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GMRTJ0916 - Giant Metrewave Radio Telescope J0916+6348 Field Radio Source Catalog

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Overview

This table contains a catalog based on deep multifrequency observations made using the Giant Metrewave Radio Telescope (GMRT) at 153, 244, 610 and 1260 MHz of a field centred on J0916+6348, to search for evidence of fossil radio lobes which could be due to an earlier cycle of episodic activity of the parent galaxy, as well as haloes and relics in clusters of galaxies. The authors do not find any unambiguous evidence of episodic activity in a list of 374 sources, suggesting that such activity is rare even in relatively deep low-frequency observations. The authors examine the spectra of all the sources by combining their observations with those from the Westerbork Northern Sky Survey (WENSS), NRAO (National Radio Astronomy Observatories) VLA (Very Large Array) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty-Centimeters Survey (FIRST). Considering only those which have measurements at a minimum of 3 different frequencies, they find that almost all sources are consistent with a straight spectrum with a median spectral index alpha ~ 0.8 (Snu ~ nu-alpha) which appears steeper than theoretical expectations of the injection spectral index. The authors identify 14 very-steep-spectrum sources with alpha >~ 1.3.

This table contains the list of 317 sources (out of the 374 sources which were within 1.5 degrees of the phase center at 153 MHz and had peak brightnesses at least 6 times larger than the local rms value) which were detected at a minimum of 3 frequencies out of the 6 frequencies (153, 244, 327, 610, 1260 and 1400 MHz) which were utilized in this study.

The new observations were made on 2005 December 12 at 153 MHz, 2005 November 26 at 244 MHz and 610 MHz, and on 2008 April 22 at 1260 MHz, on the Giant Metrewave Radio Telescope (Pune, India).


Catalog Bibcode

2009MNRAS.392.1403S

References

Deep low-frequency observations with the Giant Metrewave Radio Telescope:
a search for relic radio emission.
    Sirothia S.K., Saikia D.J., Ishwara-Chandra C.H., Kantharia N.G.
   <Mon. Not. R. Astron. Soc., 392, 1403-1412 (2009)>
   =2009MNRAS.392.1403S

Provenance

This table was created by the HEASARC in March 2012 based on CDS Catalog J/MNRAS/392/1403 file table2.dat.

Parameters

Name
The name of the radio source constructed by the HEASARC using the IAU-style designation for the source based on its truncated J2000.0 equatorial coordinates, viz., '[SSI2009] JHHMMSS+DDMMSS', as recommended by the CDS Dictionary of Nomenclature of Celestial Objects, where the '[SSI2009]' prefix stands for 'Sirothia, Saikia, Ishwara-Chandra 2009'.

RA
The Right Ascension of the radio source in the selected equinox, estimated from the flux-density weighted centroid of all the emission enclosed by the 3-sigma contour at 153 MHz. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the radio source in the selected equinox, estimated from the flux-density weighted centroid of all the emission enclosed by the 3-sigma contour at 153 MHz. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Off_Axis
The distance from the GMRT pointing center to the centroid of the radio source in the 153-MHz image, in arcminutes.

Flux_153_MHz
The total flux density of the radio source at 153 MHz, in mJy, estimated by integrating the emission within the 3-sigma closed contour. The authors estimate the errors in the 153-MHz flux densities to be ~ 15%.

Flux_244_MHz
The total flux density of the radio source at 244 MHz, in mJy, estimated by integrating the emission within the 3-sigma closed contour. The authors estimate the errors in the 244-MHz flux densities to be ~ 15%.

WENSS_Flux_330_MHz
The total flux density of the radio source at 330 MHz, in mJy, taken from the WENSS Catalog.

Flux_610_MHz
The total flux density of the radio source at 610 MHz, in mJy, estimated by integrating the emission within the 3-sigma closed contour. The authors estimate the errors in the 610-MHz flux densities to be ~ 10%. This is listed only for those sources which are within 0.54 degrees (32.4 arcminutes) of the phase center, which corresponds to about 20% of the peak response of the primary beam. The flux densities of a few sources which are extended at 610 MHz have not been listed if significant flux density appeared to be missing in the image even after convolving it to a lower resolution.

Flux_1260_MHz
The total flux density of the radio source at 1260 MHz, in mJy, estimated by integrating the emission within the 3-sigma closed contour. The authors estimate the errors in the 1260-MHz flux densities to be ~ 5%. This is listed only for those sources which are within 0.34 degrees (20.4 arcminutes) of the phase center, which corresponds to about 20% of the peak response of the primary beam. The flux densities of a few sources which are extended at 1260 MHz have not been listed if significant flux density appeared to be missing in the image even after convolving it to a lower resolution.

NVSS_Flux_1400_MHz
The total flux density of the radio source at 1400 MHz, in mJy, taken from the NVSS Catalog.

Spectral_Index
The spectral index of the radio source from a linear least-squares fit for which the spectrum could be satisfactorily fitted with a single power-law spectrum. For sources which showed a strong departure from such a fit, a parabolic form log Snu = b*(log nu)2 + m*(log nu) + c was fitted and the high-frequency spectral indices between 610 and 1400 MHz have been quoted. The authors estimate that the error in the value of the spectral index is typically ~ 0.15.

Source_Type
The radio source structural classification, usually done from the highest resoloution image available, usually the GMRT image at either 610 or 1260 MHz or the FIRST image at 1400 MHz, and coded as follows:

        D = double-lobed source
        E = diffuse extended emission without a clear double-lobed structure
        S = single source
        T = triple source with a possible core component
     Cplx = complex source
  

Contact Person

Questions regarding the GMRTJ0916 database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 5-Mar-2012