SCORPIO - II. Spectral indices of weak Galactic radio sources
| Autor: | A. Ingallinera, L. Cerrigone, Simone Riggi, F. Cavallaro, P. Leto, C. Agliozzo, Thomas M. O. Franzen, C. S. Buemi, Filomena Bufano, G. Umana, J. Marvil, Ray P. Norris, C. Trigilio |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Astrophysics::High Energy Astrophysical Phenomena
Population FOS: Physical sciences galaxies [Radio continuum] Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences 0103 physical sciences stellar content [Galaxy] education 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Astrophysics::Galaxy Astrophysics Physics High Energy Astrophysical Phenomena (astro-ph.HE) Spectral index education.field_of_study 010308 nuclear & particles physics Astronomy and Astrophysics Thermal emission Galactic plane Rms noise ISM [Radio continuum] Astrophysics - Astrophysics of Galaxies Planetary nebula Square degree Stars Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) interferometric [Techniques] stars [Radio continuum] Astrophysics - High Energy Astrophysical Phenomena |
| Popis: | In the next few years the classification of radio sources observed by the large surveys will be a challenging problem, and spectral index is a powerful tool for addressing it. Here we present an algorithm to estimate the spectral index of sources from multiwavelength radio images. We have applied our algorithm to SCORPIO (Umana et al. 2015), a Galactic Plane survey centred around 2.1 GHz carried out with ATCA, and found we can measure reliable spectral indices only for sources stronger than 40 times the rms noise. Above a threshold of 1 mJy, the source density in SCORPIO is 20 percent greater than in a typical extra-galactic field, like ATLAS (Norris et al. 2006), because of the presence of Galactic sources. Among this excess population, 16 sources per square degree have a spectral index of about zero, suggesting optically thin thermal emission such as Hii regions and planetary nebulae, while 12 per square degree present a rising spectrum, suggesting optically thick thermal emission such as stars and UCHii regions. Comment: 12 pages, 11 figures, accepted by MNRAS |
| Databáze: | OpenAIRE |
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