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

  • E. Nwaokoro (Creator)
  • S Phillipps (Creator)
  • Alyssa J. Young (Creator)
  • I. K. Baldry (Creator)
  • A. Bongiorno (Creator)
  • Malcolm N. Bremer (Creator)
  • Jeffrey M. Brown (Creator)
  • L. Chiappetti (Creator)
  • Roberto De Propris (Creator)
  • Simon Driver (Creator)
  • A. Elyiv (Creator)
  • S. Fotopoulou (Creator)
  • Paul A. Giles (Creator)
  • Andrew M. Hopkins (Creator)
  • B. Maughan (Creator)
  • Sean Mcgee (Creator)
  • F. Pacaud (Creator)
  • Marguerite Pierre (Creator)
  • M. Plionis (Creator)
  • B.M. Poggianti (Creator)



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 ~6 × 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 Mr = -19 or M∗≲109.5M⊙ ). 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 ≃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 [O III] line luminosity (above 1040.3 erg s-1).
Date made availableApr 2021
PublisherSAO/NASA Astrophysics Data System (ADS)


  • galaxies: active
  • galaxies: star formation
  • X-rays: galaxies

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