392 research outputs found
The Arecibo Legacy Fast ALFA Survey: VI. Second HI Source Catalog of the Virgo Cluster Region
We present the third installment of HI sources extracted from the Arecibo
Legacy Fast ALFA extragalactic survey. This dataset continues the work of the
Virgo ALFALFA catalog. The catalogs and spectra published here consist of data
obtained during the 2005 and 2006 observing sessions of the survey. The catalog
consists of 578 HI detections within the range 11h 36m < R.A.(J2000) < 13h 52m
and +08 deg < Dec.(J2000) < +12 deg, and cz_sun < 18000 km/s. The catalog
entries are identified with optical counterparts where possible through the
examination of digitized optical images. The catalog detections can be
classified into three categories: (a) detections of high reliability with S/N >
6.5; (b) high velocity clouds in the Milky Way or its periphery; and (c)
signals of lower S/N which coincide spatially with an optical object and known
redshift. 75% of the sources are newly published HI detections. Of particular
note is a complex of HI clouds projected between M87 and M49 that do not
coincide with any optical counterparts. Candidate objects without optical
counterparts are few. The median redshift for this sample is 6500 km/s and the
cz distribution exhibits the local large scale structure consisting of Virgo
and the background void and the A1367-Coma supercluster regime at cz_sun ~7000
km/s. Position corrections for telescope pointing errors are applied to the
dataset by comparing ALFALFA continuum centroid with those cataloged in the
NRAO VLA Sky Survey. The uncorrected positional accuracy averages
27 arcsec ~(21 arcsec ~median) for all sources with S/N > 6.5 and is of order
~21 arcsec ~(16 arcsec ~median) for signals with S/N > 12. Uncertainties in
distances toward the Virgo cluster can affect the calculated HI mass
distribution.Comment: 25 pages, 1 Table, 8 figures, Accepted by the Astronomical Journa
Catalog of Galaxy Morphology in Four Rich Clusters: Luminosity Evolution of Disk Galaxies at 0.33<z<0.83
Hubble Space Telescope (HST) imaging of four rich, X-ray luminous, galaxy
clusters (0.33<z<0.83) is used to produce quantitative morphological
measurements for galaxies in their fields. Catalogs of these measurements are
presented for 1642 galaxies brighter than F814W(AB)=23.0 . Galaxy luminosity
profiles are fitted with three models: exponential disk, de Vaucouleurs bulge,
and a disk-plus-bulge hybrid model. The best fit is selected and produces a
quantitative assessment of the morphology of each galaxy: the principal
parameters derived being B/T, the ratio of bulge to total luminosity, the scale
lengths and half-light radii, axial ratios, position angles and surface
brightnesses of each component. Cluster membership is determined using a
statistical correction for field galaxy contamination, and a mass normalization
factor (mass within boundaries of the observed fields) is derived for each
cluster. In the present paper, this catalog of measurements is used to
investigate the luminosity evolution of disk galaxies in the rich-cluster
environment. Examination of the relations between disk scale-length and central
surface brightness suggests, under the assumption that these clusters represent
a family who share a common evolutionary history and are simply observed at
different ages, that there is a dramatic change in the properties of the small
disks (h < 2 kpc). This change is best characterized as a change in surface
brightness by about 1.5 magnitude between z=0.3 and z=0.8 with brighter disks
at higher redshifts.Comment: 53 pages, including 13 figures and 7 tables. Accepted for publication
in the Astrophysical Journal Supplement Serie
The GALEX Arecibo SDSS Survey. VI. Second Data Release and Updated Gas Fraction Scaling Relations
We present the second data release from the GALEX Arecibo SDSS Survey (GASS),
an ongoing large Arecibo program to measure the HI properties for an unbiased
sample of ~1000 galaxies with stellar masses greater than 10^10 Msun and
redshifts 0.025<z<0.05. GASS targets are selected from the Sloan Digital Sky
Survey (SDSS) spectroscopic and Galaxy Evolution Explorer (GALEX) imaging
surveys, and are observed until detected or until a gas mass fraction limit of
a few per cent is reached. This second data installment includes new Arecibo
observations of 240 galaxies, and marks the 50% of the complete survey. We
present catalogs of the HI, optical and ultraviolet parameters for these
galaxies, and their HI-line profiles. Having more than doubled the size of the
sample since the first data release, we also revisit the main scaling relations
of the HI mass fraction with galaxy stellar mass, stellar mass surface density,
concentration index, and NUV-r color, as well as the gas fraction plane
introduced in our earlier work.Comment: 30 pages, 12 figures. Accepted for publication in A&A. Version with
complete Appendix A available at http://www.mpa-garching.mpg.de/GASS/pubs.php
. GASS released data can be found at
http://www.mpa-garching.mpg.de/GASS/data.ph
Galaxy morphology in the rich cluster Abell 2390
We have analysed images of the field of A2390 obtained with the CFHT and HST.
The analysis fits models to bulge and disk components to several hundred
galaxies, with about equal samples from the cluster and field. We also have
assessed and graded asymmetries in the images. The cluster galaxies are
compared in different cluster locations and also compared with field galaxies.
We find that the central old population galaxies are bulge-dominated, while
disk systems have young populations and are found predominantly in the outer
cluster. S0 and bulgy disk galaxies are found throughout, but concentrate in
regions of substructure. Disks of cluster blue galaxies are generally brighter
and smaller than those in the field. We find that the cluster members have a
higher proportion of interacting galaxies than the field sample. Interactions
in the cluster and in the field, as well as cluster infall, appear to inhibit
star-formation in galaxies.Comment: 20 pages including 10 of tables, plus 7 figures; To appear in the
Astronomical Jorurna
COLD GASS, an IRAM Legacy Survey of Molecular Gas in Massive Galaxies: III. Comparison with semi-analytic models of galaxy formation
We compare the semi-analytic models of galaxy formation of Fu et al. (2010),
which track the evolution of the radial profiles of atomic and molecular gas in
galaxies, with gas fraction scaling relations derived from the COLD GASS survey
(Saintonge et al 2011). The models provide a good description of how condensed
baryons in galaxies with gas are partitioned into stars, atomic and molecular
gas as a function of galaxy stellar mass and surface density. The models do not
reproduce the tight observed relation between stellar surface density and
bulge-to-disk ratio for this population. We then turn to an analysis of
the"quenched" population of galaxies without detectable cold gas. The current
implementation of radio-mode feedback in the models disagrees strongly with the
data. In the models, gas cooling shuts down in nearly all galaxies in dark
matter halos above a mass of 10**12 M_sun. As a result, stellar mass is the
observable that best predicts whether a galaxy has little or no neutral gas. In
contrast, our data show that quenching is largely independent of stellar mass.
Instead, there are clear thresholds in bulge-to-disk ratio and in stellar
surface density that demarcate the location of quenched galaxies. We propose
that processes associated with bulge formation play a key role in depleting the
neutral gas in galaxies and that further gas accretion is suppressed following
the formation of the bulge, even in dark matter halos of low mass.Comment: 12 figures, accepted for publication in MNRAS, the COLD GASS data is
available at http://www.mpa-garching.mpg.de/COLD_GASS/data.shtm
xGASS: gas-rich central galaxies in small groups and their connections to cosmic web gas feeding
We use deep HâI observations obtained as part of the extended GALEX Arecibo SDSS survey (xGASS) to study the cold gas properties of central galaxies across environments. We find that below stellar masses of 1010.2 Mâ, central galaxies in groups have an average atomic hydrogen gas fraction âŒ0.3 dex higher than those in isolation at the same stellar mass. At these stellar masses, group central galaxies are usually found in small groups of N = 2 members. The higher HâI content in these low-mass group central galaxies is mirrored by their higher average star formation activity and molecular hydrogen content. At larger stellar masses, this difference disappears and central galaxies in groups have similar (or even smaller) gas reservoirs and star formation activity compared to those in isolation. We discuss possible scenarios able to explain our findings and suggest that the higher gas content in low-mass group central galaxies is likely due to the contributions from the cosmic web or HâI-rich minor mergers, which also fuel their enhanced star formation activity
The Far-Infrared, UV and Molecular Gas Relation in Galaxies up to z=2.5
We use the infrared excess (IRX) FIR/UV luminosity ratio to study the
relation between the effective UV attenuation (A_IRX) and the UV spectral slope
(beta) in a sample of 450 1<z<2.5 galaxies. The FIR data is from very deep
Herschel observations in the GOODS fields that allow us to detect galaxies with
SFRs typical of galaxies with log(M)>9.3. Thus, we are able to study galaxies
on and even below the main SFR-stellar mass relation (main sequence). We find
that main sequence galaxies form a tight sequence in the IRX--beta plane, which
has a flatter slope than commonly used relations. This slope favors a SMC-like
UV extinction curve, though the interpretation is model dependent. The scatter
in the IRX-beta plane, correlates with the position of the galaxies in the
SFR-M plane. Using a smaller sample of galaxies with CO gas masses, we study
the relation between the UV attenuation and the molecular gas content. We find
a very tight relation between the scatter in the IRX-beta plane and the
specific attenuation (S_A), a quantity that represents the attenuation
contributed by the molecular gas mass per young star. S_A is sensitive to both
the geometrical arrangement of stars and dust, and to the compactness of the
star forming regions. We use this empirical relation to derive a method for
estimating molecular gas masses using only widely available integrated
rest-frame UV and FIR photometry. The method produces gas masses with an
accuracy between 0.12-0.16 dex in samples of normal galaxies between z~0 and
z~1.5. Major mergers and sub-millimeter galaxies follow a different S_A
relation.Comment: 11 pages, 6 pages appendix, 11 figures, accepted to Ap
Geometrical tests of cosmological models. III. The cosmology-evolution diagram at z=1
The rotational velocity of distant galaxies, when interpreted as a size
(luminosity) indicator, may be used as a tool to select high redshift standard
rods (candles) and probe world models and galaxy evolution via the classical
angular diameter-redshift or Hubble diagram tests. We implement the proposed
testing strategy using a sample of 30 rotators spanning the redshift range
0.2<z<1 with high resolution spectra and images obtained by the VIMOS/VLT Deep
Redshift Survey (VVDS) and the Great Observatories Origins Deep Survey (GOODs).
We show that by applying at the same time the angular diameter-redshift and
Hubble diagrams to the same sample of objects (i.e. velocity selected galactic
discs) one can derive a characteristic chart, the cosmology-evolution diagram,
mapping the relation between global cosmological parameters and local
structural parameters of discs such as size and luminosity. This chart allows
to put constraints on cosmological parameters when general prior information
about discs evolution is available. In particular, by assuming that equally
rotating large discs cannot be less luminous at z=1 than at present (M(z=1) <
M(0)), we find that a flat matter dominated cosmology (Omega_m=1) is excluded
at a confidence level of 2sigma and an open cosmology with low mass density
(Omega_m = 0.3) and no dark energy contribution is excluded at a confidence
level greater than 1 sigma. Inversely, by assuming prior knowledge about the
cosmological model, the cosmology-evolution diagram can be used to gain useful
insights about the redshift evolution of the structural parameters of baryonic
discs hosted in dark matter halos of nearly equal masses.Comment: 14 pages and 11 figures. A&A in pres
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