P20	March 1998

Spatial distribution of the Ly- forest

¹ Institut d'Astrophysique de Paris - CNRS, 98bis Bd Arago, F-75014, Paris, France
² Institut d'Astrophysique et de Géophysique - Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium
³ NASA-Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA
⁴ Astrophysikalisches Institut Postdam, An der Sternwarte 16, D-14482 Postdam, Germany
⁵European Southern Observatory, Schwarzschild Strasse 2, D-80547 Garching, Germany

^* Directeur de Recherches FNRS, Belgium

Abstract

     The spatial distribution of the Ly forest is studied using new HST data of the quasar pair Q1026-0045 A and B at z_em = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear separations between lines of sight of ~300 h₅₀^-1 kpc (q₀ = 0) over the redshift range 0.833 < z < 1.438. From the observed number of coincident and anti-coincident Ly absorption lines, we conclude that, at this redshift, the Ly structures have typical dimensions of ~500 h₅₀^-1 kpc, larger than the mean separation of the two lines of sight. The velocity difference, V, between coincident lines is surprinsingly small (4 and 8 pairs with V < 50 and 200 km s^-1 respectively).

     There is a metal poor associated system at z_abs = 1.4420 along the line of sight to A with complex velocity profile. We detect a strong Ly absorption along the line of sight to B redshifted by only 300 km s^-1 relatively to the associated system. Given the strong proximity effect from quasar A, it is tempting to interpret this as the presence of a disk of radius larger than ~300 h₅₀^-1 kpc surrounding quasar A.