FUSE Observations of the He II Ly alpha Forest and Implications for the Ionizing Radiation Field

Details FUSE Observations of the He II Ly alpha Forest and Implications for the Ionizing Radiation Field FUSE Observations of the He II Ly alpha Forest and Implications for the Ionizing Radiation Field

Jun 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003rmxac..17..297k&link_type=abstract

Galaxy Evolution: Theory & Observations (Eds. Vladimir Avila-Reese, Claudio Firmani, Carlos S. Frenk & Christine Allen) Revista

Astronomy and Astrophysics

Astronomy

Cosmology: Diffuse Radiation, Cosmology: Observations, Galaxies: Intergalactic Medium, Galaxies: Quasars: Individual (He2347-4342), Ultraviolet: General

Scientific paper

We present Far-Ultraviolet Spectroscopic Explorer observations of the line of sight to the quasar HE2347-4342 in the 1000-1187 Å band at a resolving power of 15,000. We resolve the He II Ly alpha absorption as a discrete forest of absorption lines in the redshift range 2.3 to 2.7. About 50 percent of these features have H I counterparts in Keck spectra. The He II to H I column density ratio ranges from 1 to > 1000 with an average of 80. Its distribution is comparable to the distribution of spectral indices of radio-quiet quasars. Ratios of < 100 are consistent with photoionization of the absorbing gas by a hard ionizing spectrum resulting from the integrated light of quasars. However, many absorption features show ratios of > 100 that indicate additional contributions to the ionizing radiation field from starburst galaxies or heavily filtered quasar radiation. Fluctuations in the ratio on the scale of individual features implie that the ionizing radiation field is not uniform.

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