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Galaxy And Mass Assembly (GAMA): The 325 MHz Radio Luminosity Function of AGN and Star Forming Galaxies

Prescott, M and Mauch, T and Jarvis, MJ and McAlpine, K and Smith, DJB and Fine, S and Johnston, R and Hardcastle, MJ and Baldry, IK and Brough, S and Brown, MJI and Bremer, MN and Driver, SP and Hopkins, AM and Kelvin, LS and Loveday, J and Norberg, P and Obreschkow, D and Sadler, EM (2016) Galaxy And Mass Assembly (GAMA): The 325 MHz Radio Luminosity Function of AGN and Star Forming Galaxies. Monthly Notices of the Royal Astronomical Society, 457 (1). pp. 730-744. ISSN 0035-8711

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Abstract

Measurement of the evolution of both active galactic nuclei (AGN) and star-formation in galaxies underpins our understanding of galaxy evolution over cosmic time. Radio continuum observations can provide key information on these two processes, in particular via the mechanical feedback produced by radio jets in AGN, and via an unbiased dust-independent measurement of star-formation rates. In this paper we determine radio luminosity functions at 325 MHz for a sample of AGN and star-forming galaxies by matching a 138 deg sq. radio survey conducted with the Giant Metrewave Radio Telescope (GMRT), with optical imaging and redshifts from the Galaxy And Mass Assembly (GAMA) survey. We find that the radio luminosity function at 325 MHz for star-forming galaxies closely follows that measured at 1.4 GHz. By fitting the AGN radio luminosity function out to $z = 0.5$ as a double power law, and parametrizing the evolution as ${\Phi} \propto (1 + z)^{k}$ , we find evolution parameters of $k = 0.92 \pm 0.95$ assuming pure density evolution and $k = 2.13 \pm 1.96$ assuming pure luminosity evolution. We find that the Low Excitation Radio Galaxies are the dominant population in space density at lower luminosities. Comparing our 325 MHz observations with radio continuum imaging at 1.4 GHz, we determine separate radio luminosity functions for steep and flat-spectrum AGN, and show that the beamed population of flat-spectrum sources in our sample can be shifted in number density and luminosity to coincide with the unbeamed population of steep-spectrum sources, as is expected in the orientation based unification of AGN.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record "Galaxy And Mass Assembly (GAMA): The 325 MHz Radio Luminosity Function of AGN and Star Forming Galaxies" is available online at http://dx.doi.org/10.1093/mnras/stv3020
Uncontrolled Keywords: astro-ph.GA; astro-ph.GA
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 08 Jan 2016 10:53
Last Modified: 31 Mar 2016 09:31
DOI or Identification number: 10.1093/mnras/stv3020
URI: http://researchonline.ljmu.ac.uk/id/eprint/2540

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