NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2018-11-14 T01:27:05 PST
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For refcode 2014A&A...562A..64W:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2014A&A...562A..64W Why are some BL Lacertaes detected by Fermi, but others not? Wu, Zhongzu; Jiang, Dongrong; Gu, Minfeng; Chen, Liang Abstract. By cross-correlating an archival sample of 170 BL Lacs with a 2 year Fermi/LAT AGN sample, we have compiled a sample of 100 BL Lacs with Fermi detection (FBLs) and a sample of 70 non-Fermi BL Lacs (NFBLs). We compared various parameters of FBLs with those of NFBLs, including the redshift, the low-frequency radio luminosity at 408 MHz (L_408 MHz_), the absolute magnitude of host galaxies (M_host_), the polarization fraction from the NVSS survey (P_NVSS_), the observed arcsecond scale radio core flux at 5 GHz (F_core_), and the jet Doppler factor. All these parameters are directly measured or derived from available data in the literature. We found that the Doppler factor is on average greater in FBLs than in NFBLs, and the Fermi gamma-ray detection rate is higher in sources with higher Doppler factor. In contrast, there are no significant differences in terms of the intrinsic parameters of redshift, L_408 MHz_, M_host_, and P_NVSS_. FBLs seem to have a higher probability of exhibiting measurable proper motion. These results strongly indicate a stronger beaming effect in FBLs compared to NFBLs. The radio core flux is found to be strongly correlated with gamma-ray flux, which remains after excluding the common dependence of the Doppler factor. At the fixed Doppler factor, FBLs have systematically larger radio core flux than NFBLs, implying lower gamma-ray emission in NFBLs since the radio and gamma-ray flux are significantly correlated. Our results indicate that the Doppler factor is an important parameter of gamma-ray detection, that the non-detection of gamma-ray emission in NFBLs is probably due to low beaming and/or low intrinsic gamma-ray flux, and the gamma-rays are very likely produced cospatially with the arcsecond-scale radio core radiation and mainly through the SSC process. Tables 2, 3, and Fig. 6 are available in electronic form at http://www.aanda.org Key words: galaxies: active, BL Lacertae objects: general, galaxies: jets, galaxies: nuclei
Retrieve 170 NED objects in this reference.
Please click here for ADS abstract

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