Star formation and gas inflows in the OH megamaser galaxy IRAS03056+2034

Abstract

We have obtained observations of the OH megamaser galaxy IRAS03056+2034 using the Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Very Large Array (VLA), and Hubble Space Telescope (HST). The HST data reveals spiral arms containing knots of emission associated with star-forming regions. The GMOS-IFU data cover the spectral range of 4500–7500 Å at a velocity resolution of 90 km s−1 and spatial resolution of 506 pc. The emission-line flux distributions reveal a ring of star-forming regions with radius of 786 pc centred at the nucleus of the galaxy, with an ionized gas mass of 2.1 × 105M , an ionizing photon luminosity of log Q[H+] = 53.3, and a star formation rate of 1.4 M yr−1. The emission-line ratios and radio emission suggest that the gas at the nuclear region is excited by both starburst activity and an active galactic nucleus. The gas velocity fields are partially reproduced by rotation in the galactic plane, but show, in addition, excess redshifts to the east of the nucleus, consistent with gas inflows towards the nucleus, with velocity of ∼45 km s−1 and a mass inflow rate of ∼2.2 × 10−3 M yr−1.