Multi-band near-infrared images of twelve BL Lacertae objects were obtained with the 2.5m telescope at the Las Campanas Observatory in order to determine the properties of their underlying host galaxies .
Resolved emission was clearly detected in eight of the lowest redshift targets ( up to z \sim 0.3 ) , and was modeled with a de Vaucouleurs r ^ { 1 / 4 } surface brightness law .
We find that the morphologies match the elliptical galaxy profiles well , and that the BL Lac objects reside in large and luminous , but otherwise normal hosts – consistent with previous studies done predominantly at optical wavelengths .
The median absolute K-band magnitude of the galaxies in this study is –26.2 , the average half-light radius is 4.2 \pm 2.3 kpc , and their average integrated R - K color is 2.7 \pm 0.3 mag .
These are well within the range of values measured previously in the H-band by Kotilainen et al .
and Scarpa et al .
in a comparable number of targets .
Taking their data together with our results , we find a best-fit K-band Kormendy relation of \mu _ { e } = 4.3 log _ { 10 } ( r _ { e } /kpc ) +14.2 mag arcsec ^ { -2 } , virtually identical to that obtained for normal ellipticals .
Finally , the near-infrared colors determined for five galaxies ( average J - K = 0.8 \pm 0.3 mag ) are the first such measurements for BL Lac hosts , and match those expected from old stellar populations at the BL Lac redshifts .