The host galaxy of the BL Lacertae object 1ES 0647+250 and its imaging
  redshift
  Since no spectroscopic redshift is available for the remarkable BL Lac object
1ES 0647+250, we aim to derive an estimate of its distance from the properties
of its host galaxy.We obtained a deep, high-resolution near-infrared H-band
image of the BL Lacertae object 1ES 0647+250. We are able to detect the
underlying host galaxy in the near-infrared. The host galaxy has an H-band
magnitude of 16.9+-0.2 and an effective radius of 1.6+-0.3 arcsec. Using the
imaging redshift method by Sbarufatti et al. (2005), we estimate a redshift z =
0.41+-0.06. This redshift is consistent with the previously reported imaging
redshift estimate from the optical i'-band, z = 0.45+-0.08 by Meisner & Romani
(2010), and with previously reported lower limits for the redshift. It is also
in agreement with constraints from its gamma-ray emission. Imaging searches in
the near-infrared, even with moderately sized telescopes, for the host galaxies
of BL Lac objects at unknown redshift, are encouraged, as well as optical
spectroscopy of 1ES 0647+250 with large telescopes to determine its
spectroscopic redshift.
