Browsing by Subject "scaling relations"
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Item Angular Momenta, Dynamical Masses, And Mergers Of Brightest Cluster Galaxies(2013-12) Tran, Kim-Vy; Brough, Sarah; Gebhardt, Karl; von der Linden, Anja; Couch, Warrick J.; Sharp, Rob; Gebhardt, KarlUsing the VIMOS integral field unit (IFU) spectrograph on the Very Large Telescope, we have spatially mapped the kinematic properties of 10 nearby brightest cluster galaxies (BCGs) and 4 BCG companion galaxies located within a redshift of z = 0.1. In the hierarchical formation model, these massive galaxies (10(10.5) M-circle dot < M-dyn < 10(11.9) M-circle dot) are expected to undergo more mergers than lower mass galaxies, and simulations show that dry minor mergers can remove angular momentum. We test whether BCGs have low angular momenta by using the lambda(Re) parameter developed by the SAURON and ATLAS(3D) teams and combine our kinematics with Sloan Digital Sky Survey photometry to analyze the BCGs' merger status. We find that 30% (3/10) of the BCGs and 100% of the companion galaxies (4/4) are fast rotators as defined by the ATLAS(3D) criteria. Our fastest rotating BCG has a lambda(Re) = 0.35 +/- 0.05. We increase the number of BCGs analyzed from 1 in the combined SAURON and ATLAS(3D) surveys to 11 BCGs total and find that above M-dyn similar to 11.5 M-circle dot, virtually all galaxies, regardless of environment, are slow rotators. To search for signs of recent merging, we analyze the photometry of each system and use the G - M-20 selection criteria to identify mergers. We find that 40% +/- 20% of our BCGs are currently undergoing or have recently undergone a merger (within 0.2 Gyr). Surprisingly, we find no correlation between galaxies with high angular momentum and morphological signatures of merging.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-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 Cold Dust but Warm Gas in the Unusual Elliptical Galaxy NGC 4125(2013-10) Wilson, C. D.; Cridland, A.; Foyle, K.; Parkin, T. J.; Cooper, E. Mentuch; Roussel, H.; Sauvage, M.; Smith, M. W. L.; Baes, M.; Bendo, G.; Boquien, M.; Boselli, A.; Ciesla, L.; Clements, D. L.; Cooray, A.; De Looze, I.; Galametz, M.; Gear, W.; Lebouteiller, V.; Madden, S.; Pereira-Santaella, M.; Remy-Ruyer, A.; Cooper, E. MentuchData from the Herschel Space Observatory have revealed an unusual elliptical galaxy, NGC 4125, which has strong and extended submillimeter emission from cold dust but only very strict upper limits to its CO and Hi emission. Depending on the dust emissivity, the total dust mass is 2-5 x 10(6) M-circle dot. While the neutral gas-to-dust mass ratio is extremely low (<12-30), including the ionized gas traced by [CII] emission raises this limit to <39-100. The dust emission follows a similar r(1/4) profile to the stellar light and the dust to stellar mass ratio is toward the high end of what is found in nearby elliptical galaxies. We suggest that NGC 4125 is currently in an unusual phase where evolved stars produced in a merger-triggered burst of star Formation are pumping large amounts of gas and dust into the interstellar medium. In this scenario, the low neutral gas-to-dust mass ratio is explained by the gas being heated to temperatures >= 10(4) K faster than the dust is evaporated. If galaxies like NGC 4125, where the far-infrared emission does not trace neutral gas in the usual manner, are common at higher redshift, this could have significant implications for our understanding of high redshift galaxies and galaxy evolution.Item Extreme Gas Fractions in Clumpy, Turbulent Disk Galaxies at Z Similar To 0.1(2014-08) Fisher, David B.; Glazebrook, Karl; Bolatto, Alberto; Obreschkow, Danail; Cooper, Erin Mentuch; Wisnioski, Emily; Bassett, Robert; Abraham, Roberto G.; Damjanov, Ivana; Green, Andy; McGregor, Peter; Cooper, Erin MentuchIn this Letter, we report the discovery of CO fluxes, suggesting very high gas fractions in three disk galaxies seen in the nearby universe (z similar to 0.1). These galaxies were investigated as part of the DYnamics of Newly Assembled Massive Objects (DYNAMO) survey. High-resolution Hubble Space Telescope imaging of these objects reveals the presence of large star forming clumps in the bodies of the galaxies, while spatially resolved spectroscopy of redshifted II alpha reveals the presence of high dispersion rotating disks. The internal dynamical state of these galaxies resembles that of disk systems seen at much higher redshifts (1 < z < 3). Using CO(1-0) observations made with the Plateau de Bure Interferometer, we find gas fractions of 20%-30% and depletion times of t(dep) similar to 0.5 Gyr (assuming aMilky-Way-like alpha(CO)). These properties are unlike those expected for low-redshift galaxies of comparable specific star Formation rate, but they are normal for their high-z counterparts. DYNAMO galaxies break the degeneracy between gas fraction and redshift, and we show that the depletion time per specific star Formation rate for galaxies is closely tied to gas fraction, independent of redshift. We also show that the gas dynamics of two of our local targets corresponds to those expected from unstable disks, again resembling the dynamics of high-z disks. These results provide evidence that DYNAMO galaxies are local analogs to the clumpy, turbulent disks, which are often found at high redshift.Item Hunting for Supermassive Black Holes in Nearby Galaxies With the Hobby-Eberly Telescope(2015-05) van den Bosch, Remco C. E.; Gebhardt, Karl; Gultekin, Kayhan; Yildirim, Akin; Walsh, Jonelle L.; Gebhardt, Karl; Walsh, Jonelle L.We have conducted an optical long-slit spectroscopic survey of 1022 galaxies using the 10 m Hobby-Eberly Telescope (HET) at McDonald Observatory. The main goal of the HET Massive Galaxy Survey (HETMGS) is to find nearby galaxies that are suitable for black hole mass measurements. In order to measure accurately the black hole mass, one should kinematically resolve the region where the black hole dominates the gravitational potential. For most galaxies, this region is much less than an arcsecond. Thus, black hole masses are best measured in nearby galaxies with telescopes that obtain high spatial resolution. The HETMGS focuses on those galaxies predicted to have the largest sphere-of-influence, based on published stellar velocity dispersions or the galaxy fundamental plane. To ensure coverage over galaxy types, the survey targets those galaxies across a face-on projection of the fundamental plane. We present the sample selection and resulting data products from the long-slit observations, including central stellar kinematics and emission line ratios. The full data set, including spectra and resolved kinematics, is available online. Additionally, we show that the current crop of black hole masses are highly biased toward dense galaxies and that especially large disks and low dispersion galaxies are under-represented. This survey provides the necessary groundwork for future systematic black hole mass measurement campaigns.Item The L Proportional To Sigma(8) Correlation for Elliptical Galaxies With Cores: Relation With Black Hole Mass(2013-05) Kormendy, John; Bender, Ralf; Kormendy, JohnWe construct the Faber-Jackson correlation between velocity dispersion sigma and total galaxy luminosity L-V separately for elliptical galaxies with and without cores. The coreless ellipticals show the well-known, steep relationship d log sigma/d log L-V = 0.268 or L-V proportional to sigma(3.74). This corresponds to d log sigma/d log M = 0.203, where M is the stellar mass and we use M/L proportional to L-0.32. In contrast, the velocity dispersions of core ellipticals increase much more slowly with L-V and M: d log sigma/d log L-V = 0.120, L-V proportional to sigma(8.33), and d log sigma/d log M = 0.091. Dissipationless major galaxy mergers are expected to preserve sigma according to the simplest virial-theorem arguments. However, numerical simulations show that sigma increases slowly in dry major mergers, with d log sigma/d log M similar or equal to +0.15. In contrast, minor mergers cause sigma to decrease, with d log sigma/d log M similar or equal to -0.05. Thus, the observed relation argues for dry major mergers as the dominant growth mode of the most massive ellipticals. This is consistent with what we know about the Formation of cores. We know no viable way to explain galaxy cores except through dissipationless mergers of approximately equal-mass galaxies followed by core scouring by binary supermassive black holes. The observed, shallow sigma proportional to L-V(+ 0.12) relation for core ellipticals provides further evidence that they formed in dissipationless and predominantly major mergers. Also, it explains the observation that the correlation of supermassive black hole mass with velocity dispersion, M-circle proportional to sigma(4), "saturates" at high M-circle such that M-circle becomes almost independent of sigma.Item The Massive Satellite Population Of Milky-Way-Sized Galaxies(2013-08) Rodriguez-Puebla, Aldo; Avila-Reese, Vladimir; Drory, Niv; Drory, NivSeveral occupational distributions for satellite galaxies more massive than m(*) approximate to 4 x 10(7) M-circle dot around Milky-Way (MW)-sized hosts are presented and used to predict the internal dynamics of these satellites as a function of m(*). For the analysis, a large galaxy group mock catalog is constructed on the basis of (sub) halo-to-stellar mass relations fully constrained with currently available observations, namely the galaxy stellar mass function decomposed into centrals and satellites, and the two-point correlation functions at different masses. We find that 6.6% of MW-sized galaxies host two satellites in the mass range of the Small and Large Magellanic Clouds (SMC and LMC, respectively). The probabilities of the MW-sized galaxies having one satellite equal to or larger than the LMC, two satellites equal to or larger than the SMC, or three satellites equal to or larger than Sagittarius (Sgr) are approximate to 0.26, 0.14, and 0.14, respectively. The cumulative satellite mass function of the MW, N-s(>= m(*)), down to the mass of the Fornax dwarf is within the 1 sigma distribution of all the MW-sized galaxies. We find that MW-sized hosts with three satellites more massive than Sgr (as the MW) are among the most common cases. However, the most and second most massive satellites in these systems are smaller than the LMC and SMC by roughly 0.7 and 0.8 dex, respectively. We conclude that the distribution N-s(>= m(*)) for MW-sized galaxies is quite broad, the particular case of the MW being of low frequency but not an outlier. The halo mass of MW-sized galaxies correlates only weakly with N-s(>= m(*)). Then, it is not possible to accurately determine the MW halo mass by means of its N-s(>= m(*)); from our catalog, we constrain a lower limit of 1.38 x 10(12) M-circle dot at the 1 sigma level. Our analysis strongly suggests that the abundance of massive subhalos should agree with the abundance of massive satellites in all MW-sized hosts, i.e., there is not a missing (massive) satellite problem for the Lambda CDM cosmology. However, we confirm that the maximum circular velocity, v(max), of the subhalos of satellites smaller than m(*) similar to 10(8) M-circle dot is systematically larger than the v(max) inferred from current observational studies of the MW bright dwarf satellites; different from previous works, this conclusion is based on an analysis of the overall population of MW-sized galaxies. Some pieces of evidence suggest that the issue could refer only to satellite dwarfs but not to central dwarfs, then environmental processes associated with dwarfs inside host halos combined with supernova-driven core expansion should be on the basis of the lowering of v(max).