Are there two populations of Bl-Lacertae objects

1993. Are there two populations of Bl-Lacertae objects. Monthly Notices of the Royal Astronomical Society 264 (4) , p. 919.

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Abstract

We present single-epoch infrared photometry of two complete samples of BL Lacertae objects, one radio-selected (RBLs) and one X-ray-selected (XBLs). we find that the RBLs fall into two distinct groups on the (J - H)-( H - K) plane, corresponding to those sources in which the host galaxy makes a significant contribution to the infrared colours and those with higher redshift whose infrared spectra are dominated by power-law non-thermal emission. We also find that the XBLs have colours intermediate between these two groups (although with significant scatter). We show that the infrared colours of Fanaroff-Riley class 1 galaxies (FR1), XBLs and RBLs are consistent with mixing of stellar emission with an increasing proportion of non-thermal emission, and argue that the FR1s, XBLs and RBLs form part of a single population, with the FR1s and XBLs both being at larger angles to the line of sight than are the RBLs, and differing only in the luminosities of their non-thermal components.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Publisher:	Wiley-Blackwell
ISSN:	0035-8711
Related URLs:	http://adsabs.harvard.edu/abs/1993MNRAS....
Last Modified:	21 Oct 2022 09:21
URI:	https://orca.cardiff.ac.uk/id/eprint/36072

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