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Paper: The Host Galaxies of BL Lac Objects in the Near-Infrared
Volume: 159, BL Lac Phenomenon
Page: 399
Authors: Kotilainen, J. K.
Abstract: Results from high resolution near--infrared imaging of 20 flat spectrum radio quasars (FSRQ; median z =3D 0.65) and 11 BL Lac objects (median z =3D 0.19) are presented. The host galaxy is clearly detected in 6 FSRQs and 7 BL Lacs, and marginally in 6 other FSRQs. The hosts of BL Lacs and FSRQs are luminous (M(H) =3D --26 and --27, respectively), 1--2 mag brighter than a typical field galaxy L^*, and 0--1 mag brighter than brightest cluster galaxies. FSRQ hosts are intermediate between those of low and high z radio--loud quasars (M(H) =3D --26 and --29, respectively), in good agreement with unified models. Optical/near--infrared colour and colour gradient of the BL Lac hosts are similar to those of normal ellipticals, indicating that the nuclear activity has little effect on the host properties. The nucleus--to--galaxy luminosity ratio of BL Lacs is similar to that of low z radio galaxies, but smaller than that of FSRQs, suggesting a difference in the intrinsic nuclear brightness or in the Doppler beaming factor between the two types of blazars.
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