Astron. Astrophys. 334, L45-L48 (1998)

Letter to the Editor

HST observations of the QSO pair Q1026-0045A,B ^*

Patrick Petitjean ^{1, 2}, Jean Surdej ^{3, 7}, Alain Smette ⁴, Peter Shaver ⁵, Jan Mücket ⁶ and Marc Remy <sup>3

1</sup> Institut d'Astrophysique de Paris - CNRS, 98bis Boulevard Arago, F-75014 Paris, France
² UA CNRS 173-DAEC, Observatoire de Paris-Meudon, F-92195 Meudon Principal Cedex, France
³ Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, B-4000 Liège, Belgium
⁴ NASA-Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA
⁵ European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany
⁶ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
⁷ Directeur de Recherches du FNRS, Belgium

Received 12 February 1998 / Accepted 23 April 1998

Abstract

The spatial distribution of the Ly forest is studied using new HST data for the quasar pair Q 1026-0045 A and B at  = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear separations between lines of sight of 300  kpc (  = 0.5) over the redshift range 0.833   z    1.438. From the observed numbers of coincident and anti-coincident Ly absorption lines, we conclude that, at this redshift, the Ly structures have typical dimensions of 500  kpc, larger than the mean separation of the two lines of sight. The velocity difference, , between coincident lines is surprisingly small (4 and 8 pairs with    50 and 200 km s^-1 respectively).

Metal line systems are present at  = 1.2651 and 1.2969 in A,  = 0.6320, 0.7090, 1.2651 and 1.4844 in B. In addition we tentatively identify a weak Mg II system at  = 0.11 in B. It is remarkable that the  = 1.2651 system is common to both lines of sight. The system at  = 1.4844 has strong O VI absorption.

There is a metal-poor associated system at  = 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. It is tempting to interpret this as the presence of a disk of radius larger than 300  kpc surrounding quasar A.

Key words: quasars: individual: Q 1026 0045A,B, galaxies: ISM, quasars:absorption lines, galaxies: halo

* Based on observations obtained with the NASA/ESA Hubble Space Telescope by the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555

Send offprint requests to: Patrick Petitjean (petitjean@iap.fr)

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998

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