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Title:
Intergalactic He II Absorption in the Spectra of Quasars at Redshifts 3.5 and 3.8, Observed with the HST ACS Prism
Authors:
Zheng, Wei; Meiksin, Avery; Pifko, Keith; Anderson, Scott F.; Hogan, Craig J.; Tittley, Eric; Kriss, Gerard A.; Chiu, Kuenley; Schneider, Donald P.; York, Donald G.; Weinberg, David H.
Affiliation:
AA(Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218.), AB(Scottish Universities Physics Alliance (SUPA); Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, United Kingdom.), AC(Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218.), AD(Department of Astronomy, University of Washington, Seattle, WA 98195.), AE(Department of Astronomy, University of Washington, Seattle, WA 98195.), AF(Scottish Universities Physics Alliance (SUPA); Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, United Kingdom.), AG(Space Telescope Science Institute, Baltimore, MD 21218.), AH(Anglo-Australian Observatory, Epping, NSW 1710, Australia.), AI(Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802.), AJ(Department of Astronomy and Astrophysics and the Enrico Fermi Institute, University of Chicago, Chicago, IL 60637.), AK(Department of Astronomy, Ohio State University, Columbus, OH 43210.)
Publication:
The Astrophysical Journal, Volume 686, Issue 1, pp. 195-200. (ApJ Homepage)
Publication Date:
10/2008
Origin:
UCP
ApJ Keywords:
Cosmology: Dark Matter, Galaxies: Intergalactic Medium, quasars: individual (SDSS J1711+6052), quasars: individual (SDSS J2346-0016), Surveys, Ultraviolet: General
DOI:
10.1086/590384
Bibliographic Code:
2008ApJ...686..195Z

Abstract

We present the UV spectra of two quasars obtained with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) prism (R~100). One quasar, at redshift z=3.5, shows an absorption edge consistent either with nearly fully ionized helium with an intergalactic He II Lyα optical depth at 304 Å of τ304>3.1 (90% confidence), or a He III region with edge 5.4 Mpc from the QSO. The spectrum of the second quasar, at z=3.8, has a broad absorption profile extending across the He II emission line of the quasar consistent with a damped absorption profile from an intervening He II system at z~=3.7 with a column density of approximately 1022 cm-2. In this case, the extremely high He II column density and absence of strong H I absorption suggests that the radiation field is quite weak at 4 ryd. The combined He II and H I signatures are consistent with photoionization by a compact (1-100 pc) star-forming region located approximately 10 Mpc from the quasar.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO 9759, 9806 and 10231.

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