ar X iv : a st ro - p h / 00 09 17 2 v 1 1 2 Se p 20 00 Where are the absorbers towards Q 2302 + 029 ?
نویسندگان
چکیده
We present images and spectroscopy of objects close to the sightline of Q2302+029 in order to search for galaxies responsible for the remarkable z = 0.7 high-ionization absorption line system found by Jannuzi et al. (1996). This system shows ‘normal’ narrow O VI, N V, and C IV lines superimposed on broader (3,000−5,000 km s−1 wide), unsaturated absorption troughs some 56,000 km s−1 away from the QSO emission redshift (zem = 1.052). Despite reaching sensitivities sufficient to detect 1/10L galaxies in the optical and 1/20L in the infra-red, we are unable to detect any obvious bright galaxies which might be responsible for the absorption beyond ≈ 6 h−1 kpc of the sightline. This supports the hypotheses that the absorption is either intrinsic to the QSO, or arises in intracluster gas. Adopting either explanation is problematic: in the first case, ‘associated’ absorption at such high ejection velocities is hard to understand, and challenges the conventional discrimination between intrinsic and intervening absorbers; in the second case, the gas must reside in a ∼ 40 h−1 Mpc long filament aligned along the line of sight in order to reproduce the broad absorption. Since the absorption system is unusual, such a chance alignment might not be unreasonable. Spectroscopy of objects beyond the immediate vicinity of the QSO sightline reveals a galaxy cluster at z = 0.59, which coincides with strong Lyα and more narrow high ionization lines in the quasar spectrum. Here too, the lack of galaxies at distances comparable to those found for, e.g., Lyα-absorbing galaxies, suggests that the absorption may arise from intracluster gas unassociated with any individual galaxies. Subject headings: quasars:absorption lines—quasars:individual (Q2302+029)—large-scale structure of universe
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