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Astron. Astrophys. 323, 47-55 (1997)

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The final optical identification content of the Einstein deep x-ray field in Pavo

I. John Danziger 1, 2 and Roberto Gilmozzi 2

1 Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34131 Trieste, Italy
2 European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching, Germany

Received 13 October 1995 / Accepted 13 December 1996


The optical identification of all sources revealed in the final analysis of the Einstein deep field observations in Pavo has been completed to the viable limits accessible to spectroscopy. This work combined with previously published data results in the identification of 16 AGN's with the real possibility of 3 further such identifications, while a further 2 probably are spurious. Another AGN is identified in an IPC exposure just outside the boundary of the four HRI exposures. One elliptical galaxy (or cluster) and one dMe star complete the tally. In a log N - log S plot the point represented by these 16-19 AGN's falls precisely on the extension of the line defined by the EMSS data, and somewhat below the line defined by the more recent deep field ROSAT data. It extends to fainter sensitivities than the previously published work from the Einstein observations of the same field. It is consistent with the more recently published data for Pavo obtained with ROSAT even though this latter reaches a slightly fainter sensitivity. This identification work therefore sets a firm lower limit to the AGN content of the X-ray identifications in Pavo.

By virtue of having selected in this survey intrinsically fainter-than-average AGN's it has been possible to show, by combination with data for higher luminosity quasars, that a correlation exists between the luminosities and (B-V) colours extending over a luminosity range of 6 magnitudes. This sequence coincides with the sequence obtained by plotting data for all AGN's in the same redshift range taken from the Véron and Véron catalogue. It is argued that the magnitude of this effect cannot be explained by the translation of various strong emission lines through the band-passes of the relevant filters. It may be explained by the influence of host galaxies.

Key words: galaxies: active – quasars: general – galaxies: Seyfert – X-rays: galaxies

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998