ALFALFA HI Data Stacking II. HI content of the host galaxies of AGN

Understand

We use a stacking technique to measure the average HI content of a volume-limited sample of 1871 AGN host galaxies from a parent sample of galaxies selected from the SDSS and GALEX imaging surveys with stellar masses greater than 10^10 M_sun and redshifts in the range 0.025<z<0.05.

• HI data are available from the Arecibo Legacy Fast ALFA (ALFALFA) survey.
• In previous work, we found that the HI gas fraction in galaxies correlates most strongly with the combination of optical/UV colour and stellar surface mass density.
• We therefore build a control sample of non-AGN matched to the AGN hosts in these two properties.