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    Continuum sources from the THOR survey between 1 and 2 GHz

    Access Status
    Open access via publisher
    Authors
    Bihr, S.
    Johnston, K.
    Beuther, H.
    Anderson, L.
    Ott, J.
    Rugel, M.
    Bigiel, F.
    Brunthaler, A.
    Glover, S.
    Henning, T.
    Heyer, M.
    Klessen, R.
    Linz, H.
    Longmore, S.
    McClure-Griffiths, N.
    Menten, K.
    Plume, R.
    Schierhuber, T.
    Shanahan, R.
    Stil, J.
    Urquhart, J.
    Walsh, Andrew
    Date
    2016
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Bihr, S. and Johnston, K. and Beuther, H. and Anderson, L. and Ott, J. and Rugel, M. and Bigiel, F. et al. 2016. Continuum sources from the THOR survey between 1 and 2 GHz. Astronomy and Astrophysics. 588.
    Source Title
    Astronomy and Astrophysics
    DOI
    10.1051/0004-6361/201527697
    ISSN
    0004-6361
    School
    Curtin Institute of Radio Astronomy (Physics)
    URI
    http://hdl.handle.net/20.500.11937/25661
    Collection
    • Curtin Research Publications
    Abstract

    We carried out a large program with the Karl G. Jansky Very Large Array (VLA): "THOR: The H1, OH, Recombination line survey of the Milky Way". We observed a significant portion (~100 deg2) of the Galactic plane in the first quadrant of the Milky Way in the 21 cm H I line, 4 OH transitions, 19 radio recombination lines, and continuum from 1 to 2 GHz. In this paper we present a catalog of the continuum sources in the first half of the survey (l = 14.0-37.9° and l = 47.1-51.2°, | b | = 1.1°) at a spatial resolution of 10.25", depending on the frequency and sky position with a spatially varying noise level of ~0.3.1 mJy beam-1. The catalog contains ~4400 sources. Around 1200 of these are spatially resolved, and ~1000 are possible artifacts, given their low signaltonoise ratios. Since the spatial distribution of the unresolved objects is evenly distributed and not confined to the Galactic plane, most of them are extragalactic. Thanks to the broad bandwidth of the observations from 1 to 2 GHz, we are able to determine a reliable spectral index for ~1800 sources. The spectral index distribution reveals a doublepeaked profile with maxima at spectral indices of a ˜-1 and a ˜ 0, corresponding to steep declining and flat spectra, respectively. This allows us to distinguish between thermal and nonthermal emission, which can be used to determine the nature of each source. We examine the spectral index of ~300 known HII regions, for which we find thermal emission with spectral indices around a˜ 0. In contrast, supernova remnants (SNR) show nonthermal emission with a ˜-0.5 and extragalactic objects generally have a steeper spectral index of a ˜-1. Using the spectral index information of the THOR survey, we investigate potential SNR candidates. We classify the radiation of four SNR candidates as nonthermal, and for the first time, we provide strong evidence for the SNR origin of these candidates.

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