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|Title:||Local Group dSph radio survey with ATCA (I): observations and background sources||Authors:||Regis, Marco
de Blok, W. J. G.
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||448||Issue:||4||First Page:||3731||Abstract:||Dwarf spheroidal (dSph) galaxies are key objects in near-field cosmology, especially in connection to the study of galaxy formation and evolution at small scales. In addition, dSphs are optimal targets to investigate the nature of dark matter. However, while we begin to have deep optical photometric observations of the stellar population in these objects, little is known so far about their diffuse emission at any observing frequency, and hence on thermal and non-thermal plasma possibly residing within dSphs. In this paper, we present deep radio observations of six local dSphs performed with the Australia Telescope Compact Array (ATCA) at 16 cm wavelength. We mosaicked a region of radius of about 1 deg around three `classical' dSphs, Carina, Fornax, and Sculptor, and of about half of degree around three `ultrafaint' dSphs, BootesII, Segue2, and Hercules. The rms noise level is below 0.05 mJy for all the maps. The restoring beams full width at half-maximum ranged from 4.2 arcsec × 2.5 arcsec to 30.0 arcsec × 2.1 arcsec in the most elongated case. A catalogue including the 1392 sources detected in the six dSph fields is reported. The main properties of the background sources are discussed, with positions and fluxes of brightest objects compared with the FIRST, NVSS, and SUMSS observations of the same fields. The observed population of radio emitters in these fields is dominated by synchrotron sources. We compute the associated source number counts at 2 GHz down to fluxes of 0.25 mJy, which prove to be in agreement with AGN count models.||Acknowledgments:||We thank Laura Bonavera for assisting with the C2499 ATCA observations of this project. We wish also to thank Mark Wieringa for the support on the miriad data reduction and Piero Ullio for insightful discussions during the early stages of the project. SC acknowledges support by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation and by the Square Kilometre Array (SKA). SP is partly supported by the US Department of Energy, Contract DE-FG02-04ER41268. MR acknowledges support by the research grant TAsP ( Theoretical Astroparticle Physics ) funded by the Istituto Nazionale di Fisica Nucleare (INFN). The ATCA is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.||URI:||http://hdl.handle.net/20.500.12386/30534||URL:||https://academic.oup.com/mnras/article/448/4/3731/954808||ISSN:||0035-8711||DOI:||10.1093/mnras/stu2747||Bibcode ADS:||2015MNRAS.448.3731R||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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