VizieR Online Data Catalog: SCORPIO field's study with ASKAP (Umana+, 2021)

A new era in radio astronomy has finally arrived. The Square Kilometre Array (SKA) precursors have started their early-science phase with impressive results that foreshadow their full operation. In particular the Australian SKA Array Pathfinder (ASKAP, Hotan et al. 2021PASA...38....9H) is transforming the way in which large radio surveys have been so far conducted. Due to the wide-field phased array feed (PAF) system (Chippendale, Hayman & Hay 2014PASA...31...19C) mounted on each antenna, ASKAP is capable of a huge instantaneous field of view.

A number of different regions of the sky were selected for testing the array in this phase: among these, one is centred towards the same field of the 'Stellar Continuum Originating from Radio Physics in Ourgalaxy' (SCORPIO) project (Umana et al. 2015MNRAS.454..902U, Cat. J/MNRAS/454/902). We will refer to this targeted observation as to the 'ASKAP SCORPIO observations'.

The SCORPIO field was observed with the ASKAP in band 1 (from 792 to 1032 MHz) in 2018 January using 15 antennas (of the 36 in the completed array) during the early-science phase. The array configuration had a minimum baseline of 22.4 m and a maximum baseline of 2.3 km. This implies that the observations, at the central frequency of 912 MHz, are sensitive to a minimum and maximum angular scale of 29.5 arcsec and 50 arcmin, respectively, (see section 2.1 The ASKAP observations).

The data reduction process used the ASKAPSOFT package, based on CASACORE and specifically optimized for managing the ASKAP data (Guzman et al. 2019ascl.soft12003G). The data reduction procedure is managed by a pipeline that configures and launches a series of jobs running on the Galaxy supercomputer at the Pawsey facility in Perth, (see section 2.2 Data reduction).

The last step of the askapsoft pipeline processing is an application of the source finder algorithm selavy (Whiting & Humphrey 2012PASA...29..371W) to create a compact source catalogue. SELAVY provides, for each fitted component, the peak and integrated flux densities, with their errors, the position angle, and the major and the minor FWHMs of the Gaussian component, indicating both the fit and its deconvolved value, given the image's restoring beam, (see section 3.1 Compact source extraction and preliminary validation).

The H II regions are found in star-forming sites, in the vicinity of high-mass stars, where the gas is ionized by ultraviolet photons from the central object. They are tracers of the current epoch star formation and their continuum radio emission is due to thermal Bremsstrahlung radiation. As anticipated (see section 3.3 Known Galactic sources), we produce the table2.dat for the 112 sources detected by visual inspection and extracted by SELAVY, (see section 3.3.1 H II regions).

(1 data file).