The JCMT Nearby Galaxies Legacy Survey - XI. Environmental variations in the atomic and molecular gas radial profiles of nearby spiral galaxies

We present an analysis of the radial profiles of a sample of 43 H I-flux selected spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) with resolved James Clerk Maxwell Telescope (JCMT) CO J = 3 - 2 and/or Very Large Array (VLA) H I maps. Comparing the Virgo and non-Virgo populations, we confirm that the H I discs are truncated in the Virgo sample, even for these relatively H I-rich galaxies. On the other hand, the H₂ distribution is enhanced for the Virgo galaxies near their centres, resulting in higher H₂ to H I ratios and steeper H₂ and total gas radial profiles. This is likely due to the effects of moderate ram pressure stripping in the cluster environment, which would preferentially remove low-density gas in the outskirts while enhancing higher density gas near the centre. Combined with Hα star formation rate data, we find that the star formation efficiency (SFR/H₂) is relatively constant with radius for both samples, but the Virgo galaxies have an ∼40 per cent lower star formation efficiency than the non-Virgo galaxies.