Gas Mass Fraction In Galaxies Research Articles

S2COSMOS: Evolution of gas mass with redshift using dust emission

ABSTRACT We investigate the evolution of the gas mass fraction for galaxies in the COSMOS field using submillimetre emission from dust at 850 μm. We use stacking methodologies on the 850 μm S2COSMOS map to derive the gas mass fraction of galaxies out to high redshifts, 0 ≤ z ≤ 5, for galaxies with stellar masses of $10^{9.5} \lt M_* (\rm M_{\odot }) \lt 10^{11.75}$. In comparison to previous literature studies we extend to higher redshifts, include more normal star-forming galaxies (on the main sequence), and also investigate the evolution of the gas mass fraction split by star-forming and passive galaxy populations. We find our stacking results broadly agree with scaling relations in the literature. We find tentative evidence for a peak in the gas mass fraction of galaxies at around z ∼ 2.5–3, just before the peak of the star formation history of the Universe. We find that passive galaxies are particularly devoid of gas, compared to the star-forming population. We find that even at high redshifts, high stellar mass galaxies still contain significant amounts of gas.

ALFALFA H I data stacking - III. Comparison of environmental trends in H I gas mass fraction and specific star formation rate

It is well known that both the star formation rate and the cold gas content of a galaxy depend on the local density out to distances of a few Megaparsecs. In this paper, we compare the environmental density dependence of the atomic gas mass fractions of nearby galaxies with the density dependence of their central and global specific star formation rates. We stack HI line spectra extracted from the Arecibo Legacy Fast ALFA survey centered on galaxies with UV imaging from GALEX and optical imaging/spectroscopy from SDSS. We use these stacked spectra to evaluate the mean atomic gas mass fraction of galaxies in bins of stellar mass and local density. For galaxies with stellar masses less than 10^10.5 M_sun, the decline in mean atomic gas mass fraction with density is stronger than the decline in mean global and central specific star formation rate. The same conclusion does not hold for more massive galaxies. We interpret our results as evidence for ram-pressure stripping of atomic gas from the outer disks of low mass satellite galaxies. We compare our results with the semi-analytic recipes of Guo et al. (2011) implemented on the Millennium II simulation. These models assume that only the diffuse gas surrounding satellite galaxies is stripped, a process that is often termed "strangulation". We show that these models predict relative trends in atomic gas and star formation that are in disagreement with observations. We use mock catalogues generated from the simulation to predict the halo masses of the HI-deficient galaxies in our sample. We conclude that ram-pressure stripping is likely to become effective in dark matter halos with masses greater than 10^13 M_sun.

Effects of metal enrichment and metal cooling in galaxy growth and cosmic star formation history

We present the results of a numerical study on the effects of metal enrichment and metal cooling on galaxy formation and cosmic star formation (SF) history using cosmological hydrodynamic simulations. We find following differences in the simulation with metal cooling when compared to the run without it: (1) the cosmic star formation rate (SFR) is enhanced by about 50 & 20% at z=1 & 3, respectively; (2) the gas mass fraction in galaxies is lower; (3) the total baryonic mass function (gas + star) at z=3 does not differ significantly, but shows an increase in the number of relatively massive galaxies at z=1; (4) the baryonic mass fraction of intergalactic medium (IGM) is reduced at z<3 due to more efficient cooling and gas accretion onto galaxies. Our results suggest that the metal cooling enhances the galaxy growth by two different mechanisms: (1) increase of SF efficiency in the local interstellar medium (ISM), and (2) increase of IGM accretion onto galaxies. The former process is effective throughout most of the cosmic history, while the latter is effective only at z<3 when the IGM is sufficiently enriched by metals owing to feedback.