New Evidence for the Unified Scheme of BL Lacertae Objects and FR I Radio Galaxies

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Abstract
In this paper, we collect radio and X-ray observations for most Fanaroff-Riley I (FR I) 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 FR I radio galaxies. It is found that the range of αrx for FR I 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 FR I galaxies is similar to that for BL Lac objects. These suggest that there exist two subclasses of FR I 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 FR I radio galaxies.
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