EDP Sciences
Free access
Issue
A&A
Volume 369, Number 2, April II 2001
Page(s) 380 - 420
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010051


A&A 369, 380-420 (2001)
DOI: 10.1051/0004-6361:20010051

Multi-frequency VLA observations of a new sample of CSS/GPS radio sources

C. Fanti1, 2, F. Pozzi1, 3, D. Dallacasa2, 3, R. Fanti1, 2, L. Gregorini1, 2, C. Stanghellini4 and M. Vigotti2

1  Dipartimento di Fisica, Università di Bologna, Via Irnerio 46, 40126 Bologna, Italy
2  Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, 40127 Bologna, Italy
3  Istituto di Radioastronomia del CNR, Via Gobetti 101, 40129 Bologna, Italy
4  Istituto di Radioastronomia del CNR, CP 141, 96017 Noto SR, Italy

(Received 12 October 2000 / Accepted 3 January 2001 )

Abstract
In this paper we present a new sample of 87 Compact Steep Spectrum radio sources (CSS) with flux density $\geq$0.8 Jy at 0.4 GHz. This sample has been selected from the B3-VLA sample with the aid of new VLA observations at 4.9 and 8.5 GHz which allowed to clean an earlier selection based on VLA 1.5 GHz data. Redshifts, either spectroscopic or photometric, are known for 62% of the sources. About 75% of the sources are resolved or slightly resolved in the new observations. The range of measured linear sizes is from 20 h-1 kpc (selection upper limit) down to $\approx$0.5 h-1 kpc, which corresponds to our resolution limit. The Largest Linear Size (LLS) distribution is well represented by the power law ${\rm d}N/{\rm d}(LLS)\propto LLS^{-0.6}$, consistent with earlier results. The majority of the radio sources smaller than 0.5 h-1 kpc shows a marked spectral flattening at low frequencies. The four frequency spectra computed in the range 0.4-8.5 GHz display a significant steepening at high frequencies in the largest majority of cases. A considerable fraction of source components are polarized, with median values of their fractional polarization $\approx$6% and $\approx$4% at 8.5 and 4.9 GHz respectively.


Key words: catalogs -- galaxies: active -- radio continuum: galaxies -- quasar: general -- polarization -- radio spectra

Offprint request: D. Dallacasa, ddallaca@ira.bo.cnr.it

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