24 research outputs found
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
The effect of the environment on the HI scaling relations
We use a volume-, magnitude-limited sample of nearby galaxies to investigate
the effect of the environment on the HI scaling relations. We confirm that the
HI-to-stellar mass ratio anti correlates with stellar mass, stellar mass
surface density and NUV-r colour across the whole range of parameters covered
by our sample (10^9 <M*<10^11 Msol, 7.5 <mu*<9.5 Msol kpc^-2, 2<NUV-r<6 mag).
These scaling relations are also followed by galaxies in the Virgo cluster,
although they are significantly offset towards lower gas content.
Interestingly, the difference between field and cluster galaxies gradually
decreases moving towards massive, bulge-dominated systems. By comparing our
data with the predictions of chemo-spectrophotometric models of galaxy
evolution, we show that starvation alone cannot explain the low gas content of
Virgo spirals and that only ram-pressure stripping is able to reproduce our
findings. Finally, motivated by previous studies, we investigate the use of a
plane obtained from the relations between the HI-to-stellar mass ratio, stellar
mass surface density and NUV-r colour as a proxy for the HI deficiency
parameter. We show that the distance from the `HI gas fraction plane' can be
used as an alternative estimate for the HI deficiency, but only if carefully
calibrated on pre-defined samples of `unperturbed' systems.Comment: Accepted for publication on MNRAS main journal. 11 pages, 6 figures,
1 tabl
HI content and other structural properties of galaxies in the Virgo cluster from the Arecibo Legacy Fast ALFA Survey
We report the results of an HI blind survey of 80deg^2 of the Virgo cluster,
based on the 08deg < delta < 16 deg strip of ALFALFA, the Arecibo Legacy Fast
ALFA Survey. 187 HI sources of high significance are found providing a complete
census of HI sources in this region of the Virgo cluster (-1000<cz<3000 km/s)
with M_HI > 10^7.5-8 M_sun. 156/187 (83%) sources are identified with optical
galaxies from the Virgo Cluster Catalogue (Binggeli et al. 1985), all but 8
with late-type galaxies. Ten sources are not associated with optical galaxies
and were found to correspond to tidally-disrupted systems (see Kent et al. 2007
and Haynes, Giovanelli and Kent 2007). The remaining 21 (11%) are associated
with galaxies that are not listed in the Virgo Cluster Catalogue. For all
sources with an optical counterpart in the Sloan Digital Sky Survey, we
analyzed i-band SDSS plates to measure optical structural parameters. We find
that in the Virgo cluster: i) HI inhabits galaxies that are structurally
similar to ordinary late-type galaxies; ii) their HI content can be predicted
from their optical luminosity; iii) low surface brightness galaxies have low
optical luminosity and contain small quantities of neutral hydrogen; iv) low
surface brightness, massive Malin1 type galaxies are comfortably rare objects
(less than 0.5%); v) there are no "dark-galaxies" with HI masses M_HI >
10^7.5-8 M_sun; vi) less than 1% of early-type galaxies contain neutral
hydrogen with M_HI>10^7.5-8 M_sun (di Serego Alighieri et al. 2007).Comment: 10 pages, 10 Postscript figures, accepted for publication in
Astronomy and Astrophysics (25/01/2008) - Replaced to fit A&A vers. 6.
Halpha3: Halpha imaging survey of HI selected galaxies from ALFALFA
We present Halpha3 (acronym for Halpha-alpha-alpha), an Halpha narrow-band
imaging survey of ~400 galaxies selected from the HI Arecibo Legacy Fast ALFA
Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster. By
using hydrogen recombination lines as a tracer of recent star formation, we aim
to investigate the relationships between atomic neutral gas and newly formed
stars in different environments (cluster and field), morphological types
(spirals and dwarfs), and over a wide range of stellar masses (~10^7.5-10^11.5
Msun). We image in Halpha+[NII] all the galaxies that contain more than 10^7
Msun of neutral atomic hydrogen in the sky region 11^h < R.A. <16^h 4^o < Dec.
<16^o; 350< cz <2000 km/s using the San Pedro Martir 2m telescope. This survey
provides a complete census of the star formation in HI rich galaxies of the
local universe. We present the properties of the galaxy sample, together with
Halpha fluxes and equivalent widths. We find an excellent agreement between the
fluxes determined from our images in apertures of 3 arcsec diameter and the
fluxes derived from the SDSS spectral database. From the Halpha fluxes
corrected for galactic and internal extinction and for [NII] contamination we
derive the global star formation rates (SFRs).Comment: 22 pages, 8 figures. A&A accepted. Atlas available upon reques
The dust scaling relations of the Herschel Reference Survey
We combine new Herschel/SPIRE sub-millimeter observations with existing
multiwavelength data to investigate the dust scaling relations of the Herschel
Reference Survey, a magnitude-, volume-limited sample of ~300 nearby galaxies
in different environments. We show that the dust-to-stellar mass ratio
anti-correlates with stellar mass, stellar mass surface density and NUV-r
colour across the whole range of parameters covered by our sample. Moreover,
the dust-to-stellar mass ratio decreases significantly when moving from late-
to early-type galaxies. These scaling relations are similar to those observed
for the HI gas-fraction, supporting the idea that the cold dust is tightly
coupled to the cold atomic gas component in the interstellar medium. We also
find a weak increase of the dust-to-HI mass ratio with stellar mass and colour
but no trend is seen with stellar mass surface density. By comparing galaxies
in different environments we show that, although these scaling relations are
followed by both cluster and field galaxies, HI-deficient systems have, at
fixed stellar mass, stellar mass surface density and morphological type
systematically lower dust-to-stellar mass and higher dust-to-HI mass ratios
than HI-normal/field galaxies. This provides clear evidence that dust is
removed from the star-forming disk of cluster galaxies but the effect of the
environment is less strong than what is observed in the case of the HI disk.
Such effects naturally arise if the dust disk is less extended than the HI and
follows more closely the distribution of the molecular gas phase, i.e., if the
dust-to-atomic gas ratio monotonically decreases with distance from the
galactic center.Comment: 18 pages, 15 figures, 2 tables. Accepted for publication on A&