UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

The central energy source of 70 μm-selected galaxies: starburst or AGN?

Symeonidis, M; Rosario, D; Georgakakis, A; Harker, J; Laird, ES; Page, MJ; Willmer, CNA; (2010) The central energy source of 70 μm-selected galaxies: starburst or AGN? Monthly Notices of the Royal Astronomical Society , 403 (3) 1474 - 1490. 10.1111/j.1365-2966.2009.16214.x. Green open access

[thumbnail of Page_The central energy source.pdf]
Preview
Text
Page_The central energy source.pdf - Published version

Download (1MB) | Preview

Abstract

We present the first active galactic nuclei (AGN) census in a sample of 61 galaxies selected at 70 μm, a wavelength which should strongly favour the detection of star-forming systems. For the purpose of this study, we take advantage of deep Chandra X-ray and Spitzer infrared (3.6–160 μm) data, as well as optical spectroscopy and photometry from the Deep Extragalactic Evolutionary Probe 2 (DEEP 2) survey for the Extended Groth Strip (EGS) field, as part of the All-Wavelength Extended Groth Strip International Survey. We investigate spectral line diagnostics ([O III]/Hβ and [Ne III]/[O II] ratios, Hδ Balmer absorption line equivalent widths and the strength of the 4000 Å break), X-ray luminosities and spectral energy distributions (SEDs). We find that the 70-μm sources are undergoing starburst (SB) episodes and are therefore characterized by a predominance of young stars. In addition, 13 per cent of the sources show AGN signatures and hence potentially host an AGN. When the sample is split into SBs (10^10 < L_IR < 10^11 L_sun), luminous infrared Galaxies (LIRGs; 10^11 < L_IR < 10^12 L_sun) and ultraluminous infrared Galaxies (ULIRGs; 10^12 < L_IR < 10^13 L_sun), the AGN fraction becomes 0, 11 and 23 per cent, respectively, showing an increase with total infrared luminosity. However, by examining the sources' panchromatic SEDs, we conclude that although the AGN is energetically important in 1 out of 61 objects all 70-μm-selected galaxies are primarily powered by star formation. When compared to a sample of DEEP 2 galaxies in the same redshift range and with similar optical colours, we find that the 70-μm population is characterized by younger stellar ages and a higher AGN incidence, indicating that strongly star-forming populations might be a key in studying the relationship between black hole and stellar growth.

Type: Article
Title: The central energy source of 70 μm-selected galaxies: starburst or AGN?
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/j.1365-2966.2009.16214.x
Publisher version: https://doi.org/10.1111/j.1365-2966.2009.16214.x
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: galaxies: active, galaxies: general, galaxies: high-redshift, galaxies: starburst, infrared: galaxies, X-rays: galaxies
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/136066
Downloads since deposit
47Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item