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Title

Galaxies at redshift ~0.5 around three closely spaced quasar sightlines

Author(s)

Crighton, Neil H. M.;  Morris, Simon L.;  Bechtold, Jill;  Crain, Robert A.;  Jannuzi, Buell T.;  Shone, Allen;  Theuns, Tom

Abstract

We examine the relationship between galaxies and the intergalactic medium at z > 1 using a group of three closely spaced background QSOs with z_em ~1 observed with the Hubble Space Telescope. Using a new grouping algorithm, we identify groups of galaxies and absorbers across the three QSO sightlines that may be physically linked. There is an excess number of such groups compared to the number we expect from a random distribution of absorbers at a confidence level of 99.9%. The same search is performed with mock spectra generated using a hydrodynamic simulation, and we find the vast majority of such groups arise in dense regions of the simulation. We find that at z > 0.5, groups in the simulation generally trace the large-scale filamentary structure as seen in the projected 2-d distribution of the HI column density in a ~30 h^-1 Mpc region. We discover a probable sub-damped Lyman-alpha system at z=0.557 showing strong, low-ionisation metal absorption lines. Previous analyses of absorption across the three sightlines attributed these metal lines to HI. We show that even when the new line identifications are taken into account, evidence remains for planar structures with scales of ~1 Mpc absorbing across the three sightlines. We identify a galaxy at z=0.2272 with associated metal absorption in two sightlines, each 200 kpc away. By constraining the star formation history of the galaxy, we show the gas causing this metal absorption may have been enriched and ejected by the galaxy during a burst of star formation 2 Gyr ago.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Monthly Notices of the Royal Astronomical Society, Vol. 402, no. 2 (Feb 2010), pp. 1273-1306

Publication year

2010

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Absorption;  Galaxy formation;  Hubble Space Telescope;  QSos

Publisher

Wiley-Blackwell

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2009.15963.x

Copyright

Copyright © 2009 The Authors. Journal compilation copyright © 2009 Royal Astronomical Society. The accepted manuscript of the paper is reproduced here in accordance with the copyright policy of the publisher. The definitive version is available at www.interscience.wiley.com.

Additional information

Simulations for this paper were carried out using the HPCx facility at the Edinburgh Parallel Computing Centre (EPCC) as part of the EC's DEISA 'Extreme Computing Initiative', and with the Cosmology Machine at the Institute for Computational Cosmology at Durham University. Many programs used for this analysis were written in Python using the Numpy and Scipy packages. Figures were produced using Matplotlib. The programs used are available from NC on request, or can be downloaded from an online code repository. Our analysis used observations made with the NASA/ESA Hubble Space Telescope, obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (STECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

Full text

Peer reviewed