Chandra observations and classification of active galactic nucleus candidates correlated with auger UHECRs

William A. Terrano, Ingyin Zaw, Glennys R. Farrar

    Research output: Contribution to journalArticle

    Abstract

    We report on Chandra X-ray observations of possible active galactic nuclei (AGNs) which have been correlated with ultrahigh energy cosmic rays (UHECRs) observed by the Pierre Auger Collaboration. Combining our X-ray observations with optical observations, we conclude that one-third of the 21 Veron-Cetty Veron (VCV) galaxies correlating with UHECRs in the first Auger data release are actually not AGNs. We review existing optical observations of the 20 VCV galaxies correlating with UHECRs in the second Auger data release and determine that three of them are not AGNs and two are uncertain. Overall, of the 57 published UHECRs with |b| > 10°, 22 or 23 correlate with true AGNs using the Auger correlation parameters. We also measured the X-ray luminosity of ESO139-G12 to complete the determination of the bolometric luminosities of AGNs correlating with UHECRs in the first data set. Apart from two candidate sources which require further observation, we determined bolometric luminosities for the candidate galaxies of the second data set. We find that only 2 of the total of 69 published UHECRs correlate with AGNs (IC5135 and IC4329a) which are powerful enough in their steady state to accelerate protons to the observed energies of their correlated UHECRs. The GZK expectation is that 45% of the sources of UHECRs above 60 EeV should be contained within the z < 0.018 volume defined by the Auger scan analysis, so an observed level of 30%-50% correlation with weak AGNs is compatible with the suggestion that AGNs experience transient high-luminosity states during which they accelerate UHECRs.

    Original languageEnglish (US)
    Article number142
    JournalAstrophysical Journal
    Volume754
    Issue number2
    DOIs
    StatePublished - Aug 1 2012

    Fingerprint

    active galactic nuclei
    cosmic ray
    cosmic rays
    energy
    luminosity
    galaxies
    x rays
    suggestion
    protons

    Keywords

    • cosmic rays
    • galaxies: active
    • X-rays: galaxies

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Chandra observations and classification of active galactic nucleus candidates correlated with auger UHECRs. / Terrano, William A.; Zaw, Ingyin; Farrar, Glennys R.

    In: Astrophysical Journal, Vol. 754, No. 2, 142, 01.08.2012.

    Research output: Contribution to journalArticle

    Terrano, William A. ; Zaw, Ingyin ; Farrar, Glennys R. / Chandra observations and classification of active galactic nucleus candidates correlated with auger UHECRs. In: Astrophysical Journal. 2012 ; Vol. 754, No. 2.
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    abstract = "We report on Chandra X-ray observations of possible active galactic nuclei (AGNs) which have been correlated with ultrahigh energy cosmic rays (UHECRs) observed by the Pierre Auger Collaboration. Combining our X-ray observations with optical observations, we conclude that one-third of the 21 Veron-Cetty Veron (VCV) galaxies correlating with UHECRs in the first Auger data release are actually not AGNs. We review existing optical observations of the 20 VCV galaxies correlating with UHECRs in the second Auger data release and determine that three of them are not AGNs and two are uncertain. Overall, of the 57 published UHECRs with |b| > 10°, 22 or 23 correlate with true AGNs using the Auger correlation parameters. We also measured the X-ray luminosity of ESO139-G12 to complete the determination of the bolometric luminosities of AGNs correlating with UHECRs in the first data set. Apart from two candidate sources which require further observation, we determined bolometric luminosities for the candidate galaxies of the second data set. We find that only 2 of the total of 69 published UHECRs correlate with AGNs (IC5135 and IC4329a) which are powerful enough in their steady state to accelerate protons to the observed energies of their correlated UHECRs. The GZK expectation is that 45{\%} of the sources of UHECRs above 60 EeV should be contained within the z < 0.018 volume defined by the Auger scan analysis, so an observed level of 30{\%}-50{\%} correlation with weak AGNs is compatible with the suggestion that AGNs experience transient high-luminosity states during which they accelerate UHECRs.",
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