Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 1, 1981 | public
Journal Article Open

Investigation of the optical fields of flat-spectrum radio sources to faint limiting magnitudes


A deep optical survey of the fields of 16 flat-spectrum radio sources has been carried out using the Hale 5-m telescope, with a prototype charge-coupled device as a detector. These sources are members of a complete sample, selected as having S(2.7 GHz) > 1.5 Jy, and were either unidentified, or were identified with very faint objects on the prints of the Palomar Sky Survey. Identifications are found for 12 of these objects; six are galaxies and six are stellar objects. Identifications for the 2.7-GHz sample are therefore now 96 per cent complete, allowing much improved redshift distributions to be derived. Values of V/V_(max) for the sample members have also been calculated, with the result that 〈V/V_(max)〉 for the flat-spectrum quasars is 0.68, rather than the values nearer 0.5 derived from studies of deeper samples. This result indicates that both the steep-spectrum and flat-spectrum quasars undergo similar degrees of cosmological evolution.

Additional Information

© 1981 Royal Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1980 July 1. First published online September 1, 1981. We thank M. A. Carr, R. Lucinio, V. E. Nanow and J. D. Smith for indispensable aid in the construction of the instrument; the Director of the Institute of Astronomy, Cambridge, for the use of their x-y measuring machine; D. M. Odell, D. J. Titterington and P. J. Warner for help with the data reduction; and W. 0. Saxton for the use of the Photowrite machine. We thank the Director of the Hale Observatories for observing privileges on the 5-m telescope, and we are very grateful to members of the Wide Field Camera Team of the Space Telescope Project for permission to use their CCD detector for these observations. JAP and MACP thank the SRC for financial support.


Files (8.1 MB)
Name Size Download all
8.1 MB Preview Download

Additional details

August 19, 2023
October 19, 2023