Kinematics of Arp 270: gas flows, nuclear activity and two regimes of star formation

Abstract

We have observed the Arp 270 system (NGC 3395 & NGC 3396) in H{\\alpha}\nemission using the GH{\\alpha}FaS Fabry-Perot spectrometer on the 4.2m William\nHerschel Telescope (La Palma). In NGC 3396, which is edge-on to us, we detect\ngas inflow towards the centre, and also axially confined opposed outflows,\ncharacteristic of galactic superwinds, and we go on to examine the possibility\nthat there is a shrouded AGN in the nucleus. The combination of surface\nbrightness, velocity and velocity dispersion information enabled us to measure\nthe radii, FWHM, and the masses of 108 HII regions in both galaxies. We find\ntwo distinct modes of physical behaviour, for high and lower luminosity\nregions. We note that the most luminous regions show especially high values for\ntheir velocity dispersions and hypothesize that these occur because the higher\nluminosity regions form from higher mass, gravitationally bound clouds while\nthose at lower luminosity HII regions form within molecular clouds of lower\nmass, which are pressure confined.\n