VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies III: the atlas of the stellar and ionized gas distribution

摘要

LIRGs and ULIRGs are much more numerous at higher redshifts than locally,dominating the star-formation rate density at redshifts ~1 - 2. Therefore, theyare important objects in order to understand how galaxies form and evolvethrough cosmic time. We aim to characterize the morphologies of the stellarcontinuum and the ionized gas (H_alpha) emissions from local sources, andinvestigate how they relate with the dynamical status and IR-luminosity of thesources. We use optical (5250 -- 7450 \AA) integral field spectroscopic (IFS)data for a sample of 38 sources, taken with the VIMOS instrument, on the VLT.We present an atlas of IFS images of continuum emission, H_alpha emission, andH_alpha equivalent widths for the sample. The H_alpha images frequently revealextended structures that are not visible in the continuum, such as HII regionsin spiral arms, tidal tails, rings, of up to few kpc from the nuclear regions.The morphologies of the continuum and H_alpha images are studied on the basisof the C_{2kpc} parameter, which measures the concentration of the emissionwithin the central 2 kpc. The C_{2kpc} values found for the H_alpha images arehigher than those of the continuum for the majority (85%) of the objects in oursample. On the other hand, most of the objects in our sample (~62%) have morethan half of their H_alpha emission outside the central 2 kpc. No clear trendsare found between the values of C_{2kpc} and the IR-luminosity of the sources.On the other hand, our results suggest that the star formation in advancemergers and early-stage interactions is more concentrated than in isolatedobjects. We compared the H_alpha and infrared emissions as tracers of thestar-formation activity. We find that the star-formation rates derived usingthe H_alpha luminosities generally underpredict those derived using the IRluminosities, even after accounting for reddening effects.