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MRC: Help

MRC - Molonglo Reference Catalog of Radio Sources


Overview

This catalog is a version of the 1990 issue of the "Molonglo Reference Catalog of Radio Sources" (MRC). The MRC is one of the largest homogeneous catalogs of radio sources, containing 12,141 discrete sources with flux densities greater than 0.7 Jy in the declination range +18.5 degrees to -85 degrees (1950 coordinates) and excluding regions within 3 degrees of the Galactic equator.

Catalog Bibcode

1981MNRAS.194..693L

References

The original MRC was published by Large M.I., Mills B.Y., Little A.G., Crawford D.F. and Sutton J.M., 1981, in Mon. Not. R. Astr. Soc., v194, pp693-704 and microfiches MN 194/1.

The revised MRC is described by Large M.I., Cram L.E. and Burgess A.M., 1991, in The Observatory, v111, pp72-75.


Description

The original MRC was published in 1981. It was re-issued in 1990 with the original B1950 coordinates supplemented by J2000 coordinates and an additional cross-reference flag. No other changes were made to the catalog.

The EXOSAT DBMS version of the catalog has been created from the 1990 release, but does not contain the J2000 coordinates as the DBMS provides facilities for automatically converting between coordinate systems. This version was prepared on 28th February 1992.

The summary of the original catalog read as follows.

"408-MHz survey observations made with the Molonglo Radio Telescope have been used to prepare a catalog of 12 141 discrete sources of listed flux density >= 0.7 Jy. The survey covers 7.85 sr of the sky defined by +18.5 (deg) >= dec(1950) >= -85.0 (deg), mod(b) >= 3 (deg). A few sources beyond the declination limits are also included. The catalog comprises celestial coordinates with standard error typically lying between 3 and 10 arcsec and 408-MHz flux densities with standard error typically lying between 4 and 10 per cent. Galactic coordinates, notes on source morphology and cross- references to the Parkes Catalogs are included. The overall source density is 1500/sr, corresponding to 0.001 per beam area. There are 7347 sources of listed flux density >= 1.00 Jy, at which level the catalog is substantially complete. The reliability is believed to be better than 99.9 per cent."


Parameters

Name
Recommended IAU name of the source based on the B1950 equinox coordinates. The first four characters are the hours and minutes of Right Ascension, and the last four the signed declination in tenths of a degree (unrounded). Column 9 contains the letters A, B, etc. denoting sources having the same eight- character IAU designation but decreasing flux density.

RA
The Right Ascension of the source.

Dec
The Declination of the source.

RA_Error
Standard error in Right Ascension in seconds of time.

Rascat
An asterisk ('*') in this field indicates that the values for the Right Ascension obtained from two or more independent transits are scattered more than expected.

Dec_Error
Standard error in declination in seconds of arc.

Decscat
An asterisk ('*') in this field indicates that the values for the declination obtained from two or more independent transits are scattered more than expected.

Flux
Flux density at 408 MHz in mJy.

Flux_Error
Standard error in flux density in mJy.

Fluxscat
An asterisk (*') in this field indicates that the values for the flux density obtained from two or more independent transits are scattered more than expected.

Morph1
The first of three morphology flags. These three fields contain details of the source type or morphology. If all three fields are blank there is no clear evidence of departure from a point source. The morphology codes are defined as follows:

   * A = Source with small-scale structure,
   * E = Extended source,
   * C = Complex extended source,
   * M = Multiple sources (within 8 arcmin of another),
   * N = Weak neighbouring sources.
  
Any of the codes can appear in any of the three fields. A given source can be assigned up to and including three codes.

Morph2
The second of three morphology flags. Refer to the description of 'Morph1' for details.

Morph3
The third of three morphology flags. Refer to the description of 'Morph1' for details.

Maps
This field either contains a 'J' or is blank. A 'J' indicates that an 843-MHz map of the source is available. See Jones P.A., 1989, PhD Thesis, University of Sydney or Jones P.A. and McAdam W.B. for further details.

Refs1
The first of two cross-reference flags. These two fields contain cross-references to other catalogs which include the source. The codes are defined as follows:

   * P = the source lies within 2 arcmin of a source in the Parkes Master
         Catalog (see Bolton J.G, Wright A.E. and Savage A., 1979,
         Aust. J. Phys. Astrophys. Suppl., v46 p1),
   * T = the source is discussed in the original MRC MNRAS paper,
   * S = see Schilizzi R.T. and McAdam W.B., 1975, Mem. R. Astr. Soc.,
         v79, p1.
   * M = see Clarke J.N., Little A.G. and Mills B.Y, 1976,
         Aust. J. Phys. Astrophys. Suppl., v40 p1,
   * C = see Cameron M.J., 1971, Mon. Not. R. Astr. Soc. v152, p439.
   * R = see Robertson J.G., 1973, Aust. J. Phys. v26, p403.
  
The S,M, and C references give Molonglo 408 MHz isophotes, which provide additional information and exemplify the use of the morphological types.

The R reference presents 408 MHz data on centroid position and total flux density.

Any of the flags can occur in either of the two fields. Obviously, a given source can have, at most, two flags. Where necessary, priority was assigned in the sense:

                        P > T > S > M > C > R
  

Refs2
The second of two cross-reference flags with the same meaning as 'Refs1'.

LII
Galactic longitude, as provided in the original MRC catalog, in degrees, with one decimal place.

BII
Galactic latitude, as provided in the original MRC catalog, in degrees, with one decimal place.


Contact Person

Questions regarding the MRC database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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