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


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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 3

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

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

There is a metal-poor associated system at [FORMULA]  = 1.4420 along the line of sight to A with complex velocity profile. We detect a strong Ly [FORMULA] 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 [FORMULA]  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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