Astron. Astrophys. 332, 814-824 (1998)

Ly absorbers at : HST-CFHT imaging and spectroscopy in the field of 3C 286 ^*

V. Le Brun ¹ and J. Bergeron <sup>2, 3

1</sup> Laboratoire d'Astronomie Spatiale du C.N.R.S., B.P. 8, F-13376 Marseille, France (lebrun@lasa13.astrsp-mrs.fr)
² European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. M"unchen, Germany (jbergero@eso.org)
³ Institut d'Astrophysique de Paris, CNRS, 98bis boulevard Arago, F-75014 Paris, France

Received 5 May 1997 / Accepted 19 January 1998

Abstract

We present further observational results on our -only absorber identification project at low and intermediate redshifts. We combine CFHT/MOS imaging and spectroscopic observations of 25 galaxies in the field of the quasar 3C 286 () with HST/FOS spectrum of the quasar between 1600 and 3000 Å and HST/WFPC2 high spatial resolution imaging of some galaxies.

Our results confirm our first conclusions on the nature of the intermediate redshift forest absorbers. A small fraction of them is tightly linked to galaxies, and most probably arise in the external parts of giant halos (  kpc) around fairly luminous galaxies () of various spectral and morphological types, as shown by HST imaging of these objects. Most of the absorbing clouds appear to be only "associated" with galaxies, in the sense that they could trace the gaseous filaments or sheets of large-scale structures. Thus, as expected from a sample tracing large scale structures, these galaxies have various spectral types.

We also find that groups of galaxies have always at least one associated absorption line.

Key words: quasar: absorption lines galaxies: ISM galaxies: halos

* Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, and with the Canada-France-Hawaii Telescope

Send offprint requests to: V. Le Brun

SIMBAD Objects

Contents

• 1. Introduction
• 2. Presentation of the data
  • 2.1. HST data
  • 2.2. Galaxy population of the field (MOS imaging)
  • 2.3. MOS spectroscopic data
• 3. Characteristics of the identified galaxies
  • 3.1. The lower redshift objects
    • 3.1.1. The group at
    • 3.1.2. The group at
    • 3.1.3. The group at
  • 3.2. The group at
  • 3.3. The group at
  • 3.4. The group at
  • 3.5. Isolated foreground galaxies
    • 3.5.1. The galaxies at and 0.4575
    • 3.5.2. The galaxies at and
    • 3.5.3. The galaxy at
  • 3.6. The galaxy at
• 4. Discussion on the forest absorbers
  • 4.1. Overall properties of the galaxy- absorber associations
  • 4.2. Association as a function of impact parameter
  • 4.3. Relation with groups or clusters of galaxies
• References

© European Southern Observatory (ESO) 1998

Online publication: March 30, 1998
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