Evolutionary Map of the Universe (EMU):Compact radio sources in the SCORPIO field towards the Galactic plane

Abstract

We present observations of a region of the Galactic plane taken during the Early Science Program of the Australian Square Kilometre Array Pathfinder (ASKAP). In this context, we observed the SCORPIO field at 912 MHz with an uncompleted array consisting of 15 commissioned antennas. The resulting map covers a square region of ~40 deg^2, centred on (l, b)=(343.5°, 0.75°), with a synthesized beam of 24"x21" and a background rms noise of 150-200 μJy/beam, increasing to 500-600 μJy/beam close to the Galactic plane. A total of 3963 radio sources were detected and characterized in the field using the CAESAR source finder. We obtained differential source counts in agreement with previously published data after correction for source extraction and characterization uncertainties, estimated from simulated data. The ASKAP positional and flux density scale accuracy were also investigated through comparison with previous surveys (MGPS, NVSS) and additional observations of the SCORPIO field, carried out with ATCA at 2.1 GHz and 10" spatial resolution. These allowed us to obtain a measurement of the spectral index for a subset of the catalogued sources and an estimated fraction of (at least) 8% of resolved sources in the reported catalogue. We cross-matched our catalogued sources with different astronomical databases to search for possible counterparts, finding ~150 associations to known Galactic objects. Finally, we explored a multiparametric approach for classifying previously unreported Galactic sources based on their radio-infrared colors.

31 pages, 15 figures, 15 tables

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• The Rapid ASKAP Continuum Survey IV: continuum imaging at 1367.5 MHz and the first data release of RACS-mid
• The ASKAP-EMU Early Science Project: 888 MHz Radio Continuum Survey of the Large Magellanic Cloud
• GASKAP Pilot Survey Science II: ASKAP Zoom Observations of Galactic 21-cm Absorption
• Scalable precision wide-field imaging in radio interferometry: I. uSARA validated on ASKAP data
• Two Extreme Steep-Spectrum, Polarized Radio Sources Towards the Galactic Bulge
• The SARAO MeerKAT Galactic Plane Survey extended source catalogue
• Hydra I: An extensible multi-source-finder comparison and cataloguing tool
• Transformer-Based Source Detection and Morphological Classification in LOFAR Deep-Field Continuum Images
• Sifting the debris: Patterns in the SNR population with unsupervised ML methods