Identification of active galaxies behind the Coma cluster of galaxies

Astronomy & Astrophysics, Supplement Series 138, 109-117 (1999)

C. Ledoux [1], D. Valls-Gabaud [1,2], H. Reboul [3], P. Petitjean [5,6] and O. Moreau [7,8]

  1. UMR 7550 CNRS, Observatoire Astronomique de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg, France
  2. Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
  3. GRAAL, Université Montpellier II, F34095 Montpellier Cedex 5, France
  4. Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany
  5. Institut d'Astrophysique de Paris - CNRS, 98bis Boulevard Arago, F-75014 Paris, France
  6. DAEC, Observatoire de Paris-Meudon, F-92195 Meudon Principal Cedex, France
  7. Laboratoire d'Astronomie de l'Université Lille I, Impasse de l'Observatoire, F-59000 Lille, France
  8. Centre d'Analyse des Images, Observatoire de Paris, 61 avenue de l'Observatoire, F-75014 Paris, France


We describe the results of an efficient survey to identify bright B<~18 active galactic nuclei (AGN) within =~4 (4,7 h-1 Mpc projected radius) of the centre of the Coma cluster of galaxies. The candidates have been carefully selected either as unresolved UV-excess objects with no detected proper motion, or from identifications on objective-prism plates including a few ROSAT sources. A global success rate larger than 30% is achieved. Low-resolution spectra are presented for the extragalactic objects identified in the course of the survey: the sample contains 16 emission-line objects, a BL Lac candidate and an elliptical galaxy. The AGNs of this list are unique targets to study the association of the Lyman-alpha forest with large-scale structures and galactic haloes at low redshift, to search for warm gas within the Coma cluster and nearby filaments, and for optical monitoring to detect the microlensing variability produced by the baryonic dark matter in the cluster.

Key words: quasars: general -- quasars: absorption lines -- galaxies: Seyfert -- galaxies: starburst -- techniques: spectroscopic -- surveys

Contact: Dieter Engels.