A1 Journal article – refereed

GAMA/XXL: X-ray point sources in low-luminosity galaxies in the GAMA G02/XXL-N field




List of Authors: Nwaokoro E, Phillipps S, Young AJ, Baldry I, Bongiorno A, Bremer MN, Brown MJI, Chiappetti L, De Propris R, Driver SP, Elyiv A, Fotopoulou S, Giles PA, Hopkins AM, Maughan B, McGee S, Pacaud F, Pierre M, Plionis M, Poggianti BM, Vignali C, Vignali C

Publisher: OXFORD UNIV PRESS

Publication year: 2021

Journal: Monthly Notices of the Royal Astronomical Society

Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Journal acronym: MON NOT R ASTRON SOC

Volume number: 502

Issue number: 2

Number of pages: 12

ISSN: 0035-8711

DOI: http://dx.doi.org/10.1093/mnras/stab242


Abstract
Relatively few X-ray sources are known that have low-mass galaxies as hosts. This is an important restriction on studies of active galactic nuclei (AGNs), hence black holes, and of X-ray binaries (XRBs) in low-mass galaxies; addressing it requires very large samples of both galaxies and X-ray sources. Here, we have matched the X-ray point sources found in the XXL-N field of the XXL survey (with an X-ray flux limit of similar to 6 x 10(-15) erg s(-1)cm(-2) in the [0.5-2] keV band) to galaxies with redshifts from the Galaxy And Mass Assembly (GAMA) G02 survey field (down to a magnitude limit r = 19.8) in order to search for AGNs and XRBs in GAMA galaxies, particularly those of low optical luminosity or stellar mass (fainter than M-r = -19 or M-* less than or similar to 10(9.5) M-circle dot). Out of a total of 1200 low-mass galaxies in the overlap region, we find a total of 28 potential X-ray source hosts, though this includes possible background contaminants. From a combination of photometry (optical and infrared colours), positional information, and optical spectra, we deduce that most of the similar or equal to 20 X-ray sources genuinely in low-mass galaxies are high-mass X-ray binaries in star-forming galaxies. None of the matched sources in a low-mass galaxy has a BPT classification as an AGN, and even ignoring this requirement, none passes both criteria of close match between the X-ray source position and optical galaxy centre (separation <= 3 arcsec) and high [OIII] line luminosity (above 10(40.3)ergs(-1)).

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Last updated on 2021-06-08 at 14:43