Redshift of the Blazar KUV 00311-193: Modeling the EBL Absorption

A. PICHEL; A.C. ROVERO; M. FERNANDEZ ALONSO, VERITAS COLLABORATION: A.C. ROVERO

Madison

Conferencia; 36th International Cosmic Ray Conference; 2019

University of Wisconsin

AGNs are believed to be the source of very energetic cosmic rays which, in turn, produce gammarays throughout the interactions with matter. Therefore, the study of their very-high-energy(VHE) gamma-ray spectra is fundamental to understand the cosmic-ray acceleration mechanismsin these objects. Blazars are the type of AGNs populating gamma-ray catalogs so we will con-centrate on studying these objects, and specially BL Lacs, which have a featureless or very weakemission/absorption lines spectra. Given that the extragalactic VHE gamma-ray catalog is poorlypopulated (about 70 blazars), having a redshift estimation of every single source is important forthe study of cosmic rays origin. In this work we use EBL absorption as a tool to estimate KUV00311-1938 redshift by comparing HE gamma-ray observations with modeled EBL absorbed fluxpoints. KUV 00311-1938 is a very interesting BL-Lac; a priori it can be one of the most distantblazars since it has an estimated redshift in the range 0.5 to 1.54. Assuming that there is nospectral cutoff, we consider the intrinsic VHE spectrum to be the extrapolation of the Fermi-LATspectrum and model the intergalactic absorption by using the main current EBL models. Compar-ing these results with the VHE measured point by H.E.S.S., we give an estimate for the redshiftof the blazar within observation errors.