The host galaxy of the BL Lacertae object 1ES 0647+250 and its imaging redshift

TL;DR

This study estimates the redshift of the BL Lac object 1ES 0647+250 by analyzing its host galaxy's properties in near-infrared imaging, providing a new distance estimate consistent with previous methods and constraints.

Contribution

The paper introduces a near-infrared imaging method to estimate the redshift of BL Lac objects lacking spectroscopic data, demonstrating its effectiveness for 1ES 0647+250.

Findings

Estimated redshift z = 0.41+-0.06 from near-infrared imaging

Host galaxy detected with H-band magnitude 16.9+-0.2

Redshift estimate consistent with optical and gamma-ray constraints

Abstract

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.