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UC7C151MHZ - 7C Catalog 151-MHz Survey Final Unified Source Catalog

HEASARC
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Overview

This table contains a final unified catalog for the 7C survey at 151 MHz with a spatial resolution of 70 x 70cosec(Dec) arcsec2. This has been constructed by amalgamating the existing catalogs derived from individual fields imaged at this resolution and eliminating redundancy in regions of mutual overlap. This was a non-trivial procedure because the flux in multiple-component sources may be fitted differently on alternative images, owing, for example, to differences in local noise and beam distortion. The final catalog as published thus produced contains 43683 sources. (Note that the HEASARC removed one duplicate source entry for '7C 083231.6+262635' since it had two entries, which were identical except that in one the beam-fitted flux density Sbf was 834 mJy/beam, while, in the other entry now removed, Sbf was 840 mJy/beam). Separate final catalogs have been previously published for the 7C Galactic Plane 7CG survey (available as the HEASARC table GP7C151MHZ), and the lower-resolution survey of the low-declination strip 9h < RA < 16h, 20o < Dec < 35o (available as the HEASARC table LD7C151MHZ).

The individual catalogs for about 40 of the 96 regions contributing to the total have already been published, together with full details of the methodology, in MNRAS or A&AS:

    Reference                              Region

    Lacy et al. 1995, MNRAS, 276, 614       92
    Visser et al. 1995, A&AS, 110, 419      93
    Pooley et al. 1998, MNRAS, 298, 637     94-96
    Riley et al. 1999, MNRAS, 306, 31        1-33
and these data are also available via the MRAO website: http://www.mrao.cam.ac.uk/surveys/7C/

Individual catalogs for the remaining 58 regions by Riley et al. (regions 34-91) were released electronically via the MRAO website in November 2001. These include a re-analysis of data originally published in rather a different parametrization by McGilchrist et al. 1990, MNRAS, 246, 110. The regions re-analyzed are those numbered 41, 44, 59, 60, 62 and 63 and they supersede McGilchrist's 1990 publication.

The RA x Dec coverage, the average rms noise, the flux density of the faintest source listed and the completeness limit for each of the individual regions contributing to the final catalog are given in the table http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/382/1639/regions.dat.

For further details of the surveys and data analysis procedures please refer to the published papers referenced above and other references contained therein.


Catalog Bibcode

2007MNRAS.382.1639H

References

A final non-redundant catalogue for the 7C 151-MHz survey
     Hales S.E.G., Riley J.M., Waldram E.M., Warner P.J., Baldwin J.E.
    <Mon. Not. R. Astron. Soc. 382, 1639 (2007)>
    =2007MNRAS.382.1639H

Provenance

This table was created by the HEASARC in October 2010 based on CDS table J/MNRAS/382/1639 files 7c.dat and regions.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, as recommended in the CDS ReadMe file for the 7C unified catalog. The CDS Dictionary of Nomenclature of Celestial Objects recommends either a truncated version of this naming convention, viz., '7C HHMM+DDMMa', or a higher-precision version, viz., '7C HHMMSS.ss+DDMMSS.ss', but the former may be ambiguous and the latter is not possible, given that the positions of these source is given to only 0.1 seconds of time in RA and 1 arcsecond in Declination.

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) error in the RA may be approximated by:

error(RA) (arcsec) = sqrt[1.02 + (32/SNR)2]

where SNR is the signal-to-noise ratio of the source.

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) error in the Declination may be approximated by:

error(Dec) (arcsec) = k cosec(Dec) x error(RA)

where k is a Declination-dependent constant with a value of approximately 1.0 around Dec = 70o, increasing to about 1.3 below Dec = 50o.

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). The 1-sigma errors in the beam-fitted flux density values may be approximated by:

error(Sbf) = Sbf * sqrt(0.032 + SNR-2)

Int_Flux_151_MHz
The integrated flux density Sint of the radio source at 151 MHz, in mJy (converted by the HEASARC from the Jy units used in the original table). The 1-sigma errors in the integrated flux density values may be approximated by:

error(Sint) = 1.5 * Sint * sqrt(0.032 + SNR-2)

For multi-component sources the SNR for the brightest component is used to estimate the error in Sint.

SNR
The signal-to-noise ratio (S/N) of the radio source, defined as the interpolated peak height of the source on the map (after subtraction of the local zero level), divided by the local noise.

Source_Extent
The extent of the source size in units of the local beam area.

Num_Local_Max
The number of individual peaks Nmax that were included in the flux integration region: thus, for a source with only one component, Nmax = 1 (and complex_source_id = 0).

Complex_Source_ID
A serial number Icomp denoting a particular complex source which has the same value for all the components (local maxima) which belong to that particular source, allowing the user to associate its individual components listed in the catalog. Thus, for a source with only one component, this parameter is set to 0 (and the number of local maxima Nmax to 1).

Field_ID
The B1950.0 equatorial coordinates (HHMMDD) of the 7C field (map) from which the source originated, with the '+' sign excluded, e.g. map 072245 denotes the sky coordinates 07h 22m +45o (B1950).

Region_Number
The region number is an alternative identifier for the 7C field (map) from which the source originated. This was not present in the original main 7C table (7c.dat), but the correspondence between it and the field_id parameter was taken from the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/382/1639/regions.dat. The HEASARC has assigned a region number of 78 to field_id values of '144060' and '152060' based on the note in the CDS ReadMe file for this table which states that region number 78 (field_id = '150060') is an amalgamation of data from two unpublished regions with these field_id values.


Contact Person

Questions regarding the UC7C151MHZ database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 29-Oct-2010