Bielby, R. M. and Stott, J. P. and Cullen, F. and Tripp, T. M. and Burchett, J. N. and Fumagalli, M. and Morris, S. L. and Tejos, N. and Crain, R. A. and Bower, R. G. and Prochaska, J. X. (2019) Quasar Sightline and Galaxy Evolution (QSAGE) survey - I. The galaxy environment of O VI absorbers up to z = 1.4 around PKS 0232-04. Monthly Notices of the Royal Astronomical Society, 486 (1). pp. 21-41. ISSN 0035-8711
1809.05544.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial.
Download (2MB)
Abstract
We present the first results from a study of O VI absorption around galaxies at z <1.44 using data from a near-infrared grism spectroscopic Hubble Space Telescope Large Programme, the Quasar Sightline and Galaxy Evolution (QSAGE) survey. QSAGE is the first grism galaxy survey to focus on the circumgalactic medium at z similar to 1, providing a blind survey of the galaxy population. The galaxy sample is H alpha flux limited (f(H alpha) > 2 x 10(-17) erg s(-1) cm(-2)) at 0.68 <z <1.44, corresponding to greater than or similar to 0.2-0.8 M-circle dot yr(-1). In this first of 12 fields, we combine the galaxy data with high-resolution STIS and COS spectroscopy of the background quasar to study O VI in the circumgalactic medium. At z similar to 1, we find O VI absorption systems up to b similar to 350 kpc (similar to 4R(vir)) from the nearest detected galaxy. Further, we find similar to 50 per cent of greater than or similar to 1 M-circle dot yr(-1) star-forming galaxies within 2R(vir) show no associated O VI absorption to a limit of at least N(O VI) = 10(13.9) cm(-2). That we detect O VI at such large distances from galaxies and that a significant fraction of star-forming galaxies show no detectable O VI absorption disfavours outflows from ongoing star formation as the primary medium traced by these absorbers. Instead, by combining our own low-and high-redshift data with existing samples, we find tentative evidence for many strong (N(O VI) > 10(14) cm(-2)) O VI absorption systems to be associated with M-star similar to 10(9.5-10) M-circle dot mass galaxies (M-halo similar to 10(11.5-12) M-circle dot dark matter haloes), and infer that they may be tracing predominantly collisionally ionized gas within the haloes of such galaxies.