2011A&A...534L...2K

Since no spectroscopic redshift is available for the remarkable BL Lacertae object (BL Lac) 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 Lac 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." Using the imaging redshift method developed by Sbarufatti and collaborators, 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 of z=0.45±0.08, and with previously reported lower limits to the redshift. It agrees with constraints from its gamma-ray emission. We encourage imaging searches in the near-infrared, even with moderately sized telescopes, of the host galaxies of BL Lac objects at unknown redshift, as well as optical spectroscopy studies of 1ES 0647+250 with large telescopes to determine its spectroscopic redshift.