X-ray and radio follow-up observations of high-redshift blazar candidates in the Fermi-LAT unassociated source population

Y. Takahashi, Jun Kataoka, K. Niinuma, M. Honma, Y. Inoue, T. Totani, S. Inoue, T. Nakamori, Keiichi Maeda

    Research output: Contribution to journalArticle

    4 Citations (Scopus)

    Abstract

    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 2-8 keV < 1.37 × 10-14 erg cm-2 s-1. Radio observations at 6.7 GHz also result in an upper limit of S 6.7 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 γ = 1.8 and the unabsorbed flux is F 2-8 keV = 4.3 × 10-14 erg cm-2 s-1. Moreover, we detect unresolved radio emission at 6.7 GHz with flux S 6.7 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 ∼ 3-4.

    Original languageEnglish
    Article number36
    JournalAstrophysical Journal
    Volume773
    Issue number1
    DOIs
    Publication statusPublished - 2013 Aug 10

    Fingerprint

    radio
    radio observation
    x rays
    catalogs
    telescopes
    radio spectra
    blazars
    very long base interferometry
    astrometry
    erg
    radio emission
    very long baseline interferometry
    photons
    power law

    Keywords

    • galaxies: active
    • gamma rays: general
    • radiation mechanisms: non-thermal
    • X-rays: general

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    X-ray and radio follow-up observations of high-redshift blazar candidates in the Fermi-LAT unassociated source population. / Takahashi, Y.; Kataoka, Jun; Niinuma, K.; Honma, M.; Inoue, Y.; Totani, T.; Inoue, S.; Nakamori, T.; Maeda, Keiichi.

    In: Astrophysical Journal, Vol. 773, No. 1, 36, 10.08.2013.

    Research output: Contribution to journalArticle

    Takahashi, Y. ; Kataoka, Jun ; Niinuma, K. ; Honma, M. ; Inoue, Y. ; Totani, T. ; Inoue, S. ; Nakamori, T. ; Maeda, Keiichi. / X-ray and radio follow-up observations of high-redshift blazar candidates in the Fermi-LAT unassociated source population. In: Astrophysical Journal. 2013 ; Vol. 773, No. 1.
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    abstract = "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 2-8 keV < 1.37 × 10-14 erg cm-2 s-1. Radio observations at 6.7 GHz also result in an upper limit of S 6.7 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 γ = 1.8 and the unabsorbed flux is F 2-8 keV = 4.3 × 10-14 erg cm-2 s-1. Moreover, we detect unresolved radio emission at 6.7 GHz with flux S 6.7 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 ∼ 3-4.",
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    AU - Takahashi, Y.

    AU - Kataoka, Jun

    AU - Niinuma, K.

    AU - Honma, M.

    AU - Inoue, Y.

    AU - Totani, T.

    AU - Inoue, S.

    AU - Nakamori, T.

    AU - Maeda, Keiichi

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    N2 - 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 2-8 keV < 1.37 × 10-14 erg cm-2 s-1. Radio observations at 6.7 GHz also result in an upper limit of S 6.7 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 γ = 1.8 and the unabsorbed flux is F 2-8 keV = 4.3 × 10-14 erg cm-2 s-1. Moreover, we detect unresolved radio emission at 6.7 GHz with flux S 6.7 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 ∼ 3-4.

    AB - 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 2-8 keV < 1.37 × 10-14 erg cm-2 s-1. Radio observations at 6.7 GHz also result in an upper limit of S 6.7 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 γ = 1.8 and the unabsorbed flux is F 2-8 keV = 4.3 × 10-14 erg cm-2 s-1. Moreover, we detect unresolved radio emission at 6.7 GHz with flux S 6.7 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 ∼ 3-4.

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    KW - gamma rays: general

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    KW - X-rays: general

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