Morphological classification of local luminous infrared galaxies

June 2016 • 2016A&A...591A...1P

Authors • Psychogyios, A. • Charmandaris, V. • Diaz-Santos, T. • Armus, L. • Haan, S. • Howell, J. • Le Floc'h, E. • Petty, S. M. • Evans, A. S.

Abstract • We present analysis of the morphological classification of 89 luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS) sample, using non-parametric coefficients and compare their morphology as a function of wavelength. We rely on images that were obtained in the optical (B- and I-band) as well as in the infrared (H-band and 5.8 μm). Our classification is based on the calculation of Gini and the second order of light (M₂₀) non-parametric coefficients, which we explore as a function of stellar mass (M_⋆), infrared luminosity (L_IR), and star formation rate (SFR). We investigate the relation between M₂₀, the specific SFR (sSFR) and the dust temperature (T_dust) in our galaxy sample. We find that M₂₀ is a better morphological tracer than Gini, as it allows us to distinguish systems that were formed by double systems from isolated and post-merger LIRGs. The effectiveness of M₂₀ as a morphological tracer increases with increasing wavelength, from the B to H band. In fact, the multi-wavelength analysis allows us to identify a region in the Gini-M₂₀ parameter space where ongoing mergers reside, regardless of the band used to calculate the coefficients. In particular, when measured in the H band, a region that can be used to identify ongoing mergers, with minimal contamination from LIRGs in other stages. We also find that, while the sSFR is positively correlated with M₂₀ when measured in the mid-infrared, I.e. star-bursting galaxies show more compact emission, it is anti-correlated with the B-band-based M₂₀. We interpret this as the spatial decoupling between obscured and unobscured star formation, whereby the ultraviolet/optical size of an LIRG experience an intense dust-enshrouded central starburst that is larger that in the mid-infrared since the contrast between the nuclear to the extended disk emission is smaller in the mid-infrared. This has important implications for high redshift surveys of dusty sources, where sizes of galaxies are routinely measured in the rest-frame ultraviolet.

Links

• PREPRINT http://arxiv.org/abs/1602.08500
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2016A%26A...591A...1P
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/201628093/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F201628093
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2016A%26A...591A...1P
• PDF https://www.aanda.org/10.1051/0004-6361/201628093/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2016A%26A...591A...1P
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2016A%26A...591A...1P
• DATA https://irsa.ipac.caltech.edu/bibdata/2016/P/2016A&A...591A...1P.html