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HST spectroscopy of the double QSO HS 1216+5032 AB *
H.-J. Hagen and
Received 6 August 1999 / Accepted 27 March 2000
We report on Hubble Space Telescope Faint Object Spectrograph observations of the double QSO HS 1216+5032 AB (; , and angular separation ). The spectral coverage is 910 Å to 1340 Å in the QSO rest-frame. An unusual broad-absorption-line (BAL) system is observed only in the B component: maximum outflow velocity of km s-1; probably a mixture of broad and narrow components. Observed ions are: HI , CII , CIII , NIII , NV , OVI , and possibly SIV and SVI . We also discuss two outstanding intervening systems: (1) a complex CIV system at of similar strength in A and B, with a velocity span of 1500 km s-1 along the lines of sight (LOSs; LOS separation: kpc); and (2) a possible strong MgII system at observed in B only, presumably arising in a damped Ly system.
We assume HS 1216+5032 is a binary QSO but discuss the possibility of a gravitational lens system. The size of Ly forest clouds is constrained using kpc at redshifts between and 1.45. Four Ly systems not associated with metal lines and producing lines with Å are observed in both spectra, while five appear in only one spectrum. This sample, although scarce due to the redshift path blocked out by the BALs in B, allows us to place upper limits on the transverse cloud sizes. Modelling the absorbers as non-evolving spheres, a maximum-likelihood analysis yields a most probable cloud diameter kpc and bounds of kpc. If the clouds are modelled as filamentary structures, the same analysis yields lower transverse dimensions by a factor of two. Independently of the maximum-likelihood approach, the equivalent width differences provide evidence for coherent structures. The suggestion that the size of Ly forest clouds increases with decreasing redshift is not confirmed. Finally, we discuss two Ly systems observed in both QSO spectra.
Key words: galaxies: quasars: absorption lines galaxies: quasars: general cosmology: observations galaxies: quasars: individual: HS 1216+5032
Present address: Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
Send offprint requests to: S. Lopez (email@example.com)
Online publication: May 3, 2000