GMRTHA325M - Giant Metrewave Radio Telescope Herschel-ATLAS/GAMA Flds 325-MHz Source Catalog

Overview

This table contains a source list from a 325-MHz survey undertaken with the Giant Metrewave Radio Telescope (GMRT). This survey covers a large part of the three equatorial fields at 9, 12 and 14.5 h of Right Ascension from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) in the area also covered by the Galaxy And Mass Assembly (GAMA) survey. The full data set, after some observed pointings were removed during the data reduction process, comprises 212 GMRT pointings covering ~90 deg² of sky. A list of the central coordinates of the images from which the sources listed in this catalog are derived is available at http://gmrt-gama.extragalactic.info/GMRT_GAMA_IMAGE_CENTERS. The images themselves are available at http://gmrt-gama.extragalactic.info/.

The authors have imaged and catalogued the data using a pipeline that automates the process of flagging, calibration, self-calibration and source detection for each of the survey pointings. The resulting images have resolutions of between 14 and 24 arcseconds and minimum rms noise (away from bright sources) of ~1 mJy beam^-1, and the catalogue contains 5263 sources brighter than the local 5 sigma values. In the reference paper, the authors investigate the spectral indices of those GMRT sources which are also detected at 1.4 GHz and find them to agree broadly with previously published results; there is no evidence for any flattening of the radio spectral index below S_1.4 = 10 mJy. This work adds to the large amount of available optical and infrared data in the H-ATLAS equatorial fields and will facilitate further study of the low-frequency radio properties of star formation and AGN activity in galaxies out to z ~1.

Catalog Bibcode

2013MNRAS.435..650M

References

A 325-MHz GMRT survey of the Herschel-ATLAS/GAMA fields
    Mauch T., Kloeckner H.-R., Rawlings S., Jarvis M., Hardcastle M. J.,
    Obreschkow D., Saikia D. J., Thompson M. A.
   <Mon. Not. R. Astron. Soc., 435, 650-662 (2013)>
   =2013MNRAS.435..650M

Provenance

This table was created by the HEASARC in December 2013 based on electronic versions of the 3 catalogs that comprise Table 3 from the reference paper which were obtained from the MNRAS web site. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018.

Parameters

Field_Name
This survey covered 3 spatially distinct H-ATLAS/GAMA fields and the table herein contains the sources detected in these 3 fields. To allow users to more easily filter on these fields, the HEASARC created the field_name parameter which is set to '9h', '12h', or to '14.5h' for sources in the H-ATLAS fields at 9, 12 or 14.5 hours RA, respectively.

Name
The 325-MHz source designation. This parameter was created by the HEASARC following the CDS Dictionary of Nomenclature of Celestial Objects recommendations for J2000.0 position-based source names, e.g., '[MKR2013] J083523.4+000154', where MKR2013 refers to the Mauch, Kloeckner, Rawlings 2013 reference paper.

RA
The Right Ascension of the radio source in the selected equinox. This was given in J2000.0 coordinates to a precision of 10^-5 degrees in the original table.

RA_Error
The error in the quoted Right Ascension, in arcseconds. This is calculated from the quadratic sum of the calibration uncertainty, described in Section 5.3 of the reference paper, and the fitting uncertainty, calculated using the equations given by Condon (1997, PASP, 109, 166).

Dec
The Declination of the radio source in the selected equinox. This was given in J2000.0 coordinates to a precision of 10^-5 degrees in the original table.

Dec_Error
The error in the quoted Declination, in arcseconds. This is calculated from the quadratic sum of the calibration uncertainty, described in Section 5.3 of the reference paper, and the fitting uncertainty, calculated using the equations given by Condon (1997, PASP, 109, 166).

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Flux_325_MHz
The fitted 325-MHz peak brightness of the radio source, in units of mJy beam^-1. The raw brightness measured from the image has been increased by 0.9 mJy beam^-1 to account for the effects of clean bias (see Section 5.2 of the reference paper).

Flux_325_MHz_Error
The uncertainty in the fitted 325-MHz peak brightness of the radio source, in units of mJy beam^-1, calculated from the quadratic sum of the fitting uncertainty from the equations given by Condon (1997, PASP, 109, 166) and the estimated 5 per cent flux calibration uncertainty of the GMRT.

Int_Flux_325_MHz
The total (integrated) 325-MHz flux density of the source, in mJy. This equals the fitted peak brightness if the source is unresolved.

Int_Flux_325_MHz_Error
The uncertainty in the total (integrated) 325-MHz flux density of the source, in mJy, calculated from equations given by Condon (1997, PASP, 109, 166).

Major_Axis
The major axis FWHM, in arcseconds, of the fitted elliptical Gaussian to the radio source. As discussed in Section 5.4 of the reference paper, the fitted sizes are only quoted for sources that are moderately resolved in their minor axes.

Major_Axis_Error
The uncertainty in the fitted major axis FWHM of the elliptical Gaussian, in arcseconds. This is calculated using equations taken from Condon (1997, PASP, 109, 166).

Minor_Axis
The minor axis FWHM, in arcseconds, of the fitted elliptical Gaussian to the radio source. As discussed in Section 5.4 of the reference paper, the fitted sizes are only quoted for sources that are moderately resolved in their minor axes.

Minor_Axis_Error
The uncertainty in the fitted minor axis FWHM of the elliptical Gaussian, in arcseconds. This is calculated using equations taken from Condon (1997, PASP, 109, 166).

Position_Angle
The position angle (PA) of the fitted elliptical Gaussian to the radio source, in degrees. As discussed in Section 5.4 of the reference paper, the fitted sizes are only quoted for sources that are moderately resolved in their minor axes. The PA is only meaningful for sources that are resolved, i.e. when the fitted Gaussian is larger than the restoring beam for the relevant field (14 arcseconds for the 9-h field, 15 arcseconds for the 12-h field and 23.5 arcseconds for the 14.5-h field).

Position_Angle_Error
The uncertainty in the position angle (PA) of the fitted elliptical Gaussian to the radio source, in degrees. This is calculated using equations taken from Condon (1997, PASP, 109, 166).

RMS_325_MHz
The local rms noise (sigma_local), in mJy beam^-1, at the source position, calculated as described in Section 3.3 of the reference paper. The local rms is used to determine the source signal-to-noise ratio, the latter being used to determine the fitting uncertainties.

Image_Name
The name of the GMRT mosaicked image containing the source. These names consist of the letters PN, a letter A, B or C indicating the 9-, 12- or 14.5-h fields, respectively, and a number between 01 and 96 which gives the pointing number within that field (see Fig. 1 of the reference paper for a diagram showing the 9-h field). These images are available at http://gmrt-gama.extragalactic.info/.

Contact Person

Questions regarding the GMRTHA325M database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:28:13 EDT