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For refcode 1989AJ.....98..419V:
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1989AJ.....98..419V STRUCTURES, SPECTRAL INDEXES, AND OPTICAL IDENTIFICATIONS OF RADIO SOURCES SELECTED FROM THE B3 CATALOGUE M. VIGOTTI Istituto di Radioastronomia C.N.R., Via Irnerio 46, Bologna, Italy G. GRUEFF Dipartimento di Astronomia, University of Bologna, Via Zamboni 33, Bologna, Italy and Istituto di Radioastronomia C.N.R., Via Irnerio 46, Bologna, Italy R. PERLEY AND B. G. CLARK National Radio Astronomy Observatory, Socorro, New Mexico 87801 A. H. BRIDLE National Radio Astronomy Observatory, Charlottesville, Virginia 22903-2475 Received 27 September 1988; revised 13 January 1989 ABSTRACT This paper presents the first results of a large program of optical identifications of radio sources from Third Bologna (B3) Catalogue. A homogeneous sample of 1103 radio sources, selected from the B3 catalogue at 408 MHz and covering the flux-density range from 2.0 to 0.1 Jy, has been mapped at 1465 MHz using the VLA at 15 arcsec resolution. Both positonal and structural information have been derived and are presented here. Optical identifications have been attempted for all of the sources using Palomar Sky Survey prints, resulting in 354 proposed identifications. The run of identification percentage, largest angular size (LAS), and spectral index with flux density is analyzed. Evidence is given that sizable intrinsic radio- optical displacements are possible for steep-spectrum unresolved sources. The fraction of "empty field" identifications (fainter than m_r_=20) increases from 15% for S_408_ >= 10 Jy to 86% in the 20-60 mJy interval. The 408-1465 MHz spectra become steeper with decreasing flux density to about 50 mJy, and become flatter at lower flux densities. Correspondingly, a small discontinuity is found in the behavior of the apparent diameter versus flux-density relation, at a similar flux density. A negative correlation is found between the metric size and redshift for radio galaxies, confirming an earlier result of Grueff et al. (1977).
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