Presentation #241.19 in the session Evolution of Galaxies — iPoster Session.
It is well known that the amount of cold gas in a galaxy is correlated with its star-formation rate, i.e. star-forming galaxies tend to host more gas. In addition, recent work has revealed tight correlations between star-formation rate and various structural parameters, notably the stellar surface mass density within the inner 1 kpc, Σ1. Since cold gas is necessary for star formation, one would also expect correlations to exist between gas content and galaxy structure. To test this, we explore a number of these morphological parameters — velocity dispersion, Sérsic index, global stellar mass surface density, and Σ1 — and their correlations with the molecular hydrogen (fH2) and atomic hydrogen (fHI) gas fractions. Our gas measurements are taken from the xCOLD GASS and ALFALFA surveys, yielding a sample of 227 galaxies with H2 detections and 3,535 galaxies with HI detections within a redshift range of 0.01 ≤ z ≤ 0.05 and a stellar mass range of 109 M☉ ≤ M* ≤ 1011.5 M☉. Structural parameters were obtained from publicly available catalogs based on Sloan Digital Sky Survey observations of these objects. By comparing Spearman correlation coefficients and analyzing the scatter in the data, we find that for both fHI and fH2, the strongest correlation is with Σ1. Using only Σ1, we can predict fHI to within a factor of 1.8 and fH2 to within a factor of 2.3. The larger residuals in the correlations involving H2 may be due to the limited availability of H2 measurements. Larger sample sizes would likely strengthen the correlation between fH2 and Σ1. Our findings highlight the predictive power of Σ1 and offer a method to estimate cold gas content using readily available parameters for large samples of galaxies.