GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey – I. A low-frequency extragalactic catalogue

Abstract

Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalogue, utilising the first year of observations. The catalogue covers 24, 831 square degrees, over declinations south of +30 • and Galactic latitudes outside 10 • of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307,455 radio sources with 20 separate flux density measurements across 72-231 MHz, selected from a time-and frequency-integrated image centred at 200 MHz, with a resolution of ≈ 2 . Over the catalogued region, we estimate that the catalogue is 90 % complete at 170 mJy, and 50 % complete at 55 mJy, and large areas are complete at even lower flux density levels. Its reliability is 99.97 % above the detection threshold of 5σ, which itself is typically 50 mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low frequency flux density scale of the southern sky to better than 10 %. This paper presents details of the flagging, imaging, mosaicking, and source extraction/characterisation, as well as estimates of the completeness and reliability. All source measurements and images are available online . This is the first in a series of publications describing the GLEAM survey results.

Calibration of Ultraviolet, Mid-infrared, and Radio Star Formation Rate Indicators

“…The TGSS ADR1 is optimized for imaging of compact sources, and therefore becomes less reliable for measuring flux densities for galaxies larger than a few arcminutes. For the brightest radio sources in our sample, we used flux densities from the Sixth and Seventh Cambridge Surveys of Radio Sources (6C and 7C; Baldwin et al 1985;Hales et al 1988Hales et al , 1990Hales et al , 1991Hales et al , 1993aHales et al , 1993bHales et al , 2007 and the GaLactic and Extragalactic All-Sky MWA Survey (GLEAM; Wayth et al 2015;Hurley-Walker et al 2017), which do not have the angular size limitations of the TGSS but are more prone to source confusion. Changes to the selection criteria used for radio flux density measurements (e.g., the criteria used to exclude large galaxies) had little impact on our SFR indicator calibrations.…”

“…a 150 MHz flux density from 6C or 7C (Baldwin et al 1985;Hales et al 1988Hales et al , 1990Hales et al , 1991Hales et al , 1993aHales et al , 1993bHales et al , 2007. b 150 MHz flux density from GLEAM (Wayth et al 2015;Hurley-Walker et al 2017).…”

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

“…27 The two projects utilize two different observing strategies; GLEAM Hurley-Walker et al 2016) uses a drift-scan observing mode, i.e., the tiles always point to the meridian, whereas the EoR observations track the field over ∼4 hr with quantized beamformer settings that are separated by about 7° ( Paul et al 2014;Trott 2014;Jacobs et al 2016). The EoR observations enable deep scans of individual fields, whereas the GLEAM observations minimize instrumental systematics by maintaining a consistent observing set up.…”

Connecting X-ray absorption and 21 cm neutral hydrogen absorption in obscured radio AGN

“…The GaLactic and Extragalactic All-sky MWA survey (GLEAM, Wayth et al 2015;Hurley-Walker et al 2017) observed the entire sky south of +30 • declination at twenty different frequencies between 72 and 231 MHz. The extragalactic catalogue formed from the GLEAM survey consists of 307,455 sources, with positions accurate to ∼ 30 .…”