Star-forming galactic contrails as a source of metal enrichment and ionizing radiation at high redshift

Creators: Rauch, Michael; Becker, George D.; Haehnelt, Martin G.; Gauthier, Jean-René

Abstract

A spectroscopically detected Lyman α emitting halo at redshift 3.216 in the GOODS-N field is found to reside at the convergence of several line-emitting filaments. Spatially extended emission apparently by He II 1640 Å and several metal transitions is seen within several arcseconds from the position of the central galaxy. The V = 24.9 galaxy mainly responsible for the continuum emission at the centre of the halo has broad-band colours and spectral features consistent with a z = 3.216 star-forming galaxy. Hubble Space Telescope images show that some of the filaments coincide, in projection, with several, mostly blue galaxies, with pronounced head–tail structures partly aligned with each other. These objects, for which we cannot rule that they are foreground, chance projections in front of the high-redshift halo, are seen over an area with a linear extent of at least 12 arcsec. The broad-band images of some galaxies suggest the presence of ram-pressure stripping, including possible evidence for recent star formation in the stripped contrails. Spatial gradients in the appearance of several galaxies may represent a stream of galaxies passing from a colder to a hotter intergalactic medium. The release of the enriched interstellar medium from galaxies and the occurrence of star formation and stellar feedback in the galactic contrails suggest a mechanism for the metal enrichment of the high-redshift intergalactic medium that does not require long-range galactic winds. If these galaxies are at the same redshift as the Lyα halo, their very blue colours may be a consequence of the stripping of gas. A stripped stellar population and star formation in galactic contrails suggest promising sites for the escape of ionizing radiation from high-redshift galaxies.

Additional Information

© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 March 13. Received 2014 March 13; in original form 2013 May 24. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The data were obtained as part of a long term collaboration with the late Wal Sargent, to whose memory we dedicate this paper. We thank the anonymous referee for useful and critical suggestions that led to clarifications and improvements of the paper. We acknowledge helpful discussions with Guillermo Blanc, Bob Carswell, Michele Fumagalli, and Andy McWilliam. We thank the staff of the Keck Observatory for their help with the observations. MR is grateful to the National Science Foundation for grant AST-1108815. GB has been supported by the Kavli Foundation, and MGH received support by the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement no. 320596. JRG acknowledges a Millikan Fellowship at Caltech. We acknowledge use of the Atomic Line List v2.05, maintained by Peter van Hoof and the use of the NIST Atomic Spectra Database (ver. 5.0; Kramida et al. 2012). This research has further made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and of the VizieR catalogue access tool.

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