Environmental Effects on the ISM and Star Formation Properties of Nearby Spiral Galaxies

Abstract We studied molecular gas properties in a sample of 98 H i - flux selected spiral galaxies within ~ 25 Mpc using the CO J = 3 − 2 line, observed with the JCMT, and subdivided into isolated, group, and Virgo subsamples. We find a larger mean H 2 mass in the Virgo galaxies compared to group galaxies, despite their lower mean H i mass. Combining our data with complementary Hα star formation rate measurements, Virgo galaxies have a longer molecular gas depletion times compared to group galaxies, perhaps due to heating processes in the cluster environment or differences in the turbulent pressure.