Browsing by Subject "black hole physics"
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Item Accretion Disk Temperatures Of QSOs: Constraints From The Emission Lines(2013-06) Bonning, E. W.; Shields, Gregory A.; Stevens, A. C.; Salviander, Sarah; Shields, Gregory A.; Stevens, A. C.; Salviander, SarahWe compare QSO emission-line spectra to predictions based on theoretical ionizing continua of accretion disks. The observed line intensities do not show the expected trend of higher ionization with theoretical accretion disk temperature as predicted from the black hole mass and accretion rate. Consistent with earlier studies, this suggests that the inner disk does not reach temperatures as high as expected from standard disk theory. Modified radial temperature profiles, taking account of winds or advection in the inner disk, achieve better agreement with observation. The emission lines of radio-detected and radio-undetected sources show different trends as a function of the theoretically predicted disk temperature.Item Accretion Onto "Seed" Black Holes In The First Galaxies(2009-06) Milosavljevic, Milos; Bromm, Volker; Couch, Sean M.; Oh, S. Peng; Milosavljevic, Milos; Bromm, Volker; Couch, Sean M.The validity of the hypothesis that the massive black holes in high redshift quasars grew from stellar-sized "seeds" is contingent on a seed's ability to double its mass every few 10 million years. This requires that the seed accrete at approximately the Eddington-limited rate. In the specific case of radiatively efficient quasi-radial accretion in a metal-poor protogalactic medium, for which the Bondi accretion rate is often prescribed in cosmological simulations of massive black hole formation, we examine the effects of the radiation emitted near the black hole's event horizon on the structure of the surrounding gas flow. We find that photoheating and radiation pressure from photoionization significantly reduce the steady-Stateaccretion rate and potentially render the quasi-radial accretion flow unsteady and inefficient. The time-averaged accretion rate is always a small fraction of the "Bondi" accretion rate calculated ignoring radiative feedback. The pressure of Ly alpha photons trapped near the H II region surrounding the black hole may further attenuate the inflow. These results suggest that an alternative to quasi-radial, radiatively efficient Bondi-like accretion should be sought to explain the rapid growth of quasar-progenitor seed black holes.Item Accretion onto Intermediate-Mass Black Holes in Dense Protogalactic Clouds(2009-05) Milosavljevi?, Miloš; Couch, Sean M.; Bromm, Volker; Milosavljevi?, Miloš; Couch, Sean M.; Bromm, VolkerWe present the first results from two-dimensional simulations of radiatively efficient accretion of metal-free gas onto intermediate-mass black holes. We fix the shape of the spectral energy distribution of the radiation produced near the event horizon and study the structure of the irradiated low-angular-momentum accretion flow over 3 orders of magnitude in radius from the black hole, 10(14)-10(17) cm for a 100 M(circle dot) black hole. The luminosity of the central source is made to be proportional to the rate at which gas accretes across the inner boundary, which we set just inside the sonic radius. We find that photoionization heating and radiation pressure modify the structure of the flow. When the ambient gas density is 10(7) cm(-3), accretion is intermittent and on average reduced to 32% of the Eddington-limited rate, over 2 orders of magnitude below the "Bondi" rate evaluated ignoring radiation, in agreement with theoretical models. Even if the vicinity of the black hole is supplied with high-density gas, accretion is rendered inefficient through heating and radiation pressure.Item Application Of The Cubed-Sphere Grid To Tilted Black Hole Accretion Disks(2009-01) Fragile, P. Chris; Lindner, Christopher C.; Anninos, Peter; Salmonson, Jay D.; Lindner, Christopher C.In recent work we presented the first results of global general relativistic magnetohydrodynamic (GRMHD) simulations of tilted (or misaligned) accretion disks around rotating black holes. The simulated tilted disks showed dramatic differences from comparable untilted disks, such as asymmetrical accretion onto the hole through opposing "plunging streams" and global precession of the disk powered by a torque provided by the black hole. However, those simulations used a traditional spherical-polar grid that was purposefully under-resolved along the pole, which prevented us from assessing the behavior of any jets that may have been associated with the tilted disks. To address this shortcoming we have added a block-structured "cubed-sphere" grid option to the Cosmos++ GRMHD code, which will allow us to simultaneously resolve the disk and polar regions. Here we present our implementation of this grid and the results of a small suite of validation tests intended to demonstrate that the new grid performs as expected. The most important test in this work is a comparison of identical tilted disks, one evolved using our spherical-polar grid and the other with the cubed-sphere grid. We also demonstrate an interesting dependence of the early-time evolution of our disks on their orientation with respect to the grid alignment. This dependence arises from the differing treatment of current sheets within the disks, especially whether or not they are aligned with symmetry planes of the grid.Item The Black Hole Mass And The Stellar Ring In NGC 3706(2014-02) Gultekin, Kayhan; Gebhardt, Karl; Kormendy, John; Lauer, Tod R.; Bender, Ralf; Tremaine, Scott; Richstone, Douglas O.; Gebhardt, Karl; Kormendy, JohnWe determine the mass of the nuclear black hole (M) in NGC 3706, an early-type galaxy with a central surface brightness minimum arising from an apparent stellar ring, which is misaligned with respect to the galaxy's major axis at larger radii. We fit new HST/STIS and archival data with axisymmetric orbit models to determine M, mass-to-light ratio (gamma(v)), and dark matter halo profile. The best-fit model parameters with l sigma uncertainties are M = (6.0(-0.9)(+0.7)) x 10(8) M-circle dot and gamma(v) = 6.0 +/- 0.2 M-circle dot L-circle dot,v(-1) at an assumed distance of 46 Mpc. The models are inconsistent with no black hole at a significance of Delta X-2 = 15.4 and require a dark matter halo to adequately fit the kinematic data, but the fits are consistent with a large range of plausible dark matter halo parameters. The ring is inconsistent with a population of co- rotating stars on circular orbits, which would produce a narrow line- of- sight velocity distribution (LOSVD). Instead, the ring's LOSVD has a small value of vertical bar V vertical bar/sigma, the ratio of mean velocity to velocity dispersion. Based on the observed low V / a, our orbit modeling, and a kinematic decomposition of the ring from the bulge, we conclude that the stellar ring contains stars that orbit in both directions. We consider potential origins for this unique feature, including multiple tidal disruptions of stellar clusters, a change in the gravitational potential from triaxial to axisymmetric, resonant capture and inclining of orbits by a binary black hole, and multiple mergers leading to gas being funneled to the center of the galaxy.Item The Black Hole Mass-Galaxy Luminosity Relationship For Sloan Digital Sky Survey Quasars(2015-02) Salviander, Sarah; Shields, Gregory A.; Bonning, E. W.; Salviander, Sarah; Shields, Gregory A.We investigate the relationship between the mass of the central supermassive black hole, M-BH, and the host galaxy luminosity, L-gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M-BH-L-gal relationship by examining the redshift dependence of Delta log M-BH, the offset in M-BH from the local M-BH-L-gal relationship. There is little systematic trend in. log MBH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, sigma(*), we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for sigma(*) in statistical studies.Item The Black Hole Mass-Stellar Velocity Dispersion Relationship For Quasars In The Sloan Digital Sky Survey Data Release 7(2013-02) Salviander, Sarah; Shields, Gregory A.; Salviander, Sarah; Shields, Gregory A.We assess evolution in the M-BH-sigma(*) relationship for quasars in the Sloan Digital Sky Survey Data Release 7 for the redshift range 0.1 < z < 1.2. We estimate the black hole mass, M-BH, using the "photoionization method," with the broad H beta or Mg II emission line and the quasar continuum luminosity. For the stellar velocity dispersion, we use the narrow [O III] or [O II] emission line as a surrogate. This study is a follow-up to an earlier study in which we investigated evolution in the M-BH-sigma(*) relationship in quasars from Data Release 3. The greatly increased number of quasars in our new sample has allowed us to break our lower-redshift subsample into black hole mass bins and probe the M-BH-sigma(*) relationship for constant black hole mass. The M-BH-sigma(*) relationship for the highest-mass (M-BH > 10(9.0) M-circle dot) and lowest-mass (M-BH < 10(7.5) M-circle dot) black holes appears to evolve significantly; however, most or all of this apparent evolution can be accounted for by various observational biases due to intrinsic scatter in the relationship and to uncertainties in observed quantities. The M-BH-sigma(*) relationship for black holes in the middle mass range (10(7.5) < M-BH < 10(9.0) M-circle dot) shows minimal change with redshift. The overall results suggest a limit of +/-0.2 dex on any evolution in the M-BH-sigma(*) relationship for quasars out to z approximate to 1 compared with the relationship observed in the local universe. Intrinsic scatter may also provide a plausible way to reconcile the wide range of results of several different studies of the black hole-galaxy relationships.Item The Candidate Intermediate-Mass Black Hole In The Globular Cluster M54(2011-10) Wrobel, J. M.; Greene, J. E.; Ho, L. C.; Greene, J. E.Ibata et al. reported evidence for density and kinematic cusps in the Galactic globular cluster M54, possibly due to the presence of a 9400 M-circle dot black hole. Radiative signatures of accretion onto M54's candidate intermediate-mass black hole (IMBH) could bolster the case for its existence. Analysis of new Chandra and recent Hubble Space Telescope astrometry rules out the X-ray counterpart to the candidate IMBH suggested by Ibata et al. If an IMBH exists in M54, then it has an Eddington ratio of L(0.3-8 keV)/L(Edd) < 1.4 x 10(-10), more similar to that of the candidate IMBH in M15 than that in G1. From new imaging with the NRAO Very Large Array, the luminosity of the candidate IMBH is L(8.5 GHz) < 3.6 x 10(29) erg s(-1) (3 sigma). Two background active galaxies discovered toward M54 could serve as probes of its intracluster medium.Item A Captured Runaway Black Hole in NGC 1277?(2013-07) Shields, G. A.; Bonning, E. W.; Shields, G. A.Recent results indicate that the compact lenticular galaxy NGC 1277 in the Perseus Cluster contains a black hole of mass similar to 10(10) M-circle dot. This far exceeds the expected mass of the central black hole in a galaxy of the modest dimensions of NGC 1277. We suggest that this giant black hole was ejected from the nearby giant galaxy NGC 1275 and subsequently captured by NGC 1277. The ejection was the result of gravitational radiation recoil when two large black holes merged following the merger of two giant ellipticals that helped to form NGC 1275. The black hole wandered in the cluster core until it was captured in a close encounter with NGC 1277. The migration of black holes in clusters may be a common occurrence.Item Collapsar Accretion And The Gamma-Ray Burst X-Ray Light Curve(2010-04) Lindner, Christopher C.; Milosavljevic, Milos; Couch, Sean M.; Kumar, Pawan; Lindner, Christopher C.; Milosavljevic, Milos; Couch, Sean M.; Kumar, PawanWe present axisymmetric hydrodynamical simulations of the long-term accretion of a rotating gamma-ray burst (GRB) progenitor star, a "collapsar," onto the central compact object, which we take to be a black hole. The simulations were carried out with the adaptive-mesh-refinement code FLASH in two spatial dimensions and with an explicit shear viscosity. The evolution of the central accretion rate exhibits phases reminiscent of the long GRB gamma-ray and X-ray light curve, which lends support to the proposal by Kumar et al. that the luminosity is modulated by the central accretion rate. In the first "prompt" phase, the black hole acquires most of its final mass through supersonic quasiradial accretion occurring at a steady rate of similar to 0.2 M(circle dot)s(-1). After a few tens of seconds, an accretion shock sweeps outward through the star. The formation and outward expansion of the accretion shock is accompanied with a sudden and rapid power-law decline in the central accretion rate (M) over dot proportional to t(-2.8), which resembles the L(X) proportional to t(-3) decline observed in the X-ray light curves. The collapsed, shock-heated stellar envelope settles into a thick, low-mass equatorial disk embedded within amassive, pressure-supported atmosphere. After a few hundred seconds, the inflow of low angular momentum material in the axial funnel reverses into an outflow from the thick disk. Meanwhile, the rapid decline of the accretion rate slows down, which is potentially suggestive of the "plateau" phase in the X-ray light curve. We complement our adiabatic simulations with an analytical model that takes into account the cooling by neutrino emission and estimate that the duration of the prompt phase can be similar to 20 s. The model suggests that the steep decline in GRB X-ray light curves is triggered by the circularization of the infalling stellar envelope at radii where the virial temperature is below 10(10) K, such that neutrino cooling is inefficient and an outward expansion of the accretion shock becomes imminent; GRBs with longer prompt gamma-ray emission should have more slowly rotating envelopes.Item Comment On The Black Hole Recoil Candidate Quasar SDSS J092712.65+294344.0(2009-05) Shields, Gregory A.; Bonning, E. W.; Salviander, Sarah; Shields, Gregory A.; Bonning, E. W.; Salviander, SarahThe Sloan Digital Sky Survey (SDSS) quasar J092712.65+294344.0 has been proposed as a candidate for a supermassive black hole (similar to 10(8.8) M(circle dot)) ejected at high speed from the host galactic nucleus by gravitational radiation recoil, or alternatively for a supermassive black hole binary. This is based on a blueshift of 2650 km s(-1) of the broad emission lines ("b-system") relative to the narrow emission lines ("r-system") presumed to reflect the galaxy velocity. New observations with the Hobby-Eberly Telescope (HET) confirm the essential features of the spectrum. We note a third redshift system, characterized by weak, narrow emission lines of [O III] and [O II] at an intermediate velocity 900 km s(-1) redward of the broad-line velocity ("i-system"). A composite spectrum of SDSS QSOs similar to J0927+2943 illustrates the feasibility of detecting the calcium K absorption line in spectra of sufficient quality. The i-system may represent the QSO host galaxy or a companion. Photoionization requires the black hole to be similar to 3 kpc from the r-system emitting gas, implying that we are observing the system only 10(6) yr after the recoil event and contributing to the low probability of observing such a system. The HET observations give an upper limit of 10 km s(-1) per year on the rate of change of the velocity difference between the r- and b-systems, constraining the orbital phase in the binary model. These considerations and the presence of a cluster of galaxies apparently containing J0927+2943 favor the idea that this system represents a superposition of two active galactic nuclei.Item A Dynamical N-Body Model For The Central Region Of Omega Centauri(2012-02) Jalali, B.; Baumgardt, H.; Kissler-Patig, M.; Gebhardt, K.; Noyola, E.; Lutzgendorf, N.; de Zeeuw, P. T.; Gebhardt, K.Context. Supermassive black holes (SMBHs) are fundamental keys to understand the formation and evolution of their host galaxies. However, the formation and growth of SMBHs are not yet well understood. One of the proposed formation scenarios is the growth of SMBHs from seed intermediate-mass black holes (IMBHs, 10(2) to 10(5)M(circle dot)) formed in star clusters. In this context, and also with respect to the low mass end of the M-center dot - sigma relation for galaxies, globular clusters are in a mass range that make them ideal systems to look for IMBHs. Among Galactic star clusters, the massive cluster omega Centauri is a special target due to its central high velocity dispersion and also its multiple stellar populations. Aims. We study the central structure and dynamics of the star cluster omega Centauri to examine whether an IMBH is necessary to explain the observed velocity dispersion and surface brightness profiles. Methods. We perform direct N-body simulations on GPU and GRAPE special purpose computers to follow the dynamical evolution of omega Centauri. The simulations are compared to the most recent data-sets in order to explain the present-day conditions of the cluster and to constrain the initial conditions leading to the observed profiles. Results. We find that starting from isotropic spherical multi-mass King models and within our canonical assumptions, a model with a central IMBH mass of 2% of the cluster stellar mass, i.e. a 5. x 104 M-circle dot IMBH, provides a satisfactory fit to both the observed shallow cusp in surface brightness and the continuous rise towards the center of the radial velocity dispersion profile. In our isotropic spherical models, the predicted proper motion dispersion for the best-fit model is the same as the radial velocity dispersion one. Conclusions. We conclude that with the presence of a central IMBH in our models, we reproduce consistently the rise in the radial velocity dispersion. Furthermore, we always end up with a shallow cusp in the projected surface brightness of our model clusters containing an IMBH. In addition, we find that the M/L ratio seems to be constant in the central region, and starts to rise slightly from the core radius outwards for all models independent of the presence of a black hole. Considering our initial parameter space, it is not possible to explain the observations without a central IMBH for omega Centauri. To further strengthen the presence of an IMBH as a unique explanation of the observed light and kinematics more detailed analysis such as investigating the contribution of primordial binaries and different anisotropy profiles should be studied.Item An Eccentric Circumbinary Accretion Disk And The Detection Of Binary Massive Black Holes(2008-01) MacFadyen, Andrew I.; Milosavljevic, Milos; Milosavljevic, MilosWe present a two-dimensional grid-based hydrodynamic simulation of a thin, viscous, locally isothermal corotating disk orbiting an equal-mass Newtonian binary point mass on a fixed circular orbit. We study the structure of the disk after multiple viscous times. The binary maintains a central hole in the viscously relaxed disk with radius equal to about twice the binary semimajor axis. Disk surface density within the hole is reduced by orders of magnitude relative to the density in the disk bulk. The inner truncation of the disk resembles the clearing of a gap in a protoplanetary disk. An initially circular disk becomes elliptical and then eccentric. Disturbances in the disk contain a component that is stationary in the rotating frame in which the binary is at rest; this component is a two-armed spiral density wave. We measure the distribution of the binary torque in the disk and find that the strongest positive torque is exerted inside the central low-density hole. We make connection with the linear theory of disk forcing at outer Lindblad resonances (OLRs) and find that the measured torque density distribution is consistent with forcing at the 3:2 (m = 2) OLR, well within the central hole. We also measure the time dependence of the rate at which gas accretes across the hole and find quasi-periodic structure. We discuss implications for variability and detection of active galactic nuclei containing a binary massive black hole.Item Effect Of A Dark Matter Halo On The Determination Of Black Hole Masses(2011-03) Schulze, Andreas; Gebhardt, Karl; Gebhardt, KarlStellar dynamical modeling is a powerful method to determine the mass of black holes in quiescent galaxies. However, in previous work the presence of a dark matter halo has been ignored in the modeling. Gebhardt & Thomas in 2009 showed that accounting for a dark matter halo increased the black hole mass of the massive galaxy M87 by a factor of two. We used a sample of 12 galaxies to investigate the effect of accounting for a dark matter halo in the dynamical modeling in more detail, and also updated the masses using improved modeling. The sample of galaxies possesses Hubble Space Telescope and ground-based observations of stellar kinematics. Their black hole masses have been presented before, but without including a dark matter halo in the models. Without a dark halo, we find a mean increase in the estimated mass of 1.5 for the whole sample compared to previous results. We attribute this change to using a more complete orbit library. When we include a dark matter halo, along with the updated models, we find an additional increase in black hole mass by a factor of 1.2 in the mean, much less than for M87. We attribute the smaller discrepancy in black hole mass to using data that better resolve the black hole's sphere of influence. We redetermined the M-center dot-sigma(*) and M-center dot-L-V relationships using our updated black hole masses and found a slight increase in both normalization and intrinsic scatter.Item The Event Horizon Of M87(2015-06) Broderick, Avery E.; Narayan, Ramesh; Kormendy, John; Perlman, Eric S.; Rieke, Marcia J.; Doeleman, Sheperd S.; Kormendy, JohnThe 6 x 10(9) M-circle dot supermassive black hole at the center of the giant elliptical galaxy M87 powers a relativistic jet. Observations at millimeter wavelengths with the Event Horizon Telescope have localized the emission from the base of this jet to angular scales comparable to the putative black hole horizon. The jet might be powered directly by an accretion disk or by electromagnetic extraction of the rotational energy of the black hole. However, even the latter mechanism requires a confining thick accretion disk to maintain the required magnetic flux near the black hole. Therefore, regardless of the jet mechanism, the observed jet power in M87 implies a certain minimum mass accretion rate. If the central compact object in M87 were not a black hole but had a surface, this accretion would result in considerable thermal near-infrared and optical emission from the surface. Current flux limits on the nucleus of M87 strongly constrain any such surface emission. This rules out the presence of a surface and thereby provides indirect evidence for an event horizon.Item The First Galaxies: Assembly With Black Hole Feedback(2012-07) Jeon, Myoungwon; Pawlik, Andreas H.; Greif, Thomas H.; Glover, Simon C. O.; Bromm, Volker; Milosavljevic, Milos; Klessen, Ralf S.; Jeon, Myoungwon; Pawlik, Andreas H.; Bromm, Volker; Milosavljevic, MilosWe study how the first galaxies were assembled under feedback from the accretion onto a central black hole (BH) that is left behind by the first generation of metal-free stars through self-consistent, cosmological simulations. X-ray radiation from the accretion of gas onto BH remnants of Population III (Pop III) stars, or from high-mass X-ray binaries (HMXBs), again involving Pop III stars, influences the mode of second generation star formation. We track the evolution of the BH accretion rate and the associated X-ray feedback starting with the death of the Pop III progenitor star inside a minihalo and following the subsequent evolution of the BH as the minihalo grows to become an atomically cooling galaxy. We find that X-ray photoionization heating from a stellar-mass BH is able to quench further star formation in the host halo at all times before the halo enters the atomic cooling phase. X-ray radiation from an HMXB, assuming a luminosity close to the Eddington value, exerts an even stronger, and more diverse, feedback on star formation. It photoheats the gas inside the host halo, but also promotes the formation of molecular hydrogen and cooling of gas in the intergalactic medium and in nearby minihalos, leading to a net increase in the number of stars formed at early times. Our simulations further show that the radiative feedback from the first BHs may strongly suppress early BH growth, thus constraining models for the formation of supermassive BHs.Item Gemini And Hubble Space Telescope Evidence For An Intermediate-Mass Black Hole In Omega Centauri(2008-04) Noyola, Eva; Gebhardt, Karl; Bergmann, Marcel; Noyola, Eva; Gebhardt, KarlThe globular cluster omega Centauri is one of the largest and most massive members of the galactic system. However, its classification as a globular cluster has been challenged making it a candidate for being the stripped core of an accreted dwarf galaxy; this together with the fact that it has one of the largest velocity dispersions for star clusters in our galaxy makes it an interesting candidate for harboring an intermediate-mass black hole. We measure the surface brightness profile from integrated light on an HSTACS image of the center, and find a central power-law cusp of logarithmic slope -0.08. We also analyze Gemini GMOS-IFU kinematic data for a 5 '' x 5 '' field centered on the nucleus of the cluster, as well as for a field 1400 away. We detect a clear rise in the velocity dispersion from 18.6 km s(-1) at 1400 to 23 km s(-1) in the center. A rise in the velocity dispersion could be due to a central black hole, a central concentration of stellar remnants, or a central orbital structure that is radially biased. We discuss each of these possibilities. An isotropic, spherical dynamical model implies a black hole mass of 4.0(-1.0)(+0.75) x 10(4) M-circle dot, and excludes the no black hole case at greater than 99% significance. We have also run flattened, orbit-based models and find similar results. While our preferred model is the existence of a central black hole, detailed numerical simulations are required to confidently rule out the other possibilities.Item Hydrostatic Gas Constraints On Supermassive Black Hole Masses: Implications For Hydrostatic Equilibrium And Dynamical Modeling In A Sample Of Early-Type Galaxies(2009-10) Humphrey, Phillip J.; Buote, David A.; Brighenti, Fabrizio; Gebhardt, Karl; Mathews, William G.; Gebhardt, KarlWe present new mass measurements for the supermassive black holes (SMBHs) in the centers of three early-type galaxies. The gas pressure in the surrounding, hot interstellar medium (ISM) is measured through spatially resolved spectroscopy with the Chandra X-ray Observatory, allowing the SMBH mass (M(BH)) to be inferred directly under the hydrostatic approximation. This technique does not require calibration against other SMBH measurement methods and its accuracy depends only on the ISM being close to hydrostatic, which is supported by the smooth X-ray isophotes of the galaxies. Combined with results from our recent study of the elliptical galaxy NGC4649, this brings the number of galaxies with SMBHs measured in this way to four. Of these, three already have mass determinations from the kinematics of either the stars or a central gas disk, and hence join only a handful of galaxies with MBH measured by more than one technique. We find good agreement between the different methods, providing support for the assumptions implicit in both the hydrostatic and the dynamical models. The stellar mass-to-light ratios for each galaxy inferred by our technique are in agreement with the predictions of stellar population synthesis models assuming a Kroupa initial mass function (IMF). This concurrence implies that no more than similar to 10%-20% of the ISM pressure is nonthermal, unless there is a conspiracy between the shape of the IMF and nonthermal pressure. Finally, we compute Bondi accretion rates (M(bondi)), finding that the two galaxies with the highest M(bondi) exhibit little evidence of X-ray cavities, suggesting that the correlation with the active galactic nuclei jet power takes time to be established.Item In Search Of The Largest Velocity Dispersion Galaxies(2008-11) Salviander, Sarah; Shields, Gregory A.; Gebhardt, Karl; Bernardi, M.; Hyde, J. B.; Salviander, Sarah; Shields, Gregory A.; Gebhardt, KarlWe present Hobby-Eberly Telescope (HET) observations for galaxies at redshift z < 0:3 from the Sloan Digital Sky Survey (SDSS) showing large velocity dispersions while appearing to be single galaxies in HSTimages. The high signal-to-noise HET spectra provide more definitive velocity dispersions. The maximum velocity dispersion we find is sigma(*) = 444 km s(-1). Emission-line widths in QSOs indicate that black holes can exist with masses M-center dot exceeding 5 billion M-circle dot, implying sigma(*) > 500 km s(-1) by the local M-center dot sigma(*) relationship. This suggests either that QSO black hole masses are overestimated or that the black hole-bulge relationship changes at high black hole mass. The latter option is consistent with evidence that the increase in sigma(*) with luminosity levels off for the brightest elliptical galaxies.Item Is There A Black Hole In NGC 4382?(2011-11) Gultekin, Kayhan; Richstone, Douglas O.; Gebhardt, Karl; Faber, S. M.; Lauer, Tod R.; Bender, Ralf; Kormendy, John; Pinkney, Jason; Gebhardt, KarlWe present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the galaxy NGC 4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ratio (Gamma(V)) and central black hole mass (M-BH). We find Gamma(V) = 3.74 +/- 0.1 M-circle dot/L-circle dot and M-BH = 1.3(-1.2)(+5.2) x 10(7) M-circle dot at an assumed distance of 17.9 Mpc, consistent with no black hole. The upper limit, M-BH < 9.6 x 10(7) M-circle dot (2 sigma) or M-BH < 1.4 x 10(8)(3 sigma), is consistent with the current M-sigma relation, which predicts M-BH = 8.8 x 10(7) M-circle dot at sigma(e) = 182 km s(-1), but low for the current M-L relation, which predicts M-BH = 7.8 x 10(8) M-circle dot at L-V = 8.9 x 10(10) L-circle dot, (V). HST images show the nucleus to be double, suggesting the presence of a nuclear eccentric stellar disk, analogous 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.