Radio luminosities and classificatory criteria of BL Lacertae objects

D. C. Mei; L. Zhang; Z. J. Jiang

doi:10.1051/0004-6361:20020969

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Volume 391 / No 3 (September I 2002)

A&A, 391 3 (2002) 917-922

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Issue		A&A Volume 391, Number 3, September I 2002


Page(s)		917 - 922
Section		Cosmology (including clusters of galaxies)
DOI		https://doi.org/10.1051/0004-6361:20020969
Published online		09 August 2002

A&A 391, 917-922 (2002)

Research Note

Radio luminosities and classificatory criteria of BL Lacertae objects

D. C. Mei, L. Zhang and Z. J. Jiang

Department of Physics, Yunnan University, Kunming 650091, PR China

Corresponding author: D. C. Mei, kmdcmei@public.km.yn.cn

Received: 17 April 2002
Accepted: 26 June 2002

Abstract

Using the sample of radio-selected BL Lacertae objects (RBLs) and X-ray selected BL Lacertae objects (XBLs) presented by Sambruna et al. ([CITE]), we calculated the luminosities in radio, optical and X-ray of each source and made a statistical analysis among the luminosities at different wave-bands, broad-band spectral indices from radio to X-ray ( $\alpha_{\rm rx}$ ) and peak frequencies ( $\nu_{\rm p}$ ). Our results are as follows: (i) there is a positive correlation between radio luminosity L_r and $\alpha_{\rm rx}$ and a negative correlation between L_r and $\nu_{\rm p}$ . High-energy peak BL Lacs (HBLs) and low-energy peak BL Lacs (LBLs) can be distinguished very well; the dividing lines are probably those of $\log {L_{\rm r}}=43.25$ (erg/s) and $\alpha_{\rm rx}>$ (or $\leq$ )0.75 for $\log L_{\rm r}$ – $\alpha_{\rm rx}$ plot and those of $\log L_{\rm r}\leq 43.25$ (erg/s) and $\log {\nu_{\rm p}}>14.7$ for the ${\bf\log}\,L_{\rm r}$ – ${\bf\log}\,\nu_{\rm p}$ plot; (ii) there is a weak positive correlation between optical luminosity L_o and $\alpha_{\rm rx}$ and a negative weak correlation between $L_{\rm o}$ and $\nu_{\rm p}$ ; (iii) there is no correlation between X-ray luminosity L_x and $\alpha_{\rm rx}$ or between L_x and $\nu_{\rm p}$ . From our analysis, we find that synchrotron radiation is the main X-ray radiation mechanism for HBLs while inverse Compton scattering is dominant for LBLs.

Key words: galaxies: BL Lacertae objects: general / galaxies: fundamental parameters / radiation mechanism: non–thermal

© ESO, 2002

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