Journal Article

The transverse proximity effect in the <i>z</i>∼ 2 Lyman α forest suggests quasi-stellar object episodic lifetimes of ∼1 Myr

David Kirkman and David Tytler

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 3, pages 1457-1471
Published in print December 2008 | ISSN: 0035-8711
Published online November 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13994.x
The transverse proximity effect in the z∼ 2 Lyman α forest suggests quasi-stellar object episodic lifetimes of ∼1 Myr

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We look for signs of the H i transverse proximity effect in the spectra of 130 quasi-stellar object (QSO) pairs, most with transverse separations in the plane of the sky of 0.1–3 Mpc at z∼ 2.2. We expected to see a decrease in Lyα forest H i absorption in the spectrum of background QSOs near the position of foreground QSOs. Instead, we see no change in the absorption in front of the foreground QSOs, and we see evidence for a 50 per cent increase in the absorption out to 6 Mpc behind the foreground QSOs. Further, we see no change in the H i absorption along the line-of-sight to the foreground QSOs, the normal line-of-sight proximity effect. We may account for the lack of change in the H i absorption if the effect of extra ultraviolet photons is cancelled by higher gas density around QSOs. If so, the increase in absorption behind the QSOs then suggests that the higher gas density there is not cancelled by the UV radiation from the QSOs. We can explain our observations if QSOs have had their current UV luminosities for less than approximately a million years, a time-scale that has been suggested for accretion disc instabilities and gas depletion.

Keywords: intergalactic medium; quasars: absorption lines; cosmology: observations

Journal Article.  14176 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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