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LD7C151MHZ - 7C 151-MHz Low-Declination Survey Catalog

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Overview

The Cambridge Low Frequency Synthesis Telescope (CLFST) has been used at 151 MHz to survey a region of 1393 square degrees, in the range of RA from 9h to 16h, and of Dec from 20o to 35o, with an angular resolution of 108 x 108cosec(Dec) arcsec2. The rms noise in the maps is in general ~ 35 - 55 mJy/beam, but varies considerably and exceeds this in some areas. The authors have extracted sources with signal-to-noise ratio > 5.5, a total of 5526 sources, and this table contains the catalog of their positions and flux densities.

Catalog Bibcode

1996MNRAS.282..779W

References

The 7C Survey of Radio Sources at 151 MHz - a region covering
RA 9h to 16h and Dec 20 deg to 35 deg.
      Waldram E.M., Yates J.A., Riley J.M., Warner P.J.
     <Mon. Not. R. Astron. Soc. 282, 779 (1996)>
     =1996MNRAS.282..779W

Provenance

This table was created by the HEASARC in October 2010 based on CDS table J/MNRAS/282/779 file 7c_low.dat.

Parameters

Name
The source designation adopted by the HEASARC, viz., '7C HHMMSS.s+DDMMSS', where the numerical part of the name is the B1950.0 beam-fitted position of the radio source. Sometimes, a truncated version of this naming convention, viz., '7C HHMM+DDMMa' has been used, but the HEASARC has adopted the higher precision position-based naming convention that is now recommended for the primary 7C catalog.

RA
The Right Ascension of the beam-fitted position of the radio source in the selected equinox. This was given in B1950.0 equatorial coordinates in the original table to a precision of 0.1 seconds of time. The rms (1-sigma) accuracy of the beam-fitted RA is approximately sqrt[22 + (40/SNR)2] arcseconds, where the 2 arseconds part is the error introduced by random phase errors, and the (40/SNR) part is the error due to source confusion and noise.

Dec
The Declination of the beam-fitted position of the radio source in the selected equinox. This was given in B1950.0 equatorial coordinates in the original table to a precision of 1 arcsecond. The rms (1-sigma) accuracy of the beam-fitted Dec is approximately 1.3 cosec(Dec) times the rms error in RA: the dependence on Declination increases more rapidly than the expected factor of cosec(Dec) because of the effects of the distortion of the beam shape and confusion.

LII
The Galactic Longitude of the beam-fitted position of the radio source.

BII
The Galactic Latitude of the beam-fitted position of the radio source

Centroid_RA
The Right Ascension of the centroid position of the radio source in the selected equinox. This was given in B1950.0 equatorial coordinates in the original table to a precision of 0.1 seconds of time. Multiple peaks which have been integrated together have the same centroid position.

Centroid_Dec
The Declination of the centroid position of the radio source in the selected equinox. This was given in B1950.0 equatorial coordinates in the original table to a precision of 1 arcsecond. Multiple peaks which have been integrated together have the same centroid position.

Flux_151_MHz
The beam-fitted flux density Sbf of the radio source at 151 MHz, in mJy/beam (converted by the HEASARC from the Jy/beam units used in the original table). Monte Carlo analysis showed that, in the absence of phase errors, the fractional errors in Sbf are given by the inverse of the signal-to-noise ratio, 1/SNR. The effects of random phase errors limit the accuracy fo high-SNR (>= 40) sources to 2-3 percent.

Int_Flux_151_MHz
The integrated flux density Sin of the radio source at 151 MHz, in mJy (converted by the HEASARC from the Jy units used in the original table). The errors in Sin are a factor of ~ 1.5 times larger than those of the beam-fitted flux values; this factor increases to ~ 3 for the lowest Declinations mainly because of the effects of confusion. A conservative estimate of the integrated flux density errors for the sources with SNR > 15 is around 10 per cent.

SNR
The signal-to-noise ratio SNR of the radio source as defined by Waldram and Riley (1993, MNRAS, 265, 853), i.e., the interpolated peak height of the source on the map (after subtraction of the local zero level), divided by the local noise. The minimum SNR value for sources in this table is 5.5.

Source_Extent
The extent of the source size in units of the local beam area. This estimate is influenced by residual ionospheric smearing of the synthesized beam. Another measure of whether a source is resolved or not is the ratio of the integrated to beam-fitted flux densities, Sin/Sbf. The flux density calibration is performed in such a way as to ensure that the median value of this ratio for unresolved sources is unity. Thus, any source with this ratio >> 1 is resolved, and, for this survey, a ratio of Sin/Sbf >= 1.3 is a more robust indication that the source is resolved.

Num_Local_Max
The number m of individual peaks that were included in the flux integration. For multiple sources, each peak has a separate entry in this source list, with its own beam-fitted flux density and position, although the integrated flux, the centroid position, the source extent and m are the same for each such entry.


Contact Person

Questions regarding the LD7C151MHZ database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 28-Aug-2012