A survey of ultraviolet-bright sources behind the halo of M31 |
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| Authors: | Andrew Fittingoff J Xavier Prochaska Jasonjot S Kalirai Jay Strader † Puragra Guhathakurta Kyle F Kaplan |
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| Institution: | Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA;University of California Observatories –Lick Observatory, University of California, Santa Cruz, CA 95064, USA;Space Telescope Science Institute, Baltimore, MD 21218, USA;Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA |
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| Abstract: | We have performed a wide-area ultraviolet (UV) imaging survey using the GALaxy Evolution eXplorer to search for bright, point-like UV sources behind M31's extended halo. Our survey consisted of 46 pointings covering an effective area of ≈50 deg2, in both the far-UV and near-UV channels. We combined these data with optical R -band observations acquired with the WIYN Mosaic-1 imager on the Kitt Peak National Observatory 0.9-m WIYN telescope. An analysis of the brightness and colours of sources matched between our photometric catalogues yielded ≈100 UV-bright quasar candidates. We have obtained discovery spectra for 76 of these targets with the Kast spectrometer on the Lick 3-m telescope and confirmed 30 active galactic nuclei and quasars, 29 galaxies at z > 0.02 including several early-type systems, 16 Galactic stars (hot main-sequence stars) and one featureless source previously identified as a BL Lac object. Future UV spectroscopy of the brightest targets with the Cosmic Origins Spectrograph on the Hubble Space Telescope will enable a systematic search for diffuse gas in the extended halo of M31. |
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| Keywords: | galaxies: haloes galaxies: individual: M31 quasars: absorption lines |
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