Issue |
A&A
Volume 547, November 2012
|
|
---|---|---|
Article Number | A1 | |
Number of page(s) | 6 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201219848 | |
Published online | 19 October 2012 |
Research Note
Redshift constraints for RGB 0136+391 and PKS 0735+178 from deep optical imaging⋆
1
Finnish Centre for Astronomy with ESO (FINCA), University of
Turku, Väisäläntie
20, 21500
Piikkiö,
Finland
e-mail: kani@utu.fi
2
Nordic Optical Telescope, Apartado 474,
38700
Santa Cruz de La Palma,
Spain
3
Department of Astronomy, University of Florida,
211 Bryant Space Science Center,
Gainesville, FL
32611-2055,
USA
4
Tuorla Observatory, Department of Physics and Astronomy,
University of Turku, Väisäläntie
20, 21500
Piikkiö,
Finland
Received: 20 June 2012
Accepted: 13 September 2012
We present the results of deep I-band imaging of two BL Lacerate objects, RGB 0136+391 and PKS 0735+178, during an epoch when the optical nucleus was in a faint state in both targets. In PKS 0735+178 we find a significant excess over a point source, which, if fitted by the de Vaucouleurs model, corresponds to a galaxy with I = 18.64 ± 0.11 and reff = 1.8 ± 0.4 arcsec. Interpreting this galaxy as the host galaxy of PKS 0735+178 we derive z = 0.45 ± 0.06 using the host galaxy as a “standard candle”. We also discuss the immediate optical environment of PKS 0735+178 and the identity of the MgII absorber at z = 0.424. Despite of the optimally chosen epoch and deep imaging we find the surface brightness profile of RGB 0136+391 to be consistent with a point source. By determining a lower limit for the host galaxy brightness by simulations, we derive z > 0.40 for this target.
Key words: galaxies: active / galaxies: nuclei / BL Lacertae objects: individual: RGB 0136+391 / BL Lacertae objects: individual: PKS 0735+178
© ESO, 2012
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