Ram-pressure stripping of the interstellar medium in NGC 4485

Abstract

This paper describes submm, 12CO (J = 2-1) observations of the interacting pair of galaxies NGC 4490 and 4485, and together with high resolution HI and multifrequency radio continuum data we investigate the evolution of the ISM in this system. We find the following. (i) The smaller member of the pair, NGC 4485, has had the atomic, molecular and dust components of its ISM stripped via ram pressure during its recent passage through the extended HI distribution of NGC 4490. A bow-shock is identified in the HI ahead of the stripped gas. (ii) Within the disc of NGC 4490 we find a very low H2-to-HI ratio as well as a strong correlation between thermal emission and mass of H2 suggesting that the star formation rate is limited in this case by the conversion of HI to H2. (iii) 12CO emission from an HI and radio-continuum bridge between the two galaxies is detected.