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

TL;DR

This study uses integral field spectroscopy to map the stellar and ionized gas structures in local luminous and ultraluminous infrared galaxies, revealing extended star-forming regions and analyzing their morphologies and star-formation activity.

Contribution

It provides a detailed atlas of IFS images of LIRGs and ULIRGs, analyzing their morphological properties and comparing star-formation tracers, which enhances understanding of galaxy evolution.

Findings

H_alpha images often show extended structures not visible in continuum.

Most objects have higher H_alpha concentration within 2 kpc but also significant emission outside this region.

Star-formation rates from H_alpha underpredict IR-based rates even after reddening correction.

Abstract

LIRGs and ULIRGs are much more numerous at higher redshifts than locally, dominating the star-formation rate density at redshifts ~1 - 2. Therefore, they are important objects in order to understand how galaxies form and evolve through cosmic time. We aim to characterize the morphologies of the stellar continuum and the ionized gas (H_alpha) emissions from local sources, and investigate how they relate with the dynamical status and IR-luminosity of the sources. 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, and H_alpha equivalent widths for the sample. The H_alpha images frequently reveal extended structures that are not visible in the continuum, such as HII regions in 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 basis of the C_{2kpc} parameter, which measures the concentration of the emission within the central 2 kpc. The C_{2kpc} values found for the H_alpha images are higher than those of the continuum for the majority (85%) of the objects in our sample. On the other hand, most of the objects in our sample (~62%) have more than half of their H_alpha emission outside the central 2 kpc. No clear trends are 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 advance mergers and early-stage interactions is more concentrated than in isolated objects. We compared the H_alpha and infrared emissions as tracers of the star-formation activity. We find that the star-formation rates derived using the H_alpha luminosities generally underpredict those derived using the IR luminosities, even after accounting for reddening effects.