Optical spectroscopy and polarization of a new sample of optically bright flat radio spectrum sources

M. J.M. Marchã, I. W.A. Browne, C. D. Impey, P. S. Smith

Research output: Contribution to journalArticle

194 Scopus citations

Abstract

A new sample of bright flat radio spectrum sources selected at 8.4 GHz and consisting of objects brighter than V= 17 is discussed. The sample was selected with three purposes in mind: (i) to find low-luminosity BL Lacertae (BL Lac) objects with radio luminosities comparable to those of BL Lacs selected at X-ray frequencies; (ii) to investigate the differences between BL Lacs and other flat radio spectrum sources; and (iii) to define a sample of nearby radio-loud objects, the host galaxies of which are easy to study. Using information on four observational parameters, radio polarization, optical percentage polarization, break contrast and equivalent width of the strongest emission line, we compare the properties of BL Lacs with those of other types of active galactic nuclei (AGN) found in the sample. We find that most of the objects have weak emission lines although some sources with Seyfert-type spectra were also found. With only a few exceptions, the two types of sources appear well separated in their observational properties. Among the objects studied we report 10 new BL Lacs and BL Lac candidates, and we define a 'complete' sample of bright flat radio spectrum sources that consists of those objects with redshift ≤ 0.1.

Original languageEnglish (US)
Pages (from-to)425-448
Number of pages24
JournalMonthly Notices of the Royal Astronomical Society
Volume281
Issue number2
DOIs
StatePublished - Jan 1 1996

Keywords

  • BL Lacertae objects: general
  • Galaxies: nuclei
  • Polarization
  • Radio continuum: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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