Abstract
AbstractThe low-frequency linearly polarised radio source population is largely unexplored. However, a renaissance in low-frequency polarimetry has been enabled by pathfinder and precursor instruments for the Square Kilometre Array. In this second paper from the POlarised GaLactic and Extragalactic All-Sky MWA Survey-the POlarised GLEAM Survey, or POGS-we present the results from our all-sky MWA Phase I Faraday Rotation Measure survey. Our survey covers nearly the entire Southern sky in the Declination range$-82^\circ$to$+30^\circ$at a resolution between around three and seven arcminutes (depending on Declination) using data in the frequency range 169−231 MHz. We have performed two targeted searches: the first covering 25 489 square degrees of sky, searching for extragalactic polarised sources; the second covering the entire sky South of Declination$+30^\circ$, searching for known pulsars. We detect a total of 517 sources with 200 MHz linearly polarised flux densities between 9.9 mJy and 1.7 Jy, of which 33 are known radio pulsars. All sources in our catalogues have Faraday rotation measures in the range$-328.07$to$+279.62$rad m−2. The Faraday rotation measures are broadly consistent with results from higher-frequency surveys, but with typically more than an order of magnitude improvement in the precision, highlighting the power of low-frequency polarisation surveys to accurately study Galactic and extragalactic magnetic fields. We discuss the properties of our extragalactic and known-pulsar source population, how the sky distribution relates to Galactic features, and identify a handful of new pulsar candidates among our nominally extragalactic source population.
Highlights
The construction of an all-sky grid of polarised sources with which to probe the large-scale magnetised Universe is one of the high-priority goals of many surveys with next-generation radio telescopes
In this second paper from the POlarised GaLactic and Extragalactic All-Sky MWA Survey-the POlarised GaLactic and Extragalactic All-sky MWA survey (GLEAM) Survey, or POGS-we present the results from our all-sky MWA Phase I Faraday Rotation Measure survey
We have presented the all-sky results from the POlarised GLEAM Survey (POGS)
Summary
The construction of an all-sky grid of polarised sources with which to probe the large-scale magnetised Universe is one of the high-priority goals of many surveys with next-generation radio telescopes. The POlarisation Sky Survey of the Universe’s Magnetism (POSSUM; Gaensler et al 2010) project with the Australian Square Kilometre Array Pathfinder (ASKAP; Johnston et al 2007) is predicted to detect up to million polarised sources across the Southern sky (South of Declination around +30◦) Such all-sky grids can be used as statistical probes of cosmic magnetism, and a number of large-N studies have already been performed using previous state-of-the-art polarisation catalogues to probe both the Galactic magnetised foreground (e.g., Oppermann et al 2012, 2015; Hutschenreuter & Enßlin 2020) and the extragalactic magnetised Universe (e.g., Vernstrom et al 2019). In recent years, the low-frequency polarised sky has been explored in greater detail than ever before, with detections of large-scale diffuse Galactic foreground along many lines of sight (LOSs) (e.g., Jelicet al. 2015; Lenc et al 2016; Van Eck et al 2017, 2019) as well as many surveys that have begun to study the polarised extragalactic source population (e.g., Bernardi et al 2013; Mulcahy et al 2014; Van Eck et al 2017; Lenc et al 2018; Neld et al 2018; O’Sullivan et al 2019, 2020; Stuardi et al 2020; Cantwell et al 2020)
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