MWA32THGL - Murchison Widefield Array 32-T Low-Frequency Source Catalog

Overview

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 deg², 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^h 18^m 6^s, Dec (J2000) = -12^o 5' 45" to facilitate calibration. The other covered the Epoch of Reionization (EoR) field 2, centered at RA (J2000) = 10^h 20^m 0^s, Dec (J2000) = -10^o 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.

Catalog Bibcode

2012ApJ...755...47W

References

Low Frequency Imaging of Fields at High Galactic Latitude with the
Murchison Widefield Array 32-Element Prototype
         Williams C.L., Hewitt J.N., Levine A.M., de Oliveira-Costa A.,
         Bowman J.D., Briggs F.H., Gaensler B.M., Hernquist L.L., Mitchell
         D.A., Morales M.F., Sethi S.K., Subrahmanyan R., Sadler E.M.,
         Arcus W., Barnes D.G., Bernardi G., Bunton J.D., Cappallo R.C.,
         Crosse B.W., Corey B.E., Deshpande A., deSouza L., Emrich D.,
         Goeke R.F., Greenhill L.J., Hazelton B.J., Herne D., Kaplan D.L.,
         Kasper J.C., Kincaid B.B., Koenig R., Kratzenberg E., Lonsdale
         C.J., Lynch M.J., McWhirter S.R., Morgan E.H., Oberoi D., Ord
         S.M., Pathikulangara J., Prabu T., Remillard R.A., Rogers A.E.E.,
         Roshi D.A., Salah J.E., Sault R.J., Shankar N.U., Srivani K.S.,
         Stevens J.B., Tingay S.J., Wayth R.B., Waterson M., Webster R.L.,
         Whitney A.R., Williams A.J., Wyithe J.S.B.
        <Astrophys. J., 755, 47. (2012)>
        =2012ApJ...755...47W

Provenance

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.

Parameters

Name
The MWA-32T source designation, using the prefix '[WHL2012] MWA' for William, Hewitt, Levine 2012 Murchison Widefield Array and the J2000.0 equatorial position of the source, e.g., '[WHL2012] MWA J0747-1854'. The HEASARC constructed these names in conformance with the guidelines of the Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 0.01 degrees in the original table.

Dec
The Declination of the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 0.01 degrees in the original table.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Average_Flux
The flux density of the radio source in the full-band (108.16 to 200.32 MHz) average map, in mJy (converted by the HEASARC from the Jy units given in the original table). For each field, 30.72-MHz bandwidth maps centered at 123.52 MHz, 154.24 MHz, and 184.96 MHz were made from four 7.68 MHz maps. Before averaging, the 7.68 MHz map fluxes were scaled to the averaged map frequency using an assumed spectral index alpha of -0.8 (where S ~ nu^alpha). A full-band (92.16-MHz bandwidth) weighted average map was made from the three 30.72-MHz bandwidth maps after scaling them to a common reference frequency of 154.24 MHz, again using a spectral index of -0.8.

Average_Flux_Error
The uncertainty in the average map flux density of the radio source, in mJy (converted by the HEASARC from the Jy units given in the original table).

Flux_124_MHz
The flux density of the radio source in the 30.72-MHz wide sub-band centered at 123.52 MHz, in mJy (converted by the HEASARC from the Jy units given in the original table).

Flux_124_MHz_Error
The uncertainty in the flux density of the radio source in the 123.52-MHz sub-band, in mJy (converted by the HEASARC from the Jy units given in the original table).

Flux_154_MHz
The flux density of the radio source in the 30.72-MHz wide sub-band centered at 154.24 MHz, in mJy (converted by the HEASARC from the Jy units given in the original table).

Flux_154_MHz_Error
The uncertainty in the flux density of the radio source in the 154.24-MHz sub-band, in mJy (converted by the HEASARC from the Jy units given in the original table).

Flux_185_MHz
The flux density of the radio source in the 30.72-MHz wide sub-band centered at 184.96 MHz, in mJy (converted by the HEASARC from the Jy units given in the original table).

Flux_185_MHz_Error
The uncertainty in the flux density of the radio source in the 184.96-MHz sub-band, in mJy (converted by the HEASARC from the Jy units given in the original table).

Field_ID
The field from which the radio source measurement was taken: 'HydA' for the Hydra A field or 'EOR2' for the Epoch of Reionization (EoR) field 2, See the Overview above for more details.

Off_Axis
The angular distance, in degrees, of the radio source from the center of the field from which the measurement was taken.

Detection_SNR
The signal-to-noise ratio at which the source was detected in the full-band-averaged map.

Contact Person

Questions regarding the MWA32THGL database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:31:17 EDT