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arXiv · 1509.08377

Redshift measurement of the BL-Lac gamma-ray blazar PKS 1424+240

A. C. Rovero·C. Donzelli·A. Pichel·H. Muriel
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Abstract

PKS 1424+240 is a BL-Lac blazar with unknown redshift detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. It was first detected at very-high-energy by VERITAS and latter confirmed by MAGIC. Attempts to find limits on its redshift include three estimations by modeling gamma-ray observations, and one obtained by analyzing Lyb and Lyg absorption lines observed in the far-UV spectra (from HST/COS) caused by absorbing gas along the line of sight. They allowed to constrain the redshift range to 0:6<z<1:19, which places PKS 1424+240 in the very interesting condition to be one of the few candidates to be the most distant blazars detected at very-high-energy gamma rays. Redshift determination of BL-Lac objects are difficult to achieve. We have found that redshift of blazars can be determined by its association to a galaxy group or cluster. To explore this possibility for PKS 1424+240, we have carried out spectroscopic measurements with the Gemini North telescope of galaxies in its field of view. In this work we present the optical spectrum of PKS 1424+240 and show preliminary results of the blazar environment characterization. Spectroscopic redshift using the optical spectrum of PKS 1424+240 could not be determined in this work.

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A. C. Rovero, C. Donzelli, A. Pichel, H. Muriel. 2015-09-28. Redshift measurement of the BL-Lac gamma-ray blazar PKS 1424+240. https://arxiv.org/abs/1509.08377

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