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PKS 2123-463: a confirmed γ-ray blazar at high redshift


D'Ammando, F and Rau, A and Schady, P and Finke, J and Orienti, M and Greiner, J and Kann, DA and Ojha, R and Foley, AR and Stevens, J and Blanchard, JM and Edwards, PG and Kadler, M and Lovell, JEJ, PKS 2123-463: a confirmed γ-ray blazar at high redshift, Monthly Notices of the Royal Astronomical Society, 427, (1) pp. 893-900. ISSN 0035-8711 (2012) [Refereed Article]

Copyright Statement

Copyright 2012 The Authors Monthly Notices of the Royal Astronomical Society Copyright 2012 RAS

DOI: doi:10.1111/j.1365-2966.2012.22041.x


The flat spectrum radio quasar (FSRQ) PKS 2123−463 was associated in the first Fermi-Large Area Telescope (LAT) source catalogue with the γ-ray source 1FGL J2126.1−4603, but when considering the full first two years of Fermi observations, no γ-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 catalogue. On 2011 December 14 a γ-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, Gamma-ray Optical/Near-Infrared Detector (GROND), Australia Telescope Compact Array (ATCA), Ceduna and Seven Dishes Karoo Array Telescope (KAT-7) observatories. Results of the localization of the γ-ray source over 41 months of Fermi-LAT operation are reported here in conjunction with the results of the analysis of radio, optical, ultraviolet (UV) and X-ray data collected soon after the γ-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 γ-ray bands led to a firm identification of the γ-ray source with PKS 2123−463. A new photometric redshift has been estimated as z = 1.46 ± 0.05 using GROND and Swift Ultraviolet/Optical Telescope (UVOT) observations, in rough agreement with the disputed spectroscopic redshift of z = 1.67. We fit the broad-band spectral energy distribution with a synchrotron/external Compton model. We find that a thermal disc component is necessary to explain the optical/UV emission detected by Swift/UVOT. This disc has a luminosity of ∼1.8 × 1046 erg s−1, and a fit to the disc emission assuming a Schwarzschild (i.e. non-rotating) black hole gives a mass of ∼2 × 109 M⊙. This is the first black hole mass estimate for this source.

Item Details

Item Type:Refereed Article
Keywords:galaxies: active; galaxies: nuclei; quasars: general; quasars: individual: PKS 2123-463; gamma rays: general
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Blanchard, JM (Mr Jay Blanchard)
UTAS Author:Lovell, JEJ (Dr Jim Lovell)
ID Code:83102
Year Published:2012
Web of Science® Times Cited:8
Deposited By:Mathematics and Physics
Deposited On:2013-03-01
Last Modified:2017-11-01

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