PKS 2123-463: a confirmed gamma-ray blazar at high redshift
Abstract
The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the First Fermi-LAT source catalog with the gamma-ray source 1FGL J2126.1-4603, but when considering the full first two years of Fermi observations, no gamma-ray source at a position consistent with this FSRQ was detected, and thus PKS 2123-463 was not reported in the Second Fermi-LAT source catalog. On 2011 December 14 a gamma-ray source positionally consistent with PKS 2123-463 was detected in flaring activity by Fermi-LAT. This activity triggered radio-to-X-ray observations by the Swift, GROND, ATCA, Ceduna, and KAT-7 observatories. Results of the localization of the gamma-ray source over 41 months of Fermi-LAT operation are reported here in conjunction with the results of the analysis of radio, optical, UV and X-ray data collected soon after the gamma-ray flare. The strict spatial association with the lower energy counterpart together with a simultaneous increase of the activity in optical, UV, X-ray and gamma-ray bands led to a firm identification of the gamma-ray source with PKS 2123-463. A new photometric redshift has been estimated as z = 1.46+/-0.05 using GROND and Swift/UVOT observations, in rough agreement with the disputed spectroscopic redshift of z = 1.67. We fit the broadband spectral energy distribution with a synchrotron/external Compton model. We find that a thermal disk component is necessary to explain the optical/UV emission detected by Swift/UVOT. This disk has a luminosity of about 1.8x10^46 erg/s, and a fit to the disk emission assuming a Schwarzschild (i.e., nonrotating) black hole gives a mass of about 2x10^9 solar masses. This is the first black hole mass estimate for this source.
Keywords
Cite
@article{arxiv.1209.0479,
title = {PKS 2123-463: a confirmed gamma-ray blazar at high redshift},
author = {F. D'Ammando and A. Rau and P. Schady and J. Finke and M. Orienti and J. Greiner and D. A. Kann and R. Ojha and A. R. Foley and J. Stevens and J. M. Blanchard and P. G. Edwards and M. Kadler and J. E. J. Lovell},
journal= {arXiv preprint arXiv:1209.0479},
year = {2015}
}
Comments
9 pages, 5 figures, 5 tables. Accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1207.3092