Morphology and Molecular Gas Fractions of Local Luminous Infrared Galaxies as a Function of Infrared Luminosity and Merger Stage
Abstract
We present a new, detailed analysis of the morphologies and molecular gas fractions (MGFs) for a complete sample of 65 local luminous infrared galaxies from Great Observatories All-Sky Luminous Infrared Galaxies (LIRG) Survey using high resolution I-band images from The Hubble Space Telescope, the University of Hawaii 2.2 m Telescope and the Pan-STARRS1 Survey. Our classification scheme includes single undisturbed galaxies, minor mergers, and major mergers, with the latter divided into five distinct stages from pre-first pericenter passage to final nuclear coalescence. We find that major mergers of molecular gas-rich spirals clearly play a major role for all sources with {L}{IR}\gt {10}11.5{L}⊙ ; however, below this luminosity threshold, minor mergers and secular processes dominate. Additionally, galaxies do not reach {L}{IR}\gt {10}12.0{L}⊙ until late in the merger process when both disks are near final coalescence. The mean MGF ({MGF} = {M}{{{H}}2}/({M}* +{M}{{{H}}2})) for non-interacting and early-stage major merger LIRGs is 18 ± 2%, which increases to 33 ± 3%, for intermediate stage major merger LIRGs, consistent with the hypothesis that, during the early-mid stages of major mergers, most of the initial large reservoir of atomic gas (HI) at large galactocentric radii is swept inward where it is converted into molecular gas (H2).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2016
- DOI:
- 10.3847/0004-637X/825/2/128
- arXiv:
- arXiv:1605.05417
- Bibcode:
- 2016ApJ...825..128L
- Keywords:
-
- galaxies: evolution;
- galaxies: interactions;
- infrared: galaxies;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- doi:10.3847/0004-637X/825/2/128