Selection of AGN candidates in the GOODS-South Field through Spitzer/MIPS 24 μm variability



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García González, Judit and Alonso Herrero, Almudena and Pérez González, Pablo Guillermo and Hernán Caballero, Antonio and Sarajedini, Vicki L. and Villar, Victor (2015) Selection of AGN candidates in the GOODS-South Field through Spitzer/MIPS 24 μm variability. Monthly notices of the Royal Astronomical Society, 446 (3). pp. 3199-3223. ISSN 0035-8711

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We present a study of galaxies showing mid-infrared variability in data taken in the deepest Spitzer/MIPS 24 mu m surveys in the Great Observatory Origins Deep Survey South field. We divide the data set in epochs and subepochs to study the long-term (months-years) and the short-term (days) variability. We use a chi^(2)-statistics method to select active galactic nucleus (AGN) candidates with a probability <≤ 1% that the observed variability is due to statistical errors alone. We find 39 (1.7 per cent of the parent sample) sources that show long-term variability and 55 (2.2 per cent of the parent sample) showing short-term variability. That is, 0.03 sources x arcmin^(-2) for both, long-term and short-term variable sources. After removing the expected number of false positives inherent to the method, the estimated percentages are 1.0 and 1.4 per cent of the parent sample for the long term and short term, respectively. We compare our candidates with AGN selected in the X-ray and radio bands, and AGN candidates selected by their IR emission. Approximately, 50 per cent of the MIPS (Multiband Imaging Photometer for Spitzer) 24 mu m variable sources would be identified as AGN with these other methods. Therefore, MIPS 24 μm variability is a new method to identify AGN candidates, possibly dust obscured and low-luminosity AGN, that might be missed by other methods. However, the contribution of the MIPS 24 mu m variable identified AGN to the general AGN population is small (≤ 13%) in GOODS-South.

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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 Selection of AGN candidates in the GOODS-South Field through Spitzer/MIPS 24 μm variability is available online at: JG-G, AA-H, and AH-C acknowledge support from the Augusto G. Linares research programme of the Universidad de Cantabria and from the Spanish Plan Nacional through grant AYA2012-31447.PGP-G acknowledges support from MINECO grant AYA2012-31277.This work has made use of the Rainbow Cosmological Surveys Database, which is operated by the Universidad Complutense de Madrid (UCM), partnered with the University of California Observatories at Santa Cruz (UCO/Lick,UCSC). This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Uncontrolled Keywords:Active galactic nuclei; Star-forming galaxies; Supermassive black-holes; Point-source catalogs; Hubble deep field; X-ray sources; Midinfrared selection; Photometric redshifts; Spectral properties; Formation history
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
ID Code:29649
Deposited On:21 Apr 2015 11:22
Last Modified:10 Dec 2018 15:05

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