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arXiv · 1209.4755

Redshift constraints for RGB 0136+391 and PKS 0735+178 from deep optical imaging

K. Nilsson·T. Pursimo·C. Villforth·E. Lindfors·L. O. Takalo·A. Sillanpää
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Abstract

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 r_eff = 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.

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K. Nilsson, T. Pursimo, C. Villforth, E. Lindfors, L. O. Takalo, A. Sillanpää. 2012-09-21. Redshift constraints for RGB 0136+391 and PKS 0735+178 from deep optical imaging. https://doi.org/10.1051/0004-6361/201219848

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