Role of AGNs in the Luminous Infrared Galaxy phase since z ~ 3

Abstract

In order to understand the interactions between active galactic nuclei (AGN) and star formation during the evolution of galaxies, we investigate 142 galaxies detected in both X-ray and 70μm observations in the COSMOS (Cosmic Evolution Survey) field. All of our data are obtained from the archive, X-ray point source catalogs from Chandra and XMM-Newton observations; far-infrared 70μm point source catalog from Spitzer-MIPS observations. Although the IRAC [3.6μm]-[4.5μm] vs. [5.8μm]-[8.0μm] colours of our sample indicate that only ~63% of our sources would be classified as AGN, the ratio of the rest-frame 2-10 keV luminosity to the total infrared luminosity (8-1000μm) shows that all of the sample has comparatively higher X-ray luminosity than that expected from pure star-forming galaxies, suggesting the presence of an AGN in all of our sources. From the analysis of the X-ray hardness ratio, we find that sources with both 70μm and X-ray detection tend to have a higher hardness ratio relative to the whole X-ray selected source population, suggesting the presence of more X-ray absorption in the 70μm detected sources. In addition, we find that the observed far-infrared colours of 70μm detected sources with and without X-ray emission are similar, suggesting the far-infrared emission could be mainly powered by star formation.

15 pages, 10 figures and 3 Tables

References in corpus (25)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity
• COSMOS Photometric Redshifts with 30-bands for 2-deg2
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• The Chandra COSMOS Survey, I: Overview and Point Source Catalog
• Far-infrared Spectral Energy Distribution Fitting for Galaxies Near and Far
• Photometric redshift and classification for the XMM-COSMOS sources
• The XMM-Newton wide-field survey in the COSMOS field: I. Survey description
• SHARC-2 350 Micron Observations of Distant Submillimeter Selected Galaxies
• The incidence of obscuration in active galactic nuclei
• Spitzer Quasar and ULIRG Evolution Study (QUEST): II. The Spectral Energy Distributions of Palomar-Green Quasars
• The XMM-Newton wide-field survey in the COSMOS field. The point-like X-ray source catalogue
• AzTEC Millimetre Survey of the COSMOS Field: I. Data Reduction and Source Catalogue
• Spitzer's Contribution to the AGN Population
• HST WFC3/IR Observations of Active Galactic Nucleus Host Galaxies at z~2: Supermassive Black Holes Grow in Disk Galaxies
• The XMM-Newton wide-field survey in the COSMOS field: III. optical identification and multiwavelength properties of a large sample of X-ray selected sources
• Evidence for Merger Remnants in Early-Type Host Galaxies of Low-Redshift QSOs
• The Obscured Fraction of AGN in the XMM-COSMOS Survey: A Spectral Energy Distribution Perspective
• Magellan Spectroscopy of AGN Candidates in the COSMOS Field
• High-resolution radio observations of submillimetre galaxies
• XMM-Newton observations of the Lockman Hole V: time variability of the brightest AGN
• Quasars in the COSMOS Field
• Exploring the Connection Between Star Formation and AGN Activity in the Local Universe

Cited by in corpus (3)

• [Ultra] Luminous Infrared Galaxies selected at 90 $\mu$m in the AKARI deep field: a study of AGN types contributing to their infrared emission
• The OTELO survey. III. Demography, morphology, IR luminosity and environment of AGN hosts
• Nature of hard X-ray (3-24 keV) detected luminous infrared galaxies in the COSMOS field