Abstract
view Abstract Citations (77) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Fanaroff-Riley I Galaxies as the Parent Population of BL Lacertae Objects. II. Optical Constraints Padovani, Paolo ; Urry, C. Megan Abstract As part of a continuing investigation of the hypothesis that BL Lacertae objects are low-luminosity radio galaxies with relativistic jets pointing along the line of sight, we consider the number density of these objects at optical wavelengths. There are no well-defined optical samples of BL Lacertae objects, but, using existing catalogs of active galactic nuclei, we obtain new estimates of the optical counts and luminosity function of BL Lacertae objects that are not inconsistent with the beaming hypothesis. Our calculations depend primarily on observed quantities, including the optical luminosity function of the assumed parent population, Fanaroff-Riley type I (FR I) galaxies. Although FR I galaxies have relatively low radio luminosities, they are bright optical galaxies and their luminosity function is very steep. We extend the formalism of Urry and Shafer for comparing beamed and parent populations to cases, such as the optical one, where galaxy light represents a substantial fraction of the total luminosity. The Lorentz factor of the optical jet is estimated to be roughly in the range 8 < γ_0_ < 20, larger than the X-ray value, γ_x_ ~ 3, found by Padovani and Urry. Since currently observed BL Lacertae objects already have luminosities below the predicted break in the luminosity function, itself a signature of beaming, a definite test of the beaming hypothesis does not depend on more sensitive surveys (in contrast to the X-ray case); it simply requires a sizable optically selected sample of BL Lacertae objects. Publication: The Astrophysical Journal Pub Date: February 1991 DOI: 10.1086/169701 Bibcode: 1991ApJ...368..373P Keywords: Bl Lacertae Objects; Galactic Structure; Radio Galaxies; Active Galactic Nuclei; Astronomical Catalogs; Astronomical Models; Luminosity; Astrophysics; BL LACERTAE OBJECTS; GALAXIES: JETS; GALAXIES: NUCLEI; RADIO SOURCES: GALAXIES full text sources ADS | Related Materials (2) Part 1: 1990ApJ...356...75P Part 3: 1991ApJ...382..501U
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