SIMBAD references

2016MNRAS.458.2836P - Mon. Not. R. Astron. Soc., 458, 2836-2839 (2016/May-3)

On the redshift of the very high-energy gamma-ray BL Lac object S2 0109+22.


Abstract (from CDS):

The determination of the redshift of extragalactic gamma-ray sources is of fundamental importance for the interpretation of their emission models and extragalactic population studies, active galactic nuclei classification schemes, and to study the interaction with the extragalactic background light. Here we focus on the BL Lac S2 0109+22, recently detected at very high energies. We obtained a high signal-to-noise optical spectrum at Gran Telescopio Canarias for the source over the spectral range 4000-10 000 Å, to search for spectral features of the host galaxy and/or of the nuclear source and it was compared with previous observations in order to confirm and/or dispute its redshift determination. We find the S2 0109+22 optical spectrum is well represented by a power-law continuum without any absorption or emission feature of equivalent width >0.1 Å. Based on the new optical spectrum, we are able to set a redshift lower limit z > 0.35, assuming the source is hosted by a massive elliptical galaxy typical for this class of sources. The redshift z=0.265 proposed in the literature for this object is most probably referred to a r=18.3 galaxy at 15 arcsec from S2 0109. This galaxy could belong to a group of faint galaxies located at z ∼ 0.26.

Abstract Copyright: © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): BL Lacertae objects: individual - galaxies: distances and redshifts

Simbad objects: 4

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