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Title: X-RAY AND RADIO FOLLOW-UP OBSERVATIONS OF HIGH-REDSHIFT BLAZAR CANDIDATES IN THE FERMI-LAT UNASSOCIATED SOURCE POPULATION

We report on the results of X-ray and radio follow-up observations of two GeV gamma-ray sources 2FGL J0923.5+1508 and 2FGL J1502.1+5548, selected as candidates for high-redshift blazars from unassociated sources in the Fermi Large Area Telescope Second Source Catalog. We utilize the Suzaku satellite and the VLBI Exploration of Radio Astrometry (VERA) telescopes for X-ray and radio observations, respectively. For 2FGL J0923.5+1508, a possible radio counterpart NVSS J092357+150518 is found at 1.4 GHz from an existing catalog, but we do not detect any X-ray emission from it and derive a flux upper limit F{sub 2-8{sub keV}} < 1.37 Multiplication-Sign 10{sup -14} erg cm{sup -2} s{sup -1}. Radio observations at 6.7 GHz also result in an upper limit of S{sub 6.7{sub GHz}} < 19 mJy, implying a steep radio spectrum that is not expected for a blazar. On the other hand, we detect X-rays from NVSS J150229+555204, the potential 1.4 GHz radio counterpart of 2FGL J1502.1+5548. The X-ray spectrum can be fitted with an absorbed power-law model with a photon index {gamma} = 1.8{sup +0.3}{sub -0.2} and the unabsorbed flux is F{sub 2-8{sub keV}} = 4.3{sup +1.1}{sub -1.0} Multiplication-Sign 10{sup -14} erg cm{sup -2} s{sup -1}. Moreover, we detect unresolved radiomore » emission at 6.7 GHz with flux S{sub 6.7{sub GHz}} = 30.1 mJy, indicating a compact, flat-spectrum radio source. If NVSS J150229+555204 is indeed associated with 2FGL J1502.1+5548, then we find that its multiwavelength spectrum is consistent with a blazar at redshift z {approx} 3-4.« less
Authors:
; ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 Japan (Japan)
  2. Department of Physics, Faculty of Science, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8512 (Japan)
  3. Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
  4. Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
  5. Department of Astronomy, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
  6. Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)
Publication Date:
OSTI Identifier:
22140270
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 773; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CATALOGS; COSMIC GAMMA SOURCES; EMISSION; EXPLORATION; GALAXIES; GAMMA RADIATION; GEV RANGE; GHZ RANGE; PHOTONS; RED SHIFT; TELESCOPES; X RADIATION; X-RAY SPECTRA