Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008apj...686..195z&link_type=abstract
The Astrophysical Journal, Volume 686, Issue 1, pp. 195-200.
Astronomy and Astrophysics
Astronomy
12
Cosmology: Dark Matter, Galaxies: Intergalactic Medium, Quasars: Individual (Sdss J1711+6052), Quasars: Individual (Sdss J2346-0016), Surveys, Ultraviolet: General
Scientific paper
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.
Anderson Scott F.
Chiu Kuenley
Hogan Craig J.
Kriss Gerard Anthony
Meiksin Avery
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