Description
The Murchison Widefield Array (MWA) is a new low-frequency, wide-field-of-view radio interferometer under development at the Murchison Radio-astronomy Observatory in Western Australia. The authors have used a 32 element MWA prototype interferometer (MWA-32T) to observe two 50 degree diameter fields in the southern sky, covering a total of ~ 2700 deg<sup>2</sup>, in order to evaluate the performance of the MWA-32T, to develop techniques for epoch of reionization experiments, and to make measurements of astronomical foregrounds. They developed a calibration and imaging pipeline for the MWA-32T, and used it to produce ~15 arcminutes angular resolution maps of the two fields in the 110-200 MHz band. The authors perform a blind source extraction using these confusion-limited images, and detect 655 sources at high significance with an additional 871 lower significance source candidates. They compare these sources with existing low-frequency radio surveys in their paper in order to assess the MWA-32T system performance, wide-field analysis algorithms, and catalog quality. Their source catalog is found to agree well with existing low-frequency surveys in these regions of the sky and with statistical distributions of point sources derived from Northern Hemisphere surveys; it represents one of the deepest surveys to date of this sky field in the 110-200 MHz band. Observations were conducted with the MWA-32T in 2010 March during a two-week campaign (X13). Data were taken in three 30.72 MHz sub-bands centered at 123.52 MHz, 154.24 MHz, and 184.96 MHz in order to give (nearly) continuous frequency coverage between ~ 110 MHz and ~ 200 MHz. The observing time was divided between two fields. One field was centered on the bright extragalactic source Hydra A at RA (J2000) = 9<sup>h</sup> 18<sup>m</sup> 6<sup>s</sup>, Dec (J2000) = -12^o 5' 45" to facilitate calibration. The other covered the Epoch of Reionization (EoR) field 2, centered at RA (J2000) = 10<sup>h</sup> 20<sup>m</sup> 0<sup>s</sup>, Dec (J2000) = -10<sup>o</sup> 0' 0". The EoR2 field is one of two fields at high Galactic latitude that have been identified by the MWA Collaboration as targets for future EoR experiments. Although the centers of the Hydra A and EoR2 fields are separated by 15.3 degrees, there is considerable overlap between them since the half-power beam width of the primary beam is ~ 25 degrees at 150 MHz. Table 1 in the reference paper gives a journal of the observations. This table contains 648 radio sources which were detected in the full-band average map at or above a signal-to-noise ratio of 5. This table was created by the HEASARC in October 2012, based on an electronic version of table 2 from the reference paper as obtained from the ApJ website. This is a service provided by NASA HEASARC .
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