bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Dynamics in AGN Galaxies: First Results of the HI-NUGA Survey
Authors: Haan S. , Schinnerer E. , Mundell C.G. , García-Burillo S. , Combes F. 
Published: April 2007

AbstractThe process of fueling Active Galactic Nuclei (AGN) in galaxies is commonly associated with gas aggregation onto a central supermassive black hole. Up to now a general picture of the AGN fueling is missing: What mechanisms are responsible for the various kinds of AGNs? How to remove angular momentum from the material far away from the gravitational influence of the central black hole? Over the last decade observations have been pointing towards a hierarchy of mechanisms that all combine to transport the gas from the large kpc scales down to the inner pc scales. In addition, fueling mechanisms excited by the galactic environment, e.g. through minor mergers and tidal interactions, have been suggested.In order to study the gas transport from the outskirts of galaxies to the central AGN, we have embarked on a key project, NUGA (Nuclei of Galaxies): a high spectral and angular resolution CO and HI survey of low luminosity AGN in nearby galaxies (i.e. Seyferts, LINERs and transition objects).For our detailed HI study, 16 nearby AGN galaxies were observed in their 21 cm line emission of neutral HI gas using the NRAO Very Large Array (VLA) interferometer in its C- and D-array configuration (~20'' angular and ~5.2 km s−1 spectral resolution). The spiral galaxies in our sample range in Hubble type from Sa to Sbc. For all galaxies high quality mm-interferometric CO data as well as optical/NIR imaging data are available.Here, we present first results on the atomic gas distribution and kinematics in these galaxies: The HI gas properties are analyzed and then compared to the optical properties. Their HI morphology reveals a wide variety: rings, spiral arms, and central concentrated, where ring structures are mostly found in LINER hosts. The integrated surface brightness profiles show some significant differences between the HI gas and stellar light as well as their radial extent. Our analysis of the HI environment yields that 4 galaxies are surrounded by satellites and 8 galaxies have disturbed outer HI disks, probably due to ram pressure stripping and/or minor mergers. Our analysis of the HI kinematics provides rotation curves, dynamical masses and evidence for streaming motions for each galaxy.The inclusion of recently obtained VLA B-array data will provide ~7″ resolution for more than half of the sample. We will utilize gravity torques based on a definite phase shift between the gravitational potential and the HI gas distribution to determine the gas inflow, and thus the efficiency for feeding the central black hole. Further, the combined CO+HI+NIR/opt data will allow us to develop dynamical models describing the gas flow in galactic disks from the large kpc scales down to the inner pc scales for selected galaxies in our sample.
Rotation of Galaxy Dark Matter Halos
Authors: Herbert-Fort Stéphane , Zaritsky Dennis , Kim Yeun Jin , Bailin Jeremy , Taylor James E. 
Published: April 2007

AbstractThe degree to which outer dark matter halos of spiral galaxies rotate with the disk is sensitive to their accretion history and may be probed with associated satellite galaxies. We use the Steward Observatory Bok telescope to measure the sense of rotation of nearby isolated spirals and combine these data with those of their associated satellites (drawn from SDSS) to directly test predictions from numerical simulations. We aim to constrain models of galaxy formation by measuring the projected component of the halo angular momentum that is aligned with that of spiral galaxy disks, Jz. We find the mean bulk rotation of the ensemble satellite system to be co-rotating with the disk with a velocity of 22 ± 13 km/s, in general agreement with previous observational studies and suggesting that galaxy disks could be formed by halo baryons collapsing by a factor of ≈10. We also find a prograde satellite fraction of 51% and Jz, of the satellite system to be positively correlated with the disk, albeit at low significance (2655 ± 2232 kpc km/s).
Near Infrared Survey of the Nuclear Regions of the Milky Way
Authors: Joshi U. C. , Ganesh S. , Baliyan K. S. , Glass I. S. , Nagata T. 
Published: April 2007

AbstractResults based on the deep imaging survey of the inner region (~300pc of the bulge within |ℓ| ~ 1.5°, |b| ~ 0.5°) of the Milky Way are reported in this communication. This survey is about 2.5 magnitude deeper than DENIS and 2MASS and is able to detect stars of the red clump at a distance of the Galactic center. Toward some directions we find extinction reaching AV = 50 mag. A catalog of the sources is in preparation.
An Evolutionary Disc Model of NGC 5907
Authors: Just Andreas , Möllenhoff C. , Borch A. 
Published: April 2007

AbstractWe present the first physical disc model of NGC 5907, which reproduces simultaneouly the multi-band photometry in U, B, V, R, and I- band (Just et al., 2006, A&A in press, astro-ph/0608196). The model is based on the star formation history and dynamical evolution of the disc and includes dust extinction consistent with the dust properties derived from FIR observations. We also find naturally the stellar light eccess of the young sub-population near the midplane (hidden by the dust), which is required to heat the dust.
Globular Clusters in NGC 5128: The IMACS survey
Authors: Gómez M. , Geisler D. , Harris W. E. , Harris G. L. H. , Woodley K. A. 
Published: April 2007

AbstractTo extend our recent study of structural parameters of Globular Clusters (GCs) in the giant elliptical NGC 5128 (Gómez et al. 2006), we have obtained new high resolution images with the Magellan 6.5m at Las Campanas Observatory and the IMACS camera. Our images cover an area of 1.2 × 1.2 sq. degrees and have a seeing between 0.4 and 0.7'', thus making it possible to resolve a significant fraction of the GC population, which is now virtually entirely observed given the large spatial and magnitude range.Convolution techniques allow us to find and to study the cluster candidates using the stellar PSF and analytical profiles for their light distribution. We therefore are able to derive structural parameters like size (effective and core radii), ellipticity, position angle and concentration. This is combined with the extensive database in the Washington photometric system by Harris et al. (2004) to select clusters according to shape, extendedness and Washington magnitudes and colours, which has proven very useful in discriminating GCs from foreground stars and background galaxies and for deriving metallicities.Our first results for the central field (15'×15’) indicate that the GCs populate a large range of (MV, rh) parameter space, with typical sizes of Galactic GCs as well as much larger. Combined with our previous data, we find a continuum of clusters in this diagram, with no clear distinction between a variety of different ‘types’ often referred to, such as UCDs, Faint Fuzzies, etc.In addition, a large fraction of GCs show a significant ellipticity whereas a paucity of round clusters is observed. We also confirm with a large (~250) sample that metal-rich clusters are smaller than metal-poor ones, which is in keeping with the general trend found in other galaxies. (e.g. Jordán et al. 2005)
The Build-up of the Colour-Magnitude Relation
Authors: Tanaka Masayuki , Kodama Tadayuki 
Published: April 2007

AbstractWe discuss the build-up of the colour-magnitude relation. The colour-magnitude relation first appears at the bright end and the faint end appears later. Interestingly, the build-up of colour-magnitude relation is delayed in low density environments. We suggest that galaxies follow the environment-dependent down-sizing evolution.
Dark Matter in NGC 2974
Authors: Weijmans A. , Krajnović D. , Oosterloo T. A. , Morganti R. , de Zeeuw P. T. 
Published: April 2007

AbstractWe present HI observations of the elliptical galaxy NGC 2974, obtained with the VLA. These observations reveal that the previously detected HI disc in this galaxy (Kim et al. 1988) is in fact a ring. Combining the flat rotation curve with the central kinematics of the ionised gas, obtained with the integral-field spectrograph SAURON, allows us to determine the mass-to-light ratio M/L as a function of radius, ranging from 100 pc in the centre to 10 kpc at the edges of the HI ring. A dark halo is required to explain the observed rotation: at the outer radii ~70% of the total mass is dark†.
The Red Halos of Galaxies
Authors: Zackrisson Erik , Bergvall Nils , Östlin Göran , Micheva Genoveva , Caldwell Brady 
Published: April 2007

AbstractOptical and near-IR surface photometry of the halos of disk galaxies and blue compact galaxies have revealed a very red spectral energy distribution, which cannot easily be reconciled with any normal type of stellar population. Using spectral evolutionary models, we demonstrate that a stellar population with an extremely bottom-heavy initial mass function can explain the red halos of both types of objects. Because of its very high mass-to-light ratio, this halo population may account for some of the missing baryons in the local Universe.
Compact and Fossil Groups
Authors: de Oliveira Claudia Mendes , Amram Philippe 
Published: April 2007

AbstractWe present a short review on poor groups of galaxies focusing on the evolution of compact groups and formation of fossil groups. Fossil groups are systems with one dominant luminous elliptical galaxy surrounded by faint companions, in an extended X-ray halo. We will briefly discuss the possibility of fossil groups being the end-products of the merging of compact groups.
The ORELSE Survey
Authors: Gal Roy , Lubin L. M. , Squires G. K. 
Published: April 2007

AbstractThe ORELSE Survey (Observations of Redshift Evolution in Large Scale Environments) is a multi-wavelength program to study the large-scale structure around a sample of 20z>0.6 clusters, with the goal of understanding transformative processes affecting galaxies in a broad range of environments. The survey includes (1) deep optical imaging to map structure around the clusters; (2) optical spectroscopy to confirm redshifts, map the galaxy distribution, obtain cluster masses via dynamical estimates, and measure spectral properties; (3) ground-based K-band imaging, to better constrain galaxy stellar masses and improve photometric redshift estimates; (4) near-IR spectroscopy to study post-starburst galaxies and AGN; (5) HST imaging to obtain galaxy morphologies; (6) Spitzer IRAC and MIPS imaging to separate starburst and AGN populations, and examine dusty galaxies; and (7) Chandra and VLA mapping to find X-ray and radio-loud AGN that are not evident from optical data. We discuss here the motivation and some early results.
Formation and Evolution of Nucleated Galaxies
Authors: Bekki Kenji 
Published: April 2007

AbstractWe discuss how stellar galactic nuclei (SGN) form and evolve during galaxy formation and evolution based on chemodynamical simulations on the central regions (1-1000 pc) of galaxies. Our simulations demonstrate that dissipative formation of SGN through rapid transfer of gas into the central 10 pc of galaxies is more consistent with recent observations of SGN than dissipationless formation of SGN through merging of globular clusters (GCs). Nuclear structures in the remnants of major galaxy mergers between low-mass, nucleated spirals are found to depend strongly on the mass-ratio of massive black holes (MBHs) to SGN in spirals in the sense that the remnants have more distinct SGN in the mergers with the smaller MBH-to-SGN-mass-ratios. During the destruction of low-mass, nucleated galaxies by strong tidal fields of giant galaxies, SGN can remain intact. The stripped SGN can be observed as bright GCs around the giant galaxies. The color-magnitude relation of metal-poor GCs (referred to as “the blue tilt”) recently discovered for bright galaxies is similar to that of SGN, which suggests that the origin of the blue tilt is closely associated with the formation processes of SGN of gas-rich, low-mass dwarfs in the high redshift universe.
Infrared Properties of Nearby Interacting Galaxies: from Spirals to ULIRGs
Authors: Charmandaris Vassilis 
Published: April 2007

AbstractI present a brief review of some of the mid-infrared properties of interacting galaxies as these were revealed using observations from the Infrared Space Observatory and Spitzer Space Telescope over the last decade. The variation of the infrared spectral energy distribution in interacting galaxies can be used as an extinction free tracer not only of the location of the star formation activity but also of the physical mechanism dominating their energy production.‡.
Secular Evolution and the Morphological Transformation of Cluster and Field Galaxies
Authors: Zhang Xiaolei , Buta Ronald J. 
Published: April 2007

AbstractDeep surveys conducted during the past decades have shown that galaxies in the distant universe are generally of more irregular shapes, and are disky in appearance and in their star formation rate, compared to galaxies in similar environments in the nearby universe. Given that the merger rate between z= 2 and the local universe is far from adequate to account for this observed morphological transformation rate, an internal mechanism for the morphological transformation of galaxies is to be sought, whose operation can be further aided by environmental factors. The secular evolution mechanism, especially with the discovery of a collisionless dissipation mechanism for stars within the secular evolution paradigm, has provided just such a framework for understanding the morphological evolution of galaxies across the Hubble time. In this paper we will summarize the past theoretical results on the dynamical mechanisms for secular evolution, and highlight new results in the analysis of the observational data, which confirmed that density waves in physical galaxies possess the kind of characteristics which could produce theáobserved rates of morphological transformation for both cluster and field galaxies.
Enviromental Effects on Internal Color Gradients of Early-Type Galaxies
Authors: La Barbera F. , de Carvalho R.R. , Gal R.R. , Busarello G. , Haines C.P. , Mercurio A. , Merluzzi P. , Capaccioli M. , Djorgovski S.G. 
Published: April 2007

AbstractWe use g and r band imaging from the Palomar Abell Cluster Survey (Gal et al. 2000, AJ 120, 540) in order to estimate internal color gradients, measured as the logarithmic slope of galaxy radial color profiles, for a sample of 4000 early-type galaxies in N = 162 Abell clusters, spanning a wide richness range, from poor groups to rich clusters, and a redshift range of z=0.05 to z=0.25. Color gradients are estimated from the galaxy structural parameters (namely, the effective radius, re, and the Sersic index, n) in the g and r bands. These parameters are derived by fitting galaxy images with 2D PSF convolved Sersic models (La Barbera et al. 2002, ApJ, 571, 790). We select as early-type cluster galaxies those objects with Sersic index n>2, that lie on the color magnitude relation of each cluster. Only objects with S/N ratio high enough to derive reliable structural parameters are included in the analysis (La Barbera et al. 2005, ApJL, 626, 19). Field contamination amounts to ~10%; in our sample and is corrected for by using 32 blank fields observed with the same setup and analyzed in the same way as the cluster images. We find that color gradients follow two distinct redshift trends, with color gradients being less steep for richer rather than poor clusters (La Barbera et al. 2005, ApJL, 626, 19). Fig. 1 plots the mean internal color gradient of galaxies as a function of local galaxy density, which is estimated by using the Voronoi tessellation method. We find that color gradients are strongly dependent on local environment, with color gradients being less steep in higher rather than in lower density regions. However, this environmental trend only holds for poor clusters, with galaxies in rich clusters not showing any significant trend. These results support a picture whereby some interaction mechanism, such as galaxy-galaxy merging, flattens the internal color gradient of galaxies, producing the observed correlation with local density in low richness clusters. If rich clusters form through the merging of groups of galaxies, this process would wash out any correlation between local density and the past merging history of galaxies.
Extended HI Rotation Curve of M31 using deep DRAO observations
Authors: Carignan C. , Chemin L. , Foster T. 
Published: April 2007

AbstractCarignan et al. (C06, 2006, ApJ, 641, L109) recently presented an extended HI rotation curve (RC) of M31, using single dish observations from the 100m Effelsberg and Green Bank telescopes. These data were obtained along the semi-major axis of the approaching half of the M31 HI disk and showed a flat RC at large radius, which extends up to ~35 kpc (using D = 780 kpc). The kinematical analysis of M31 is pursued here and new deep 21cm observations obtained at the Dominion Radio Astrophysical Observatory (DRAO) are presented. A tilted-ring model is fitted to a new HI velocity field, allowing the derivation of the position angle P.A. and inclination i as a function of radius. We concentrate on the approaching half of the disk in order to compare our new results with those from C06. It is shown that the disk warping of M31 does not severely contaminate the kinematics of the neutral gas. As a consequence, the RC from C06 is in very good agreement with the new derived RC.
The Strong Transformation of Spiral Galaxies Infalling into Massive Clusters at z~ 0.2
Authors: Cortese L. , Marcillac D. , Richard J. , Bravo-Alfaro H. , Kneib J.-P. , Rieke G. , Covone G. , Egami E. , Rigby J. , Czoske O. , Davies J. 
Published: April 2007

AbstractWe report the discovery of two peculiar galaxies infalling into the lensing clusters of galaxies Abell 1689 (z~ 0.18) and 2667 (z~ 0.23). Hubble Space Telescope images show extraordinary trails composed by blue bright knots and stellar streams associated with both these systems, an ~L* and ~0.1L* galaxy. Under the combined action of tidal interaction with the cluster potential and of ram pressure by the intra-cluster medium the morphologies and star formation histories of these two galaxies are strongly perturbed. While in the massive system tidal interactions are the dominant effect and are able to produce a sinking of gas towards the galaxy center triggering a strong burst of star formation and changing galaxy's morphology, in the smaller galaxy the effects of gravitation are reduced by ram pressure stripping which blows away the neutral hydrogen from the galactic disk, quenching the star formation activity and transforming a gas rich late type spiral into quiescent disk dominated early type system. This result is a new additional evidence that galaxy mass represents the main driver of galaxy evolution, even during their dive into the harsh cluster environment and can give additional insights on the origin of S0s and dwarf cluster galaxies.
The Size-Luminosity Relation of Disk Galaxies in EDisCS Clusters
Authors: Gogarten Stephanie M. , Dalcanton Julianne J. , Simard Luc , Rudnick Gregory , Desai Vandana ,   the EDisCS Collaboration
Published: April 2007

AbstractWe present the size-luminosity relation (SLR) for disk galaxies observed in eight clusters from the ESO Distant Cluster Survey (EDisCS). These clusters, at redshifts 0.4 < z < 0.8, were observed with the Hubble Space Telescope's Advanced Camera for Surveys. While we observe a change in the SLR with redshift, namely that there is an absence of low surface brightness galaxies at high redshift, we demonstrate that this could be a product of selection effects and thus is not a confirmation of evolution. We also compare the SLR for cluster and field galaxies in each redshift bin and see no significant effects of environment on the SLR.
The Sunyaev-Zel'dovich Effect of Nearby Clusters in the 3-Year WMAP Data
Authors: Hu Jian , Nie Jianyin , Zhang Shuangnan 
Published: April 2007

AbstractWe explore the thermal Sunyaev-Zel'dovich (SZ) effect of a sample of 31 clusters in the three-year data of the Wilkinson Microwave Anisotropy Probe (WMAP), and detect strong SZ signal at the ~10 σ level. By comparing the co-added SZ profile of the sample clusters with the prediction based on the X-ray observations of ROSAT and XMM-Newton, we find the SZ profiles are consistent with the isothermal β-model of intracluster medium (ICM), but the central region (<0°.2) may be contaminated by the central radio sources in the clusters. We derive a mean outer radius of the ICM distribution at ~1.2 ± 0.4rvir (68% CL). The existence of the ICM outer edge could be the first evidence of ICM accretion shock, which is important for understanding the formation and evolution of clusters. We also estimate the mean gas mass fraction of the ICM from the overall amplitude of the SZ signals as fgas = 0.10 ± 0.05, which is consistent with the X-ray observation and lower than the cosmic average baryon fraction.
Planetary Nebulae as a Probe of the Local Group Galaxies Evolution
Authors: Kniazev A. Y. , Pustilnik S. A. , Grebel E. K. , Zucker D. B. , Vaisanen P. 
Published: April 2007

AbstractWe present the latest results from our study of PNe and HII regions in two Local Group dwarf irregular galaxies IC 10 and NGC 6822.
Luminosity Function of Galaxies in Substructures of Galaxy Clusters
Authors: Krywult Janusz 
Published: April 2007

AbstractThe analysis of the R-band luminosity function of galaxies in substructures of 21 Abell clusters shows that the characteristic magnitude M* for dominant substructure is brighter than in the second substructure and the magnitude gap between two brightest galaxies in dominant substructure is larger than in the second one.
Catalog of Positions and Spectroscopic Properties of Galaxies in the A1367 Cluster
Authors: Lipovka N. M. , Morales J. C. Saucedo , Lipovka A. A. , Boldycheva A. V. , Maslennikov K. L. 
Published: April 2007

AbstractIn the present work the results of an optical spectroscopy study of 8 galaxies projected in the central part of the A1367 cluster are reported. The observations were made using the 2.2 m. Guillermo Haro Telescope in Cananea (Mexico), and the Boller and Chivens spectrograph. A catalog of the optical positions of more than 100 galaxies in the cluster is presented. The redshifts of 7 galaxies were determined from their absorption systems, while for the remaining galaxy was obtained from its strong emission lines of H-alpha, S II, O III and H-beta. For one of the galaxies the emission redshift is z= 0.015, not showing absorptions lines at the cluster redshifts (z = 0.026), which argues that it is located between the observer and the A1367 cluster.