Wah and Irwin, Jimmy A. and Yukita, Mihoko and Million, Evan T. and Mathews, William G. and Bregman, Joel N.
5 pages, 4 figures, accepted for publication in the Astrophysical Journal Letters

Gas undergoing Bondi accretion onto a supermassive black hole (SMBH) becomes hotter toward smaller radii. We searched for this signature with a Chandra observation of the hot gas in NGC 3115, which optical observations show has a very massive SMBH. Our analysis suggests that we are resolving, for the first time, the accretion flow within the Bondi radius of a SMBH. We show that the temperature is rising toward the galaxy center as expected in all accretion models in which the black hole is gravitationally capturing the ambient gas. There is no hard central point source that could cause such an apparent rise in temperature. The data support that the Bondi radius is at about 4 arcsec-5 arcsec (188-235 pc), suggesting a SMBH of 2 x 10^9 M_sun that is consistent with the upper end of the optical results. The density profile within the Bondi radius has a power law index of 1.03^{+0.23}_{-0.21} which is consistent with gas in transition from the ambient medium and the accretion flow. The accretion rate at the Bondi radius is determined to be {\dot M}_B = 2.2 x 10^{-2} M_sun yr^{-1}. Thus, the accretion luminosity with 10% radiative efficiency at the Bondi radius (10^{44} ergs s^{-1}) is about six orders of magnitude higher than the upper limit of the X-ray luminosity of the nucleus.

by Eracleous, Michael and Boroson, Todd A. and Halpern, Jules P. and Liu, Jia
Submitted to the Astrophysical Journal Supplements on 10 June 2011. Version with large figures and full object list at: http://www2.astro.psu.edu/users/mce/preprints/SBHB.pdf (5 MB)

[ABRIDGED] We have carried out a systematic search for close supermassive black hole binaries among z < 0.7 SDSS quasars Such binaries are predicted by models of supermassive black hole and host galaxy co-evolution, therefore their census and population properties constitute an important test of these models. We used an automatic technique based on spectroscopic principal component analysis to search for broad H-beta lines that are displaced from the rest-frame of the quasar by more than 1,000 km/s This method can also yield candidates for rapidly recoiling black holes. Our search yielded 88 candidates, several of which were previously identified and discussed in the literature. The widths of the broad H-beta lines are typical among quasars but the shifts are extreme. We found a correlation between the peak offset and skewness of the broad H-beta profiles, which suggests that the profiles we have selected share a common physical explanation. The general properties of the narrow emission lines are typical of quasars. We carried out followup spectroscopic observations of 68 objects to search for changes in the peak velocities of the H-beta lines (the time interval in the observer's frame between the original and new observations is 1-10 yr). We measured significant changes in 14 objects, with resulting accelerations between -120 and +120 km/s/yr. We emphasize that interpretation of the offset broad emission lines as signatures of supermassive binaries is subject to many significant caveats. Many more followup observations over a long temporal baseline are needed to characterize the variability pattern of the broad lines and test that this pattern is indeed consistent with orbital motion. The possibility that some of the objects in this sample are rapidly recoiling black holes remains open as the available data do not provide strong constraints for this scenario.

by Miller, J. M. and Gultekin, K.
Submitted to ApJ Letters

Swift J164449.3+573451 is an exciting transient event, likely powered by the tidal disruption of a star by a massive black hole. The distance to the source, its transient nature, and high internal column density serve to complicate several means of estimating the mass of the culprit black hole. Utilizing newly-refined relationships between black hole mass, radio luminosity, and X-ray luminosity, and de-beaming the source flux, a weak constraint on the black hole mass is obtained: log(Mbh/Msun) = 5.9 +/- 1.1 (1 sigma confidence). This mass range is broad, but it includes low values that are consistent with some variability arguments, and it safely excludes high mass values where it becomes impossible for black holes to disrupt stars. Future refinements in relationships between black hole mass, radio luminosity, and X-ray luminosity will be able to reduce the uncertainty in related mass estimates by a factor of two, making this technique comparable to estimates based on the M-sigma relationship. As near and longer-term survey efforts such as Pan-STARRS, LSST, the Square Kilometer Array, and eROSITA begin to detect many tidal disruption events, black hole mass estimates from combined X-ray and radio observations may prove to be very pragmatic.

by Koss, Michael and Mushotzky, Richard and Treister, Ezequiel and Veilleux, Sylvain and Vasudevan, Ranjan and Miller, Neal and Sanders, D. B. and Schawinski, Kevin and Trippe, Margaret
9 pages, 5 figures, accepted for publication in Astrophysical Journal Letters

We have discovered a binary AGN in the galaxy Mrk 739 using Chandra and Swift BAT. We find two luminous L_2-10 keV=1.1*10^43 and 1.0*10^42 erg/s, unresolved nuclei with a projected separation of 3.4 kpc (5.8\pm0.1) coincident with two bulge components in the optical image. The western X-ray source (Mrk 739W) is highly variable (2.5x) during the 4-hour Chandra observation and has a very hard spectrum consistent with an AGN. While the eastern component was already known to be an AGN based on the presence of broad optical recombination lines, Mrk 739W shows no evidence of being an AGN in optical, UV, and radio observations, suggesting the critical importance of high spatial resolution hard X-ray observations (>2 keV) in finding these binary AGN. A high level of star formation combined with a very low L_[O III]/L_2-10 keV ratio cause the AGN to be missed in optical observations. CO observations of the (3-2) and (2-1) lines indicate large amounts of molecular gas in the system that could be driven towards the black holes during the violent galaxy collision and be key to fueling the binary AGN. Mrk 739E has a high Eddington ratio of 0.71 and a small black hole (log M_BH=7.05\pm0.3) consistent with an efficiently accreting AGN. Other than NGC 6240, this stands as the nearest case of a binary AGN discovered to date.

by Patrick, A. R. and Reeves, J. N. and Lobban, A. P. and Porquet, D. and Markowitz, A. G.
25 pages, 9 figures, accepted for publication in MNRAS

We present a broad-band analysis of deep Suzaku observations of nearby Seyfert 1 AGN: Fairall 9, MCG–6-30-15, NGC 3516, NGC 3783 and NGC 4051. The use of deep observations (exposures >200 ks) with high S/N allows the complex spectra of these objects to be examined in full, taking into account features such as the soft excess, reflection continuum and complex absorption components. After a self-consistent modelling of the broad-band data (0.6-100.0 keV, also making use of BAT data from Swift), the subtle curvature which may be introduced as a consequence of warm absorbers has a measured affect upon the spectrum at energies >3 keV and the Fe K region. Forming a model (including absorption) of these AGN allows the true extent to which broadened diskline emission is present to be examined and as a result the measurement of accretion disc and black hole parameters which are consistent over the full 0.6-100.0 keV energy range.

Fitting relativistic line emission models appear to rule out the presence of maximally spinning black holes in all objects at the 90% confidence level, in particular MCG–6-30-15 at >99.5% confidence. Relativistic Fe K line emission is only marginally required in NGC 3516 and not required in NGC 4051, over the full energy bandpass. Nonetheless, statistically significant broadened 6.4 keV Fe K alpha emission is detected in Fairall 9, MCG–6-30-15 and NGC 3783 yielding black hole spin estimates of a=0.67(+0.10,-0.11), a=0.4(+0.20,-0.12) and a<-0.04 respectively, when fitted with disc emission models.

by Amaro-Seoane, Pau and Miller, M. Coleman and Kennedy, Gareth F.
Submitted to MNRAS

Several galaxies have exhibited X-ray flares that are consistent with the tidal disruption of a star by a central supermassive black hole. In theoretical treatments of this process it is usually assumed that the star was initially on a nearly parabolic orbit relative to the black hole. Such an assumption leads in the simplest approximation to a $latex t^{-5/3}$ decay of the bolometric luminosity and this is indeed consistent with the relatively poorly sampled light curves of such flares. We point out that there is another regime in which the decay would be different: if a binary is tidally separated and the star that remains close to the hole is eventually tidally disrupted from a moderate eccentricity orbit, the decay is slower, typically $latex \sim t^{-1.2}$. As a result, careful sampling of the light curves of such flares could distinguish between these processes and yield insight into the dynamics of binaries as well as single stars in galactic centres. We explore this process using three-body simulations and analytic treatments and discuss the consequences for present-day X-ray detections and future gravitational wave observations.