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arXiv · 1207.3592

On the redshift of the blazar PKS0447-439

Michele Fumagalli·Amy Furniss·John M. O'Meara·J. Xavier Prochaska·David A. Williams·Emanuele P. Farina
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Abstract

PKS0447-439 is one of the BL Lacertae objects that have been detected at very high energy. There has been a recent report of a lower limit of z>1.246 for the redshift of this blazar, challenging the current paradigm in which very high-energy gamma-rays cannot freely propagate in the z>1 universe. In this research note, we present a new MagE/Magellan spectrum of PKS0447-439 with exquisite signal-to-noise (S/N>150 at 6500A). Our analysis confirms the presence of the previously-reported absorption line at 6280A, which we identify, however, with a known telluric absorption, invalidating the claim that this blazar lies at z>1. Since no other extragalactic spectral features are detected, we cannot establish a redshift based on our spectrum.

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Michele Fumagalli, Amy Furniss, John M. O'Meara, J. Xavier Prochaska, David A. Williams, Emanuele P. Farina. 2012-07-16. On the redshift of the blazar PKS0447-439. https://doi.org/10.1051/0004-6361/201220022

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