HI and Star Formation Properties of Massive Galaxies: First Results from the GALEX Arecibo SDSS Survey

TL;DR

The GASS project studies cold gas in massive galaxies using HI observations from Arecibo, revealing how gas content relates to galaxy structure and color, with initial data showing diverse galaxy behaviors.

Contribution

First results from GASS provide new insights into HI properties of massive galaxies, establishing scaling relations and identifying unusual galaxy outliers.

Findings

HI gas fraction correlates with galaxy structure and color.

Identified gas-rich red sequence galaxies and gas-poor blue spirals.

Established a relation between gas fraction, stellar surface density, and NUV-r color.

Abstract

The GALEX Arecibo SDSS Survey (GASS) is an ambitious program designed to investigate the cold gas properties of massive galaxies, a challenging population for HI studies. Using the Arecibo radio telescope, GASS is gathering high-quality HI-line spectra for an unbiased sample of ~1000 galaxies with stellar masses greater than 10^10 Msun and redshifts 0.025 < z < 0.05, uniformly selected from the SDSS spectroscopic and GALEX imaging surveys. The galaxies are observed until detected or until a low gas mass fraction limit (1.5-5%) is reached. We present initial results based on the first Data Release, which consists of ~20% of the final GASS sample. We use this data set to explore the main scaling relations of HI gas fraction with galaxy structure and NUV-r colour, and show our best fit plane describing the relation between gas fraction, stellar mass surface density and NUV-r colour. Interesting outliers from this plane include gas-rich red sequence galaxies that may be in the process of regrowing their disks, as well as blue, but gas-poor spirals.