bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulating the dynamics of binary black holes in nuclear gaseous discs
Authors: Dotti Massimo , Colpi Monica , Haardt Francesco , Mayer Lucio 
Published: July 2008

AbstractWe study the pairing of massive black holes embedded in a massive circum–nuclear, rotationally supported disc, until they form a close binary. Using high resolution SPH simulations, we follow the black hole dynamics, and in particular the eccentricity evolution, as a function of the composition in stars and gas of the disc. Binary–disc interaction always leads to orbital decay and, in case of co–rotating black holes, to orbit circularization. We present also a higher resolution simulation performed using the particle–splitting technique showing that the binary orbital decay is efficient down to a separation of ~ 0.1 pc, comparable to our new resolution limit. We detail the gaseous mass profile bound to each black hole. Double nuclear activity is expected to occur on an estimated timescale of ≲ 10 Myrs.
Brightness temperature for radio sources
Authors: Fan J. H. , Huang Y. , Liu Y. , Gao Y. , Hua T. X. , Yang J. H. 
Published: July 2008

AbstractIn this work, using the database of the university of Michigan Radio Astronomy Observatory (UMRAO), we determined the brightness temperatures, TB for a sample of 167 radio sources. The value of TB is in a range of log TB(K) = 10.46 to 20.08, which suggested that the boosting factors are in a range of δ = 0.41 to 41.26.
12CO observations on narrow-line Seyfert 1 galaxies
Authors: Kawaguchi Toshihiro , Nakanishi K. , Kohno K. , Ohta K. , Aoki K. 
Published: July 2008

AbstractIn order to investigate how the growth of galactic bulges is accompanied with the growth of central black holes (BHs), we observed molecular gas (fuel for the coming star formation) in possibly young active galaxies, narrow-line Seyfert 1 galaxies (NLS1s). We present the results of pilot observations of 12CO (1→0) line using the Nobeyama Millimeter Array for two FIR-bright NLS1s, ending in the first detection of their CO emission. Corresponding molecular-gas masses M(H2) of (1−3)×109M⊙ are the 2nd and 4th largest ones among NLS1s. Together with CO data for other NLS1s (including our sub-kpc observations) and for broad-line Seyfert 1 galaxies (BLS1s), we found that NLS1s and BLS1s contain a similar amount of molecular–gas. We do not see a significant difference in M(H2)/MBH ratios and in M(H2)/Mbulge ratios between NLS1s and BLS1s. The lack of a clear difference in M(H2) between them indicates either that bulge and BH growth phases are not overlapped or that the duration of star formation is much longer than that of active galaxies.
Black holes in low-mass bulges and pseudobulges
Authors: Nowak N. , Saglia R. P. , Thomas J. , Erwin P. , Bender R. 
Published: July 2008

AbstractOver the past decade we have learned that probably all ellipticals and bulges contain a central supermassive black hole (SMBH). The mass of the SMBH correlates both with the mass of the bulge component (about 0.15% of the bulge mass) and with the velocity dispersion σ of the bulge. We are investigating whether these relations remain valid or how they change when galaxies with pseudobulges, very low-mass bulges or bulgeless galaxies are considered. Studying SMBH relations for both classical bulges and pseudobulges can reveal the importance of different growing mechanisms (mergers vs. secular evolution) for the evolution of SMBHs. Low-mass classical bulges and bulgeless galaxies may harbour seed black holes in their earliest evolutionary stages, and studying them is of paramount importance for understanding the link between bulge evolution and black hole growth.
Gravitational loss-cone instability in stellar clusters around massive black holes
Authors: Polyachenko Evgeny V. , Polyachenko Valerij L. , Shukhman Ilia G. 
Published: July 2008

AbstractStability of spherical and thin disk stellar clusters surrounding massive black holes are studied. Due to the black hole, stars with sufficiently low angular momenta escape from the system through the loss cone. We show that stability of spherical clusters crucially depend on whether the distribution of stars is monotonic or non-monotonic in angular momentum. It turns out that only non-monotonic distributions can be unstable. At the same time the instability in disk clusters is possible for both types of distributions.
An accreting black hole in the nucleus of the bulgeless galaxy NGC 1042
Authors: Shields Joseph C. , Walcher Carl Jakob , Böker Torsten , Ho Luis C. , Rix Hans-Walter , van der Marel Roeland P. 
Published: July 2008

AbstractCompact star clusters are commonly found in the centers of galaxies and may foster formation of intermediate-mass “seed” black holes that facilitate the growth of supermassive black holes in galaxy nuclei. Such star clusters can be studied with minimal background starlight contamination in bulgeless galaxies. We present new results that point to the presence of an accreting black hole associated with the central star cluster in the Sd galaxy NGC 1042, and discuss implications for the bulge-black hole connection.
Massive galaxies with very young AGN
Authors: de Vries Nathan , Snellen I. A. G. , Schilizzi R. T. , Lehnert M. D. , Bremer M. N. 
Published: July 2008

AbstractGigahertz Peaked Spectrum (GPS) radio galaxies are generally thought to be the young counterparts of classical extended radio sources and live in massive ellipticals. GPS sources are vital for studying the early evolution of radio-loud AGN, the trigger of their nuclear activity, and the importance of feedback in galaxy evolution. We study the Parkes half-Jansky sample of GPS radio galaxies of which now all host galaxies have been identified and 80% has their redshifts determined (0.122 < z < 1.539). Analysis of the absolute magnitudes of the GPS host galaxies show that at z > 1 they are on average a magnitude fainter than classical 3C radio galaxies. This suggests that the AGN in young radio galaxies have not yet much influenced the overall properties of the host galaxy. However their restframe UV luminosities indicate that there is a low level of excess as compared to passive evolution models.
Spiral galaxies in the SAURON survey
Authors: Peletier Reynier F. , Ganda Katia , Falcón-Barroso Jesús , Bacon Roland , Cappellari Michele , Davies Roger L. , de Zeeuw P. Tim , Emsellem Eric , Krajnović Davor , Kuntschner Harald , McDermid Richard M. , Sarzi Marc , van de Ven Glenn 
Published: July 2008

AbstractWe discuss some recent integral field spectroscopy using the SAURON instrument of a sample consisting of 24 early-type spirals, part of the SAURON Survey, and 18 late-type spirals. Using 2-dimensional maps of their stellar radial velocity, velocity dispersion, and absorption line strength, it is now much easier to understand the nature of nearby galactic bulges. We discuss a few highlights of this work, and point out some new ideas about the formation of galactic bulges.
Age and metallicity of the bulges in lenticular galaxies
Authors: Sil'chenko Olga K. 
Published: July 2008

AbstractPanoramic spectroscopy of the sample of 80 nearby lenticular galaxies is presented. The SSP-equivalent ages, [Z/H], and [Mg/Fe] are determined through the Lick indices Hβ, Mgb, and 〈Fe〉 separately for the nuclei and for the bulges. About a half of the sample contain chemically distinct nuclei, more metal-rich and younger than the bulges. The statistics of stellar population properties for the nearby S0s is discussed.
The formation and evolution of bulges as traced by globular cluster systems
Authors: Forbes Duncan A. , Spitler Lee 
Published: July 2008

AbstractGlobular Clusters provide a unique method for tracing the formation and evolution of their host galaxies. As single stellar populations they are far easier to interpret than the multi-population complexity of galaxy field stars. The scaling properties of globular clusters provide important constraints on the hierarchical assembly history of galaxies. Here we briefly review recent progress using the Hubble Space Telescope for imaging and the Keck plus Gemini telescopes for spectroscopy. We argue that the red, or metal-rich, subpopulation of GCs is associated with the bulge/spheroid component of galaxies. As one of the oldest stellar systems available for study, we discuss how globular clusters can be used to constrain the formation of galaxy bulges, in particular the role of mergers vs secular evolution. We conclude that metal-rich GCs, and hence bulges, formed very early in the Universe with more recent mergers having a small effect at most.
Stellar populations in the center of barred spiral galaxies
Authors: Mollá M. , Cantin S. , Robert C. , Pellerin A. 
Published: July 2008

AbstractWe show observations obtained with the integral field spectrometer OASIS for the centers of a sample of barred galaxies. The high spatial resolution of the instrument allows to distinguish spatially some structures within these regions as defined by stellar populations of different ages and metallicities. From these data we deduce important clues about the star formation history. But we advise that, in order to obtain adequately the evolutionary sequence, a combination of chemical and synthesis models might be necessary.
Internal kinematics and stellar populations of early-type galaxies in the Fornax cluster
Authors: Gerken Bettina , Davies Roger L. , Kuntschner Harald 
Published: July 2008

AbstractWe present a study of the internal kinematics and stellar populations of early-type galaxies in the Fornax cluster. 10 galaxies in a luminosity range of −21.8≤MB≤−17.4 were observed with the integral field units (IFU) of Gemini South GMOS and VLT-VIMOS. Velocity maps and age-metallicity diagrams are presented for NGC 1404 and NGC 1419.
Stellar population in bulge of spiral galaxies
Authors: Morelli L. , Pompei E. , Pizzella A. , Coccato L. , Corsini E. M. , Abreu J. Méndez , Saglia R. P. , Sarzi M. , Bertola F. 
Published: July 2008

AbstractWe present extensive photometric and spectroscopic study to give a new insight in the bulge stellar population. Super-solar α/Fe and its constant value along the radial profile, in most of the galaxies, suggest that the star formation in these objects has been fast and occurred at the same time in the whole bulge.
The role of bars on bulge formation and the evolution of barred galaxies
Authors: Pérez I. , Sánchez-Blázquez P. , Zurita A. 
Published: July 2008

AbstractWe have started a long term project to analyse the role played by bars in bulge formation and the formation and evolution of bars from the point of view of their star formation histories and stellar populations. To this aim, we have obtained high S/N long slit spectra of 22 barred galaxies, ranging in morphological types between S0 to Sb galaxies. We have obtained Lick/IDS indices along the bar for all the sample galaxies. We used Vazdekis et al. (2007) models to derive simple stellar population ages and metallicities. Extreme care has been taken to correct the indices for any nebular contribution. Preliminary results show that the bulges of barred galaxies are similar to those of unbarred galaxies. The metalicity gradients along bars show a dependency with the central stellar velocity dispersion. The galaxies with higher central dispersion appear to have a gradient in both age and metallicity changing radially outward to a younger and more metal rich population. The galaxies with lower central velocity dispersion show a change in age and metallicity with respect to the inner part of the bar with the populations at the end of the bar being younger or same age and more metal poor. There is no correlation between the gradient and the morphological or nuclear type. There is no correlation either with the total K-band luminosity. The fact that we observe galaxies with the outer parts of the bar more metal rich than the inner parts shows that at least some bars are old, since it requires long time for the observed enrichment to take place. The gradients in these bars are opposite to what is generally found in disks. The correlation between the central velocity dispersion and the bar gradient relates both, the dynamical and stellar population aging of the bar.
The Galactic bulge: a review
Authors: Minniti Dante , Zoccali Manuela 
Published: July 2008

AbstractThe Milky Way is the only galaxy for which we can resolve individual stars at all evolutionary phases, from the Galactic center to the outskirt. The last decade, thanks to the advent of near IR detectors and 8 meter class telescopes, has seen a great progress in the understanding of the Milky Way central region: the bulge. Here we review the most recent results regarding the bulge structure, age, kinematics and chemical composition. These results have profound implications for the formation and evolution of the Milky Way and of galaxies in general. This paper provides a summary on our current understanding of the Milky Way bulge, intended mainly for workers on other fields.
Kinematics and composition of the Galactic bulge: recent progress
Authors: Rich R. Michael , Howard Christian , Reitzel David B. , Zhao HongSheng , de Propris Roberto 
Published: July 2008

AbstractWe present recent results from a Keck study of the composition of the Galactic bulge, as well as results from the bulge Bulge Radial Velocity Assay (BRAVA). Culminating a 10 year investigation, Fulbright, McWilliam, & Rich (2006, 2007) solved the problem of deriving the iron abundance in the Galactic bulge, and find enhanced alpha element abundances, consistent with the earlier work of McWilliam & Rich (1994). We also report on a radial velocity survey of 2MASS-selected M giant stars in the Galactic bulge, observed with the CTIO 4m Hydra multi-object spectrograph. This program is to test dynamical models of the bulge and to search for and map any dynamically cold substructure in the Galactic bulge. We show initial results on fields at −10° < l < + 10° and b = −4°. We construct a longitude-velocity plot for the bulge stars and the model data, and find that contrary to previous studies, the bulge does not rotate as a solid body; from −5° < l < + 5° the rotation curve has a slope of ≈ 100 km s−1 and flattens considerably at greater l and reaches a maximum rotation of 45 km s−1 (heliocentric) or ~ 70 km s−1 (Galactocentric). This rotation is slower than that predicted by the dynamical model of Zhao (1996).
The boxy bulge and stellar bar of the Milky Way
Authors: Mahoney T. J. , López-Corredoira M. , Cabrera-Lavers A. , Hammersley P. L. , González-Fernández C. , Garzón F. 
Published: July 2008

AbstractWe describe the boxy bulge, long stellar bar and elliptical ring of the Galaxy. This model has largely evolved from NIR survey work by many teams and differs from other models with a monolithic ellipsoidal bulge. We maintain that the structure of the inner Galaxy can only be properly studied by adequately sampling the entire Galactic plane for |l| < 30°, |b| < 1.5°, and that the bulge is best studied at least 3° from the plane. We briefly report a slight radially outwardly increasing metallicity gradient along the bar and reaffirm de Vaucouleurs & Pence's (1978) suggestion that the Galaxy is probably of morphological type SAB(rs)bc II.
Proper motions in the Galactic bulge: Plaut's window
Authors: Vieira Katherine , Cassetti-Dinescu Dana , Méndez René A. , Rich R. Michael , Girard Terrence M. , Korchagin Vladimir I. , van Altena William , Majewski Steven R. , van den Bergh Sidney 
Published: July 2008

AbstractA proper motion study of a field of 20′ × 20′ inside Plaut's low extinction window (l,b)=(0o, −8o), has been completed. Relative proper motions and photographicBVphotometry have been derived for ~ 21,000 stars reaching toV~ 20.5 mag, based on the astrometric reduction of 43 photographic plates, spanning over 21 years of epoch difference. Proper motion errors are typically 1 mas yr−1. Cross-referencing with the 2MASS catalog yielded a sample of ~ 8700 stars, from which predominantly disk and bulge subsamples were selected photometrically from theJHcolor-magnitude diagram. The two samples exhibited different proper-motion distributions, with the disk displaying the expected reflex solar motion. Galactic rotation was also detected for stars between ~2 and ~3 kpc from us. The bulge sample, represented by red giants, has an intrinsic proper motion dispersion of (σl, σb) = (3.39, 2.91)±(0.11, 0.09) mas yr−1, which is in good agreement with previous results. A mean distance of$6.37^{+0.87}_{-0.77}$kpc has been estimated for the bulge sample, based on the observedKmagnitude of the horizontal branch red clump. The metallicity [M/H] distribution was also obtained for a subsample of 60 bulge giants stars, based on calibrated photometric indices. The observed [M/H] shows a peak value at [M/H] ~ −0.1 with an extended metal poor tail and around 30% of the stars with supersolar metallicity. No change in proper motion dispersion was observed as a function of [M/H]. We are currently in the process of obtaining CCDUBV RIphotometry for the entire proper-motion sample of ~ 21,000 stars.
The Millennium Galaxy Catalogue: the severe attenuation of bulge flux by dusty spiral discs
Authors: Driver Simon P. ,   the MGC Team
Published: July 2008

AbstractUsing the Millennium Galaxy Catalogue we quantify the dependency of the disc and bulge luminosity functions on galaxy inclination. Using a contemporary dust model we show that our results are consistent with galaxy discs being optically thick in their central regions ($\tau_B^f=3.8\pm0.7$). As a consequence the measured B-band fluxes of bulges can be severely attenuated by 50% to 95% depending on disc inclination. We argue that a galaxy's optical appearance can be radically transformed by simply removing the dust, e.g. during cluster infall, with mid-type galaxies becoming earlier, redder, and more luminous. Finally we derive the mean photon escape fraction from the integrated galaxy population over the 0.1 μm to 2.1 μm range, and use this to show that the energy of starlight absorbed by dust (in our model) is in close agreement with the total far-IR emission.
Morphological properties of massive galaxies at high−z from GOODS
Authors: Ravindranath Swara , Daddi E. , Giavalisco M. , Ferguson H. C. , Dickinson M. E. 
Published: July 2008

AbstractWe have used the BzK-selection to identify a composite population of passive, and star-forming galaxies at redshifts 1.4 ≤ z ≤ 2.5 from the Great Observatories Origins Deep Survey (GOODS). Using an unprecedented large sample of galaxies in this redshift range, we characterize the morphological diversity through the analysis of the surface-brightness profile shapes for 171 galaxies with passive SEDs, and 1068 star-forming galaxies. We find that the z ~ 2 galaxies display a wide range of morphologies, from spheroidals to disk-like. Interestingly, the galaxies with passively-evolving SEDs predominantly have steep profiles as seen for the classical bulges at low redshifts, although they are very compact with re < 3 kpc. The star-forming galaxies on the other hand exhibit mostly disk-like and merger morphologies, and have sizes comparable to their low−z counterparts. Our results emphasize the need for an unbiased selection in order to reveal the morphological diversities, and range of galaxy properties at high redshifts.
VIRUS-W A fiber based integral field unit spectrograph for the study of galaxy bulges
Authors: Fabricius Maximilian H. , Bender Ralf , Drory Niv , Grupp Frank , Hill Gary J. , Hopp Ulrich 
Published: July 2008

AbstractWe presented the design for a fiber based integral field unit spectrograph for the new two meter class Wendelstein telescope in Bavaria, Germany. The proposed spectrograph will feature a fiberhead consisting of 246 individual optical fibers and a field of view of approximately 1′ × 2′ and two different spectral resolution modes optimized for the study of bulges of local late-type galaxies.
JASMINE – design and method of data reduction
Authors: Yamada Yoshiyuki , Gouda Naoteru , Yano Taihei , Kobayashi Yukiyasu , Niwa Yoshito ,   JASMINE Working Group
Published: July 2008

AbstractJapan Astrometry Satellite Mission for Infrared Exploration (JASMINE) aims to construct a map of the Galactic bulge with 10 μ arc sec accuracy. We use z-band CCD for avoiding dust absorption, and observe about 10 × 20 degrees area around the Galactic bulge region. Because the stellar density is very high, each FOVs can be combined with high accuracy. With 5 years observation, we will construct 10 μ arc sec accurate map.In this poster, I will show the observation strategy, design of JASMINE hardware, reduction scheme, and error budget. We also construct simulation software named JASMINE Simulator. We also show the simulation results and design of software.
Galaxy bulges at mid- and high-redshift
Authors: Conselice Christopher J. 
Published: July 2008

AbstractBulges are a major galaxy component in the nearby universe, and are one of the primary features that differentiates and defines galaxies. The origin of bulges can be directly probed in part by examining distant galaxies to search for high redshift bulges, and to study the properties of bulges in formation. We review the evidence for bulges at high redshift in this article, and how by studying bulges through a variety of approaches, including through morphological, colour, and stellar mass selection, we can determine when and how these systems assembled. We argue that the majority of the most massive ‘classical’ bulges are in place byz~ 1.5 − 2, and likely formed very early through major mergers. Other, likely lower mass, bulges form through a secular process along with their disks. Direct observations suggest that these two formation processes are occurring, as spheroids are commonly seen atz< 1, as are disks and spiral galaxies in the form of luminous diffuse objects, clump-clusters, and chain galaxies. However, bulge+disk systems are relatively rare untilz~ 1, suggesting that this structural assembly occurred relatively late.
The fundamental plane of bulges at intermediate redshift
Authors: MacArthur Lauren A. , Ellis Richard S. , Treu Tommaso 
Published: July 2008

AbstractWe report on a new study aimed at understanding the diversity and evolutionary properties of distant galactic bulges in the context of well-established trends for pure spheroidal galaxies. Bulges have been isolated for a sample of 137 spiral galaxies in the GOODS fields within the redshift range 0.1 < z < 1.2. Using proven photometric techniques we determine for each galaxy the characteristic parameters (size, surface brightness, profile shape) in the 4 GOODS-ACS imaging bands of both the disk and bulge components. Using the DEIMOS spectrograph on Keck, precision stellar velocity dispersions were secured for a sizeable fraction of the bulges. This has enabled us to compare the Fundamental Plane of our distant bulges with that of field spheroidal galaxies in a similar redshift range. Bulges in spiral galaxies with a bulge-to-total luminosity ratio (B/T) > 0.2 show very similar patterns of evolution to those seen for low luminosity spheroidals. To first order, their recent mass assembly histories are equivalent.
Keck laser guide star observations of 11 GOODS-South Chandra sources at z ~ 1
Authors: Ammons S. Mark , Melbourne Jason , Koo David C. , Max Claire E. 
Published: July 2008

AbstractThe Center for Adaptive Optics (CfAO) Treasury Survey (CATS) has observed 11 Chandra sources (10 AGN) at z ~ 1 in the GOODS-South field with the laser guide star adaptive optics (LGSAO) system at Keck Observatory. We combine this K band imaging with ACS imaging in the B, V, I, and z bands to obtain multi-color imaging at a spatial resolution better than 100 mas in all bands. We attempt to remove central optical point sources from AGN using the GALFIT (Peng et al. 2002) routine. We fit Bruzual & Charlot (2003) tau-models to the residuals and find young, dusty stellar populations in the central 1-2 kpc (the mean central optical depth at rest-frame 500 nm is 4-5).