bluuebunny/crossref_metadata_2025_split huggingface dataset:
The intrinsic equatorial ellipticity of bulges
Authors: Méndez-Abreu J. , Aguerri J. A. L. , Corsini E. M. , Simonneau E. 
Published: July 2008

AbstractTraditionally, the study of the structural parameters of galaxies have been used to understand the bulge formation processes. However, one piece lost in this study is the three-dimensional shape of the bulges. In this work, the structural parameters of a magnitude-limited sample of 148 unbarred S0-Sb galaxies were derived to study the correlations between bulge and disk parameters as well as the probability distribution function (PDF) of the intrinsic equatorial ellipticity of bulges. A new algorithm (GASP-2D) was used to perform the bidimensional bulge-disk decomposition of J-band galaxy images extracted from the archive of the 2MASS survey. The PDF of intrinsic ellipticities was derived from the distribution of the observed ellipticities of bulges and misalignments between bulges and disks. About 80% of bulges in S0-Sb galaxies are not oblate but triaxial ellipsoids. Their mean axial ratio in the equatorial plane is 〈B/A〉=0.85. There is not significant dependence of their PDF on morphology, light concentration, and luminosity. The scenarios in which bulges assembled from mergers and/or grew over long times through disk secular evolution have to be tested against the derived PDF of bulge intrinsic ellipticities.
Observations across nearby spiral bulges
Authors: Sansom A. E. , Loubser S. I. , Sánchez-Blázquez P. , Söchting I. K. 
Published: July 2008

AbstractThe bulges of spiral galaxies may be old, as in our Galaxy, or may possess younger stars, as evidenced in spectroscopic line strengths in some external bulges. Bulges look similar to elliptical galaxies, but their formation history is expected to differ due to the presence of the disc and different formation mechanisms. This project extends the numbers of high signal-to-noise, broad coverage spectra to a larger sample of bulges in order to test conflicting ideas about their age distributions. New Gemini long-slit observations will be used to derive stellar population ages and histories across 30 bulges. Here we present preliminary results from the sample.
Gaseous flows in galaxies
Authors: Combes Francoise 
Published: July 2008

AbstractThe gas component plays a major role in the dynamics of spiral galaxies, because of its dissipative character, and its ability to exchange angular momentum with stars in the disk. Due to its small velocity dispersion, it triggers gravitational instabilities, and the corresponding non-axisymmetric patterns produce gravity torques, which mediate these angular momentum exchanges. When a srong bar pattern develops with the same pattern speed all over the disk, only gas inside corotation can flow towards the center. But strong bars are not long lived in presence of gas, and multiple-speed spiral patterns can develop between bar phases, and help the galaxy to accrete external gas flowing from cosmic filaments. The gas is then intermittently driven to the galaxy center, to form nuclear starbursts and fuel an active nucleus. The various time-scales of these gaseous flows are described.
Central mass accumulation in nuclear spirals
Authors: Maciejewski Witold 
Published: July 2008

AbstractIn central regions of non-axisymmetric galaxies high-resolution hydrodynamical simulations indicate spiral shocks, which are capable of transporting gas inwards. The efficiency of transport is lower at smaller radii, therefore instead of all gas dropping onto the galactic centre, a roughly uniform distribution of high-density gas develops in the gaseous nuclear spiral downstream from the shock, and the shear in gas is very low there. These are excellent conditions for star formation. This mechanism is likely to contribute to the process of (pseudo-) bulge formation.
12CO(J=3→2) detections in bulges of low surface brightness galaxies with APEX
Authors: Galaz Gaspar , Cortes Paulo , Bronfman Leonardo , Rubio Monica 
Published: July 2008

AbstractUsing the APEX sub-millimeter telescope we have detected for the first time the CO rotational transition 12CO(J=3→2) in two of five low surface brightness galaxies. For galaxies with positive detection, the emission is detected in their bulges, with measured gas velocity dispersion of about 80 km/s and observed main-beam brightness temperature TM B ~ 10 mK. Using a standard CO to H2 conversion factor, we are able to estimate molecular gas masses for LSBs with positive detections, and upper limits for those LSBs with negative detections. Assuming a higher gas temperature for the generation of the 12CO(J=3→2) line compared to that for the 12CO(J=1→0) one, results suggest that a warm molecular gas component is present in bulges, indicating a radiation field preventing the formation of large cooler amounts of molecular gas, compared to high surface brightness galaxies with higher metallicity and likely more dust.
The structure of early-type galaxies from the ACS Virgo and Fornax cluster surveys: cores, nuclei and supermassive black holes
Authors: Ferrarese Laura , Côté Patrick 
Published: July 2008

AbstractThe core structure of early-type galaxies is revisited in light of recent results from the ACS Virgo and Fornax Cluster Surveys. These surveys are comprised of HST/ACS g, z band images for a representative sample of 143 early-type galaxies, spanning a factor 720 in B-band luminosity. The data indicates a clear transition in the core structure going from the brightest to the faintest galaxies. In contrast to previous claims, however, this transition is found to be a continuous function of galaxy magnitude. We characterize the core structure in terms of deviations of the observed surface brightness profile – measured within ~ 2% of the galaxy effective radius – relative to the inner extrapolation of the Sérsic law that best fits the profiles on larger scales. Virtually all galaxies fainter than MB ~ −20 mag contain distinct stellar nuclei, and are described by surface brightness profiles that lie above the Sérsic extrapolation, while the reverse is true for brighter galaxies. The latter are also known to host supermassive black holes. A relation between SBHs and stellar nuclei is suggested by the fact that both types of “central massive objects” contain the same fraction, 0.2% of the total mass of the host galaxy.
The (quite dark) stellar cluster around the supermassive black hole Sagittarius A* at the center of the Milky Way
Authors: Schödel Rainer , Eckart A. 
Published: July 2008

AbstractHigh-resolution seeing limited and adaptive optics near-infrared imaging observations of the stellar cluster within about one parsec of the massive black hole Sagittarius A* allow us to obtain a detailed picture of the structure of the nuclear star cluster of the Milky Way. We find that the stellar number counts and the diffuse light of the unresolved stellar population can be described very well by a stellar density function in the form of a broken-power law. This agrees well with theoretical predictions on the structure of a dynamically relaxed star cluster around a massive black hole. However, the cusp slope is found to be too shallow, which may be related to mixing of different stellar populations and continuous star formation, phenomena that are not taken into account by current theory. Mass densities larger than 107 solar masses per pc3 are reached within 0.1 pc of the central black hole. Intriguingly, up to several tens of percent of the total cluster mass in the central parsec may be in the form of dark stellar remnants.
Dynamics of galactic nuclei: mass segregation and collisions
Authors: Freitag Marc , Dale James E. , Church Ross P. , Davies Melvyn B. 
Published: July 2008

AbstractMassive black holes (MBHs) with a mass below ~ 107 M⊙ are likely to reside at the centre of dense stellar nuclei shaped by 2-body relaxation, close interactions with the MBH and direct collisions. In this contribution, we stress the role of mass segregation of stellar-mass black holes into the innermost tenths of a parsec and point to the importance of hydrodynamical collisions between stars. At the Galactic centre, collisions must affect giant stars and some of the S-stars.
Supermassive black holes from OASIS and SAURON integral-field kinematics
Authors: Cappellari Michele , Bacon R. , Davies Roger L. , de Zeeuw P. T. , Emsellem Eric , Falcón-Barroso Jesús , Krajnović Davor , Kuntschner Harald , McDermid Richard M. , Peletier Reynier F. , Sarzi Marc , van den Bosch Remco C. E. , van de Ven Glenn 
Published: July 2008

AbstractSupermassive black holes are a key element in our understanding of how galaxies form. Most of the progress in this very active field of research is based on just ~30 determination of black hole masses, accumulated over the past decade. We illustrate how integral-field spectroscopy, and in particular our OASIS modeling effort can help improve the current situation.
Chemical evolution of Seyfert galaxies
Authors: Ballero Silvia K. , Matteucci Francesca , Ciotti Luca 
Published: July 2008

AbstractWe computed the chemical evolution of Seyfert galaxies, residing in spiral bulges, based on an updated model for the Milky Way bulge with updated calculations of the Galactic potential and of the feedback from the central supermassive black hole (BH) in a spherical approximation. We followed the evolution of bulges of masses 2 × 109 − 1011M⊙ by scaling the star-formation efficiency and the bulge scalelenght as in the inverse-wind scenario for ellipticals. We successfully reproduced the observed relation between the BH mass and that of the host bulge, and the observed peak nuclear bolometric luminosity. The observed metal overabundances are easily achieved, as well as the constancy of chemical abundances with the redshift.
Upper limits on the mass of supermassive black holes from STIS archival data
Authors: Beifiori A. , Corsini E. M. , Bontà E. Dalla , Pizzella A. , Coccato L. , Sarzi M. , Bertola F. 
Published: July 2008

AbstractThe growth of supermassive black holes (SMBHs) appears to be closely linked with the formation of spheroids. There is a pressing need to acquire better statistics on SMBH masses, since the existing samples are preferentially weighted toward early-type galaxies with very massive SMBHs. With this motivation we started a project aimed at measuring upper limits on the mass of the SMBHs that can be present in the center of all the nearby galaxies (D < 100 Mpc) for which STIS/G750M spectra are available in the HST archive. These upper limits will be derived by modeling the central emission-line widths ([N II] λλ6548, 6583, Hα and [S II] λλ6716, 6731) observed over an aperture of ~01 (R < 50 pc). Here we present our preliminary results for a subsample of 76 bulges.
A general relativistic model of galaxy bulges in GEDi paradigm
Authors: Coimbra-Araújo C. H. , Letelier P. S. 
Published: July 2008

AbstractRecently a new approach was presented where astronomical objects as galaxies and clusters are idealized as self-gravitating systems living in a universe endowed with more than 3+1 dimensions. A such paradigm, named GEDi (Gravitation with Extra Dimensions), may solve exactly the missing mass problem for rotation curves of galaxies or gravitational lensing of clusters with no dark matter particles. Here we present an introductory discussion about the construction of a real galaxy using a Miyamoto-Nagai solution for isotropical coordinates to mimic spiral galaxies with bulges.
Central black hole mass determination for blazars
Authors: Fan J. H. , Yuan Y. H. , Huang Y. , Gao Y. , Hua T. X. , Liu Y. 
Published: July 2008

AbstractIn this paper, we used the method to determine the central black mass (M), and the boosting factor (δ), the propagation angle (Φ), and the distance along the axis to the site of the γ-ray production (d) as well for 32 γ-ray loud blazars with available variability timescales. If we take the intrinsic γ-ray luminosity to be λ times the Eddington luminosity, i.e. $L_{\gamma}^{in}=\lambda{L_{\hbox{\it \scriptsize Edd}}}$, then we have following results: the masses of the black hole are in the range of (0.9 ~ 101)×107M⊙(λ = 1.0) or (1.30 ~ 153)×107M⊙(λ=0.1).
Feeding black holes: tracing gas flows from the outskirts to the centers of galaxies
Authors: Haan S. , Schinnerer E. , Mundell C. G. , Combes F. , García-Burillo S. , Emsellem E. 
Published: July 2008

AbstractWe analyzed the distribution and kinematics of the atomic gas (HI) in 16 nearby spiral galaxies. Our results indicate that the morphology of the atomic gas and dynamically disturbed outer disks correlate with the AGN type present (Seyfert, LINER). From the combined HI and CO data (from the NUGA project), 2-dimensional maps of the gas flow are computed and gas inflow rates are derived as a function of radius within the disks.
Radio variability properties for sources at multi-frequencies
Authors: Liu Y. , Fan J. H. , Wang H. G. 
Published: July 2008

AbstractUsing three radio databases of the university of Michigan Radio Astronomy Observatory (UMRAO), the National Radio Astronomy Observatory (NRAO), and the Metsähovi Observatory, we analyzed the radio light curves by the power spectral analysis and CLEANest method in search for possible periodicity. Multiple periods are found in some sources at multi-frequencies. We adopted the wavelets for period analysis of unevenly sampled time series to search for the evolution of the parameters (period, amplitude) of possible periodicities. Some possible variation of these parameters are found.
The black hole-dark matter halo connection
Authors: Sabra Bassem M. , Akl Maya Abi , Chahine Gilbert 
Published: July 2008

AbstractWe explore the connection between the central supermassive blackholes (SMBH) in galaxies and the dark matter halo through the relation between the masses of the SMBHs and the maximum circular velocities of their host galaxies, as well as the relationship between stellar velocity dispersion of the spheroidal component and the circular velocity. We rely on a heterogeneous sample containing galaxies of all types. The only requirement is that the galaxy has direct measurements of its SMBH mass, MBH, circular velocity, vc, and velocity dispersion, σ. We present a direct observational MBH − vc relation.
Mass outflow constraints in active nuclei and quasars from X-ray spectroscopy
Authors: Yaqoob Tahir 
Published: July 2008

AbstractAbsorption in the X-ray spectra of active galactic nuclei from outflowing gas can be modeled to yield critical physical information on the outflows. The outflow rate of mass ejected back into the ISM of the host galaxy and the resulting feedback could potentially have an impact on evolution. We give a brief overview of the current observational constraints on the outflows that should be taken into account by models of evolution and feedback.
Rejuvenation of spiral bulges
Authors: Thomas Daniel , Davies Roger L. 
Published: July 2008

AbstractWe seek to understand whether the stellar populations of galactic bulges show evidence of secular evolution triggered by the presence of the disc. To this end we re-analyse the sample of Proctor & Sansom (2002), deriving stellar population ages and element abundances from absorption line indices as functions of central velocity dispersion and Hubble type. In agreement with other studies in the literature, we find that bulges have relatively low luminosity weighted ages, the lowest age derived being 1.3 Gyr. Hence bulges are not generally old, but actually rejuvenated systems. We discuss evidence that this might be true also for the bulge of the Milky Way. The smallest bulges are the youngest with the lowest α/Fe ratios indicating the presence of significant star formation events involving 10 − 30 per cent of their total mass in the past 1 − 2 Gyr. No significant correlations of the stellar population parameters with Hubble Type are found. We show that the above relationships with σ coincide perfectly with those of early-type galaxies. At a given velocity dispersion, bulges and elliptical galaxies are indistinguishable as far as their stellar populations are concerned. These results favour an inside-out formation scenario and indicate that the discs in spiral galaxies of Hubble types Sbc and earlier cannot have a significant influence on the evolution of the stellar populations in the bulge component. The phenomenon of pseudobulge formation must be restricted to spirals of types later than Sbc.
The secular evolution of M83 central bulge
Authors: Dottori H. , Diaz R. J. , Agüero M. P. , Mast D. , Rodrigues I. 
Published: July 2008

AbstractThe luminosity profile of M 83 bulge can be traced by a de Vaucouleurs' law between ≈ 200 pc and ≈ 800 pc. The inner part can be fitted by a n = −1/2 Sérsic profile. Also the IR (J − K) color shows difference between the periphery and the central part of the bulge, both properties indicating the presence of a pseudobulge. Previous Gemini-S 3-D, Paβ spectroscopy of the central ≈ 5″×13″ revealed spider like diagrams indicating disk like motion around three extended masses identified respectively with the optical nucleus (ON), with the center of the bulge isophotes, similar to the CO kinematical center (KC), and with a condensation hidden at optical wavelengths (HN), coincident with the largest lobe in 10 μm emission, most probably a cannibalized satellite. Numerical simulations show that they suffer strong evaporation and they would merge engulfing also the star forming arc in few hundred Myr, increasing the mass at the kinematical center by a factor o five or more. Upper mass limit of putative Black Holes associated to ON, KC and HN are a few ten thousand to a million solar masses. GMOS+Gemini imaging and spectroscopy of a chain of radio sources has yield no optical high redshift counterparts. This radio sources are aligned with ON, neither associated to SN nor to HII regions and might point to an older similar phenomenon, which left behind a kick-off spur.
Stellar populations in late-type spirals observed with SAURON
Authors: Ganda Katia , Peletier Reynier F. , Falcón-Barroso Jesús , McDermid Richard M. 
Published: July 2008

AbstractWe present results on the stellar populations of a sample of 18 late-type spirals, based on data acquired with the integral-field spectrograph SAURON at the WHT. We present the two-dimensional line-strength maps, the central line indices, and estimate the star formation time-scale. In an exponentially declining SFR scenario, we find a trend between the time-scale τ and the central velocity dispersion: more massive galaxies show shorter burst durations. A detailed study on these data is published by Ganda et al. (2007).
Correlations between the age structure in early-type galaxies and their properties
Authors: Hempel Maren 
Published: July 2008

AbstractWe present the results on our investigation of the age structure in early-type galaxies, based on optical/near-infrared photometry. First results have shown that the age structure in early-type galaxies is not as uniform as previously thought. The conclusion can only be that the formation of these galaxies is not exclussively based on a single scenario, e.g. monolithic collapse, or hierarchical merging. In our galaxy survey we compare the age structure of galaxies in different galaxy environment, of different mass and with different integral light properties, using the globular cluster systems as stellar probes. Depending on the size of the globular cluster sample we derive a cumulative age distribution and compare it to simulated systems with a known age structure. This allows us to detect globular cluster sub-populations with an age difference of several Gyr. So far we have found two galaxies, members of small groups of galaxies, which contain a significant population of intermediate age globular clusters in the inner region of the galaxy.
Nature of bulges in the Hubble sequence
Authors: Laurikainen Eija , Salo H. , Buta R. , Knapen J. H. 
Published: July 2008

AbstractWe evaluate the nature of bulges in the Hubble sequence, based on an analysis of 216 disk galaxies of all morphological types (S0-Sd). For this purpose we collect our various analysis made separately for early and late-type galaxies, published in a series of papers. Using the criteria by Kormendy & Kennicutt we find strong evidence of pseudobulges in all Hubble types, including S0s. However, due to the relatively massive bulges in S0-S0/a galaxies it is not probable that the (pseudo)bulges in these galaxies were formed in a similar manner as in spirals. More likely, pseudobulges particularly in strongly barred early-type disk galaxies are suggested to be a combination of star formation and the nearly exponential central components of bars.
Kinematics of the dwarf elliptical galaxy IC 225
Authors: Miller Bryan W. , Rudie Gwen 
Published: July 2008

AbstractWe present the 2D kinematics of the nuclear region of the double-nucleated low-luminosity elliptical galaxy IC 225. Observations with the GMOS-N IFU at Gemini Observatory show a large amount of metal-rich gas coincident with the off-center nucleus. However, preliminary kinematics analysis indicates that the velocity of the stars in the off-center nucleus is distinct from that of the gas at the same position. Therefore, this is an intriguing example of how the formation of a nucleus or bulge may be occurring in a low-luminosity elliptical galaxy.
Abundance patterns in stars in the bulge and Galactic center
Authors: Cunha Katia , Smith V. V. , Sellgren K. , Blum R. D. , Ramírez S. V. , Terndrup D. M. 
Published: July 2008

AbstractWe discuss oxygen and iron abundance patterns in K and M red-giant members of the Galactic bulge and in the young and massive M-type stars inhabiting the very center of the Milky Way. The abundance results from the different bulge studies in the literature, both in the optical and the infrared, indicate that the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Based on these elevated values of [O/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a rapid chemical enrichment with perhaps a top-heavy initial mass function. The Galactic Center stars reveal a nearly uniform and slightly elevated (relative to solar) iron abundance for a studied sample which is composed of 10 red giants and supergiants. Perhaps of more significance is the fact that the young Galactic Center M-type stars show abundance patterns that are reminiscent of those observed for the bulge population and contain enhanced abundance ratios of α-elements relative to either the Sun or Milky Way disk at near-solar metallicities.
3-D kinematics in low foreground extinction windows of the Galactic bulge
Authors: Soto M. , Kuijken K. , Rich R. M. 
Published: July 2008

AbstractWe report the progress in our measurement of the 3-D kinematics in several low foreground extinction windows of the Galactic Bulge. In order to complete the 3-D kinematics of as many stars as possible, proper motions and radial velocities have been obtained using HST WFPC2-ACS and VLT VIMOS respectively. Our preliminary results for fields close to the galactic minor axis show a significant vertex deviation, which can be directly related to a signature of triaxility. This is one of the strongest proofs to date of the presence of the stellar bar in the galactic bulge.