Abstract
ABSTRACT We present an analysis of a new 120 deg2 radio continuum image of the Large Magellanic Cloud (LMC) at 888 MHz with a bandwidth of 288 MHz and beam size of 13${_{.}^{\prime\prime}}$9 × 12${_{.}^{\prime\prime}}$1 from the Australian Square Kilometre Array Pathfinder processed as part of the Evolutionary Map of the Universe survey. The median root mean squared noise is 58 $\mu$Jy beam−1. We present a catalogue of 54 612 sources, divided over a Gold list (30 866 sources) complete down to 0.5 mJy uniformly across the field, a Silver list (22 080 sources) reaching down to <0.2 mJy, and a Bronze list (1666 sources) of visually inspected sources in areas of high noise and/or near bright complex emission. We discuss detections of planetary nebulae and their radio luminosity function, young stellar objects showing a correlation between radio luminosity and gas temperature, novae and X-ray binaries in the LMC, and active stars in the Galactic foreground that may become a significant population below this flux level. We present examples of diffuse emission in the LMC (H ii regions, supernova remnants, bubbles) and distant galaxies showcasing spectacular interaction between jets and intracluster medium. Among 14 333 infrared counterparts of the predominantly background radio source population, we find that star-forming galaxies become more prominent below 3 mJy compared to active galactic nuclei. We combine the new 888 MHz data with archival Australia Telescope Compact Array data at 1.4 GHz to determine spectral indices; the vast majority display synchrotron emission but flatter spectra occur too. We argue that the most extreme spectral index values are due to variability.
Highlights
The Large Magellanic Cloud (LMC) is a disrupted barred spiral galaxy interacting with the Milky Way and its nearest neighbour, the Small Magellanic Cloud
Two radio continuum images from the Australian Square Kilometre Array Pathfinder (ASKAP) survey in the direction of the SMC were taken as part of the Evolutionary Map of the Universe (EMU) Early Science Project (ESP) survey of the Magellanic Clouds (Joseph et al 2019)
We present the 888 MHz ASKAP EMU ESP radio continuum survey of the LMC
Summary
The Large Magellanic Cloud (LMC) is a disrupted barred spiral galaxy interacting with the Milky Way and its nearest neighbour, the Small Magellanic Cloud. Multi-wavelength surveys from X-ray to far-infrared (far-IR) combined with the new EMU ASKAP data provide a prime opportunity to study a large population of high redshift AGN in the direction of the LMC. We present a new source catalogue from the ASKAP ESP for radio point sources observed towards the LMC, obtained from a mosaic of images taken at 888 MHz (λ = 34 cm). Additional uncertainties are introduced by point spread function (PSF) variation in a mosaic, generally ∼ 1–2 per cent for long-track observations such as this one In later observations this is alleviated by convolving each beam image to the smallest possible common PSF (McConnell et al 2020). Testing proved that for a large variety of regions, containing from compact to large extended sources, the default value of 5σ was appropriate
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