RT9CC15GHZ - 9C Continued 15-GHz Ryle Telescope Survey of VSA Fields Source Catalog

Overview

The 9C (9th Cambridge) survey of radio sources with the Ryle Telescope at 15.2 GHz was set up to survey the fields of the cosmic microwave background telescope, the Very Small Array (VSA). In their first paper (Waldram et al. 2003, MNRAS, 342, 915), the authors described three regions of the survey, constituting a total area of 529 deg² to a completeness limit of ~ 25 mJy. In this follow-up, they present results from a series of deeper regions, constituting a total area of 115 deg² complete to ~ 10 mJy and of 29 deg² complete to ~ 5.5 mJy. The authors have investigated the source counts and the distributions of the 1.4 to 15.2 GHz spectral indices for these deeper samples. The whole catalog of 643 sources is contained in the present table.

Down to their lower limit of 5.5 mJy, the authors detect no evidence for any change in the differential source count from the earlier fitted count above 25 mJy, n(S) = 51(S/Jy)^-2.15 Jy^-1 sr^-1. They matched both their new and earlier catalogues with the NRAO VLA Sky Survey (NVSS) catalogue at 1.4 GHz and selected flux-limited samples at both 15 and 1.4 GHz. As they expected, they found that the proportions of sources with flat and rising spectra in the samples selected at 15 GHz are significantly higher than those in the samples selected at 1.4 GHz. In addition, for 15-GHz samples selected in three flux density ranges, they detect a significant shift in the median value of the 1.4 to 15.2 GHz spectral index: the higher the flux densities, the higher the proportions of sources with flat and rising spectra.

In the area complete to ~ 10 mJy, the authors find five sources between 10 and 15 mJy at 15 GHz, amounting to 4.3 per cent of sources in this range, with no counterpart in the NVSS catalogue. This implies that, had they relied on the NVSS for locating their sources, they could have missed a significant proportion of them at low flux densities.

These results illustrate the problems inherent in using a low-frequency catalog to characterize the source population at a much higher frequency and emphasize the value of a blind 15.2-GHz survey.

Catalog Bibcode

2010MNRAS.404.1005W

References

9C continued: results from a deeper radio-source survey at 15GHz.
    Waldram E.M., Pooley G.G., Davies M.L., Grainge K.J.B., Scott P.F.
   <Mon. Not. R. Astron. Soc., 404, 1005-1017 (2010)>
   =2010MNRAS.404.1005W
9C: a survey of radio sources at 15 GHz with the Ryle Telescope. [Paper I]
    Waldram E.M., Pooley G.G., Grainge K.J.B., Jones M.E., Saunders R.D.E.,
    Scott P.F., Taylor A.C.
   <Mon. Not. R. Astron. Soc. 342, 915 (2003)>
   =2003MNRAS.342..915W

Provenance

This table was created in November 2010 based on CDS catalog J/MNRAS/404/1005 file 9c_cont.dat.

Parameters

Name
The position-based source designation adopted by the HEASARC, viz., '9C JHHMM+DDMMa', where the numerical part of the name is the truncated J2000.0 position of the radio source. Where there are two apparently independent sources which would otherwise have the same abbreviated source name, the authors added an a 'a' or 'b' to the name. The CDS Dictionary of Nomenclature of Celestial Objects currently recommends a truncated version of this naming convention, viz., '9C JHHMM+DDMM'.

RA
The Right Ascension of the 15.2-GHz radio source in the selected equinox. This was given in J2000.0 equatorial coordinates in the original table to a precision of 0.1 seconds of time. The position of a source was derived from a raster map, unless the follow-up pointed observation indicated a position differing by more than 10 arcseconds, in which case the latter position is substituted. However, since there were large overlaps between adjacent raster maps and a number of sources appeared on more than one map, it was possible to make a general estimate of the position accuracy. Taking the 0020+2947 field, the authors found 39 sources with repeat position measurements. Apart from one extended source, in no case did the measurements differ by more than 10 arcseconds and the median difference was ~ 4 arcseconds.

Dec
The Declination of the 15.2-GHz radio source in the selected equinox. This was given in J2000.0 equatorial coordinates in the original table to a precision of 1 arcsecond. The position of a source was derived from a raster map, unless the follow-up pointed observation indicated a position differing by more than 10 arcseconds, in which case the latter position is substituted. However, since there were large overlaps between adjacent raster maps and a number of sources appeared on more than one map, it was possible to make a general estimate of the position accuracy. Taking the 0020+2947 field, the authors found 39 sources with flux densities in the range of 4.6 to 68.3 mJy which had repeat position measurements. Apart from one extended source, in no case did the measurements differ by more than 10 arcseconds and the median difference was ~ 4 arcseconds. For brighter sources, the positions are espected to be accurate to <~ 3 arcseconds based on findings from Paper I.

LII
The Galactic Longitude of the 15.2-GHz radio source.

BII
The Galactic Latitude of the 15.2-GHz radio source.

Flux_2_cm
The 15.2-GHz flux density of the source, in either mJy/beam (for the peak value of point sources) or mJy (for the integrated value for extended sources), as derived from the follow-up pointed observation. (These values were converted by the HEASARC from the Jy/beam and Jy units used in the original table).The uncertainty in the flux densities is dominated by the uncertainty in the flux calibration, which is ~ 5 per cent

Date_Observed
The date of the pointed observation of the source. This information is included because a number of the sources are highly variable.

Deep_Flag
This flag parameter is set to 'D' to indicate that the source was detected in one of the deeper survey regions complete to ~ 5.5 mJy; otherwise, for regions in the overall survey complete to ~ 10 mJy. it is left blank.

Source_Flag
This flag parameter is set to indicate either binary and/or extended source morphology, as follows:

       b  = indicates binary source
       e  = extended source
       e? = possibly extended source

Contact Person

Questions regarding the RT9CC15GHZ database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: Tuesday, 02-Nov-2010 10:40:26 EDT