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Counts of quasars at faint magnitudes: a new complete sample*

Published online by Cambridge University Press:  19 July 2016

G. Zamorani ,
V. Zitelli  and
B. Marano
G. Zamorani
Affiliation:
Istituto di Radioastronomia, Via Irnerio 46, 40126 Bologna, Italy
V. Zitelli
Affiliation:
Dipartimento di Astronomia, Via Zamboni 33, 40126 Bologna, Italy
B. Marano
Affiliation:
Dipartimento di Astronomia, Via Zamboni 33, 40126 Bologna, Italy

Abstract

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We present results on a new sample of optically selected quasar candidates. The “standard” multicolor technique for selecting quasar candidates has been applied to all the objects brighter than J = 22.0 in a field of 0.69 square degrees. Additional candidates have been selected from a search on grism plates obtained in the same area. Spectroscopy for all the candidates brighter than J = 20.9 has provided a sample of 22 confirmed quasars. The redshift distribution of these objects is essentially flat from z = 0.6 up to z = 2.8. Three out of the eight quasars with redshift larger than two were selected from the grism plates and were missed by our color selection. This result, although based on a small number of objects, suggests that the luminosity functions computed in this redshift range from samples which are only color selected might have to be increased by a factor up to 1.5. On the other hand, these possible losses of the multicolor search technique are negligible (of the order of 15% only) for the estimates of the integral number counts at magnitudes of the order 20–21.

Type
I. Surveys
Information
Symposium - International Astronomical Union , Volume 119: Quasars , 1986 , pp. 33 - 36
Copyright
Copyright © Reidel 1986 

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