New Evidence for the Unified Scheme of Bl Lac Objects and Fri Radio Galaxies
نویسنده
چکیده
In this paper, we collect radio and X-ray observations for most Fanaroff-Riley I (FRI) radio galaxies in the Zirbel-Baum radio galaxy sample, and investigate the distribution of the radio-to-X-ray effective spectral index, αrx, to test the unified scheme of BL Lac objects and FRI radio galaxies. It is found that the range of αrx for FRI radio galaxies is almost the same as that for BL Lac objects, that the distribution of αrx probably peaks at the same position as BL Lac objects, and that the distribution of αrx for FRIs is similar to that for BL Lac objects. These suggest that there exist two subclasses of FRI radio galaxies: one is HBL-like, and the other is LBL-like, corresponding to high-energy-peaked (HBL) and low–energy-peaked (LBL) BL Lac objects, respectively. This result is consistent with previous VLA observations, and supports the unified scheme of BL Lac objects and FRI radio galaxies. Subject headings: BL Lac objects: general — galaxies: active — radiation mechanism: nonthermal — radio continuum: galaxies — X-rays: galaxies
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