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Description
Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, the authors have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalog, utilizing the first year of observations. The catalog covers 24,402 square degrees, over Declinations south of +30 degrees and Galactic latitudes outside 10 degrees 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 centered at 200 MHz, with a resolution of ~ 2 arcminutes. Over the catalogued region, the authors estimate that the catalog 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 5-sigma detection threshold, 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%. The reference paper presents details of the flagging, imaging, mosaicking, and source extraction/characterization, as well as estimates of the completeness and reliability. All source measurements and images are available online at <a href="http://www.mwatelescope.org/">http://www.mwatelescope.org/</a>. This is the first in a series of publications describing the GLEAM survey results. GLEAM observes in week-long drift scan campaigns, with a single Dec strip observed each night. The observing bandwidth of 72-231 MHz is covered by shifting frequencies by 30.72 MHz every two minutes, avoiding the Orbcomm satellite constellation at 134-139 MHz. Thus, the frequencies of observation are 72-103, 103-134, 139-170, 170-200. and 200-231 MHz. These may be further subdivided for imaging purposes; in this study, the 30.72 MHz bandwidth is commonly subdivided into four 7.68 MHz sub-channels. The native channel resolution of these observations is 40 kHz and the native time resolution is 0.5 seconds. This paper concerns only data collected in the first year, i.e. four weeks between June 2013 and July 2014. The authors also do not image every observation, since the survey is redundant across approximately 50% of the observed RA ranges, and some parts are adversely acted by the Galactic plane and Centaurus A. Table 1 in the reference paper lists the observations which have been used to create this first GLEAM catalog. The HEASARC has converted the flux density units from those given in the original table (Jy and Jy/beam) to its standard units for radio flux densities (mJy and mJy/beam). This table was originally ingest by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/VIII/100">CDS Catalog VIII/100</a> file gleamegc.dat, the GLEAM Extragalactic Catalog. It was updated in May 2018 to the corrected version provided to the CDS by the author. This is a service provided by NASA HEASARC .
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