Molecular gas and dust properties of galaxies from the Great Observatories All-sky LIRG Survey^⋆

¹ European Southern Observatory (ESO), Alonso de Córdova 3107, Casilla, 19001 Vitacura, Santiago de Chile, Chile
e-mail: rherrero@eso.org
² Instituto de Astrofísica de Andalucía – CSIC, PO Box 3004 18008 Granada, Spain
³ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
⁴ Department of Astronomy, University of Florida, PO Box 112055 Gainesville, FL 32611, USA
⁵ Department of Astronomy, University of Virginia, Charlottesville, VA 22903, USA
⁶ National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
⁷ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
⁸ Visiting Scientist: Facultad de Ciencias, Univ. de Zaragoza, Zaragoza, Spain
⁹ Department of Physics and Astronomy, University of California, 4129 Frederick Reines Hall, Irvine, CA 92697, USA
¹⁰ ICREA and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
¹¹ Spitzer Science Center, California Institute of Technology, Pasadena, CA 91106, USA
¹² Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
¹³ Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
¹⁴ Gemini North Observatory, 670 N. A‘ohoku Place, Hilo, HI 96720, USA
¹⁵ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr, Honolulu, HI 96822, USA
¹⁶ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
¹⁷ Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing, National Observatory of Athens, 15236 Penteli, Greece
¹⁸ Green Bank Observatory, Green Bank, WV 24944, USA
¹⁹ National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA

Received: 14 August 2018
Accepted: 29 June 2019

Abstract

We present IRAM-30 m Telescope ¹²CO and ¹³CO observations of a sample of 55 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe. This sample is a subset of the Great Observatory All-Sky LIRG Survey (GOALS), for which we use ancillary multi-wavelength data to better understand their interstellar medium and star formation properties. Fifty-three (96%) of the galaxies are detected in ¹²CO, and 29 (52%) are also detected in ¹³CO above a 3σ level. The median full width at zero intensity (FWZI) velocity of the CO line emission is 661 km s⁻¹, and ∼54% of the galaxies show a multi-peak CO profile. Herschel photometric data is used to construct the far-IR spectral energy distribution of each galaxy, which are fit with a modified blackbody model that allows us to derive dust temperatures and masses, and infrared luminosities. We make the assumption that the gas-to-dust mass ratio of (U)LIRGs is comparable to local spiral galaxies with a similar stellar mass (i.e., gas/dust of mergers is comparable to their progenitors) to derive a CO-to-H₂ conversion factor of ⟨α⟩ = 1.8_−0.8^+1.3 M_⊙ (K km s⁻¹ pc²)⁻¹; such a value is comparable to that derived for (U)LIRGs based on dynamical mass arguments. We derive gas depletion times of 400 − 600 Myr for the (U)LIRGs, compared to the 1.3 Gyr for local spiral galaxies. Finally, we re-examine the relationship between the ¹²CO/¹³CO ratio and dust temperature, confirming a transition to elevated ratios in warmer systems.