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Astron. Astrophys. 343, 399-406 (1999)

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Did most high-redshift quasars escape detection?

C. Wolf 1, K. Meisenheimer 1, H.-J. Röser 1, S.V.W. Beckwith 1,3, R. Fockenbrock 1, H. Hippelein 1, B. von Kuhlmann 1, S. Phleps 1 and E. Thommes 2

1 Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
2 Royal Observatory, Blackfort Hill, Edinburgh EH9 3HJ, UK
3 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

Received 4 November 1998 / Accepted 15 December 1998


We present follow-up spectroscopy to the Calar Alto Deep Imaging Survey (CADIS), reporting on the quasars in the CADIS 16 h-field, and including preliminary data from two other fields. In this [FORMULA] field we found six quasars at redshift [FORMULA] which are brighter than [FORMULA], while surface densities determined in previous surveys are reported to be below one on average. This is the highest reported surface density of high-redshift quasars within the given limits. We believe this result to be a consequence of the multicolor database and the search technique used in CADIS.

Our observations further seem to indicate that the density of high-redshift quasars is also higher than predicted by the luminosity function of Warren et al. (1994) by a factor of three, implying that common search methods have overlooked the majority of high-redshift quasars at this magnitude level. In particular, an application of the [FORMULA] test to our preliminary list of AGNs with [FORMULA] and [FORMULA] yields [FORMULA], characterizing our preliminary redshift distribution as flat.

Key words: methods: data analysis – techniques: photometric – surveys – galaxies: quasars: general – cosmology: observations

SIMBAD Objects


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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999