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

In this paper, we collect radio and X-ray observations for mostFanaroff-Riley I (FRI) radio galaxies in the Zirbel-Baum radio galaxy sample,and investigate the distribution of the radio-to-X-ray effective spectralindex, $\alpha_{rx}$, to test the unified scheme of BL Lac objects and FRIradio galaxies. It is found that the range of $\alpha_{rx}$ for FRI radiogalaxies is almost the same as that for BL Lac objects, that the distributionof $\alpha_{rx}$ probably peaks at the same position as BL Lac objects, andthat the distribution of $\alpha_{rx}$ for FRIs is similar to that for BL Lacobjects. 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 isconsistent with previous VLA observations, and supports the unified scheme ofBL Lac objects and FRI radio galaxies.Comment: 5 pages, 1 figur