The black hole masses and host galaxies of BL Lacertae objects

We have measured the central stellar velocity dispersion in the host galaxies of 11 BL Lac objects with redshifts zless than or equal to0.125. The range of velocity dispersions, similar to170-370 km s(-1), is similar to that of nearby radio galaxies. Using the correlation between stellar velocity dispersion and black hole mass defined for nearby galaxies, we derive estimates of the black hole masses in the range 10(7.9)-10(9.2) M-circle dot. We do not find any significant difference between the black hole masses in high-frequency peaked and low-frequency peaked BL Lac objects. Combining the velocity dispersions with previously measured host galaxy structural parameters, we find that the host galaxies lie on the fundamental plane of elliptical galaxies. This supports the conclusions of imaging studies that the majority of BL Lac hosts are normal giant elliptical galaxies.