C-GOALS

II. Chandra observations of the lower luminosity sample of nearby luminous infrared galaxies in GOALS

¹ Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Martí i Franquès, 1, 08028 Barcelona, Spain
e-mail: ntorresalba@icc.ub.edu
² ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
³ Núcleo de Astronomía de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
⁴ Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing, National Observatory of Athens, 15236 Penteli, Greece
⁵ University of Crete, Department of Physics, 71003 Heraklion, Greece
⁶ Kavli Institute for Astronomy and Astrophysics, Peking University, 100871 Beijing, PR China
⁷ Chinese Academy of Sciences South America Center for Astronomy, Camino El Observatorio 1515, Las Condes, Santiago, Chile
⁸ Gemini North Observatory, 670 N. A’ohoku Place, Hilo, HI, 96720, USA
⁹ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA
¹⁰ Infrared Processing and Analysis Center, MC 314-6, Caltech, 1200 E. California Blvd., Pasadena, CA, 91125, USA
¹¹ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903, USA
¹² Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
¹³ Department of Astronomy, University of Virginia, PO Box 400325 Charlottesville, VA, 22904, USA
¹⁴ Univ Lyon, Univ Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon (CRAL) UMR5574, 69230 Saint Genis-Laval, France
¹⁵ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA, 91125, USA
¹⁶ Research School of Astronomy & Astrophysics, Australian National University, ACT 2611 Canberra, Australia
¹⁷ Department of Astronomy, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL, 32611, USA
¹⁸ Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA, 92697, USA

Received: 18 August 2018
Accepted: 2 October 2018

Abstract

We analyze Chandra X-ray observatory data for a sample of 63 luminous infrared galaxies (LIRGs), sampling the lower-infrared luminosity range of the Great Observatories All-Sky LIRG survey (GOALS), which includes the most luminous infrared selected galaxies in the local Universe. X-rays are detected for 84 individual galaxies within the 63 systems, for which arcsecond resolution X-ray images, fluxes, infrared and X-ray luminosities, spectra and radial profiles are presented. Using X-ray and mid-infrared (MIR) selection criteria, we find AGN in (31 ± 5)% of the galaxy sample, compared to the (38 ± 6)% previously found for GOALS galaxies with higher infrared luminosities (C-GOALS I). Using MIR data, we find that (59 ± 9)% of the X-ray selected AGN in the full C-GOALS sample do not contribute significantly to the bolometric luminosity of the host galaxy. Dual AGN are detected in two systems, implying a dual AGN fraction in systems that contain at least one AGN of (29 ± 14)%, compared to the (11 ± 10)% found for the C-GOALS I sample. Through analysis of radial profiles, we derive that most sources, and almost all AGN, in the sample are compact, with half of the soft X-ray emission generated within the inner ∼1 kpc. For most galaxies, the soft X-ray sizes of the sources are comparable to those of the MIR emission. We also find that the hard X-ray faintness previously reported for the bright C-GOALS I sources is also observed in the brightest LIRGs within the sample, with L_FIR > 8 × 10¹⁰ L_⊙.