Continuum sources from the THOR survey between 1 and 2 GHz
MetadataShow full item record
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.
Showing items related by title, author, creator and subject.
Spectral properties and the effect on redshift cut-off of compact active galactic nuclei from the AT20G surveyChhetri, R.; Ekers, Ronald; Mahony, E.; Jones, P.; Massardi, M.; Ricci, R.; Sadler, E. (2012)Spectral index has been traditionally used to separate extragalactic radio sources into compact and extended populations, with the spectral transition placed variably between -0.4 and -0.6. We use high angular resolution ...
Shulevski, A.; Morganti, R.; Barthel, P.; Murgia, M.; Van Weeren, R.; White, G.; Brüggen, M.; Kunert-Bajraszewska, M.; Jamrozy, M.; Best, P.; Röttgering, H.; Chyzy, K.; De Gasperin, F.; Bîrzan, L.; Brunetti, G.; Brienza, M.; Rafferty, D.; Anderson, J.; Beck, R.; Deller, A.; Zarka, P.; Schwarz, D.; Mahony, E.; Orru, E.; Bell, M.; Bentum, M.; Bernardi, G.; Bonafede, A.; Breitling, F.; Broderick, J.; Butcher, H.; Carbone, D.; Ciardi, B.; De Geus, E.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M.; Grießmeier, J.; Gunst, A.; Heald, G.; Hoeft, M.; Hörandel, J.; Horneffer, A.; Van Der Horst, A.; Intema, Hubertus; Juette, E.; Karastergiou, A.; Kondratiev, V.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; McFadden, R.; McKay-Bukowski, D.; McKean, J.; Meulman, H.; Mulcahy, D.; Munk, H.; Norden, M.; Paas, H.; Pandey-Pommier, M.; Pizzo, R.; Polatidis, A.; Reich, W.; Rowlinson, A.; Scaife, A.; Serylak, M.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; Thoudam, S.; Toribio, M. (2015)Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio emission to large scales in the complex ...
Application of advanced techniques for the remote detection, modelling and spatial analysis of mesquite (prosopis spp.) invasion in Western AustraliaRobinson, Todd Peter (2008)Invasive plants pose serious threats to economic, social and environmental interests throughout the world. Developing strategies for their management requires a range of information that is often impractical to collect ...