Characterization of gas-rich galaxies from ALFALFA's survey data

Abstract

This research work is the first statistical study of the properties of the galaxies included in the final data release (A-100) of the Arecibo Legacy Fast ALFA survey (ALFALFA). The recently completed ALFALFA survey constitutes a representative sample of the nearby Universe in the 21 cm line of the neutral Hidrogen (HI), with more than 30 000 extragalactic sources out to z 0:06. Its substantial overlap with wide-area surveys conducted at other wavelengths has been used to create a consistent multi-wavelength catalog of parameters for galaxies within about 250 Mpc (800 million light-years) from us. We have characterized the gas-rich galaxies by comparing their content of atomic hydrogen with several properties from the optical window ranging from intrinsic luminosities and colors to estimators of the morphology and structure. Our results corroborate earlier findings that there does not appear to be a significant population of optically dark but HI-rich galaxies and that most HI-rich galaxies are very blue, while we find that their colors and HI masses are more strongly correlated than previously suspected. In addition, we have (not just confirmed but) found a clearer decrement of the bar fraction with increasing HI content, an anti-correlation that is not explained by known trends for more massive (stellar) and redder disc galaxies to host more bars and have lower gas contents