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SNRGREEN: Help

SNRGREEN - Green Catalog of Galactic SNRs (December 2001 Version)


Overview

This catalog lists all galactic supernova remnants (SNRs) known, and is the December 2001 updated version of the catalogues of Galactic SNRs presented in detail in Green (1984, 1988), in summary form in Green (1991, 1996), and on the World-Wide-Web (versions of July 1995, August 1996, September 1998, and August 2000). [Note that the version published in Green (1996) was produced in 1993.]

This December 2001 version of the catalogue contains 231 SNRs, which is 6 more than listed in the previous version, which this version replaces in the HEASARC database. The basic summary data included in this catalogue for each SNR are its designation, position, angular size (in arcminutes), type, flux density at 1 GHz, spectral index, and any other names by which it is known. Notes on these parameters, on possible remnants not included, and on questionable SNRs that are listed in this catalogue, are given in the full version of the catalogue on the World-Wide-Web at http://www.mrao.cam.ac.uk/surveys/snrs/

It should be noted that there are serious selection effects which apply to the identification of Galactic SNRs (see Green 1991), so that great care should be taken if these data are used in statistical studies.


Catalog Bibcode

<VII/227/snrs.dat>

References

Green, D.A., MNRAS, 209, 449 (1984) =1984MNRAS.209..449G (Paper I).

Green, D.A., ApSS, 148, 3, (1988)   =1988APSS..148....3G (Paper II).

Green, D.A., PASP, 103, 209 (1991)  =1991PASP..103..209G (Paper III).

Green D.A., 1996, in Supernovae and Supernova Remnants, (Proceedings of IAU
Colloquium 145), eds McCray R. & Wang Z., (Cambridge University Press), p. 419
(Paper IV).

Green D.A., 1998, A Catalogue of Galactic Supernova Remnants, 1998 September
version <Mullard Radio Astronomy Observatory, Cambridge, United Kingdom (1998)>

Green D.A., 2000, A Catalogue of Galactic Supernova Remnants, 2000 August
version <Mullard Radio Astronomy Observatory, Cavendish Laboratory, Cambridge,
United Kingdom (2000)>

Green D.A., 2001, A Catalogue of Galactic Supernova Remnants, 2001 December
version <Mullard Radio Astronomy Observatory, Cambridge, United Kingdom
(2001)>

Provenance

This version of the Green Catalog of Galactic Supernova Remnants was created at the HEASARC in March 2002 based on the Catalogue of Galactic Supernova Remnants, 2001 December version <Mullard Radio Astronomy Observatory, Cambridge, United Kingdom (2001)> obtained from the CDS (their catalog ftp://cdsarc.u-strasbg.fr/pub/cats/VII/227/). It is referred to by the author as the 2001 December version.

Parameters

Name
The catalog designation of the remnant given with the `SNR` prefix and the LII and BII coordinates to the nearest 0.1 degrees in the way recommended by the Dictionary of Astronomical Nomenclature and recognized by SIMBAD. Notice that this supercedes the `old' nomenclature which used a 'G' prefix (and which was in fact used in the CDS table from which this present database was constructed).

RA
The Right Ascension of the remnant. The accuracy of the quoted positions depends on the size of the remnant; for small remnants they are to the nearest few seconds of time and the nearest minute of arc for RA and Dec, respectively, but for larger remnants they are rounded to coarser values. They are in every case sufficient to specify a point within the boundary of the remnant. These coordinates are generally deduced from radio maps rather than from X-ray or optical observations, and were given in the original catalog in J2000 equator.

Dec
The Declination of the remnant. The accuracy of the quoted positions depends on the size of the remnant; for small remnants they are to the nearest few seconds of time and the nearest minute of arc for RA and Dec, respectively, but for larger remnants they are rounded to coarser values. They are in every case sufficient to specify a point within the boundary of the remnant. These coordinates are generally deduced from radio maps rather than from X-ray or optical observations, and were given in the original catalog in J2000 equator.

LII
The galactic longitude of the remnant.

BII
The galactic latitude of the remnant.

Major_Diameter
The major diameter of the remnant, in arcminutes. The angular size information is usually taken from the highest resolution radio map available, although, for some barely resolved sources that are thought to be SNRs, the only available size is that from Gaussian models after deconvolution with the observed beam size. The boundary of most remnants approximates reasonably well to a circle or an ellipse. A single value (placed in the major diameter field) is quoted for the angular size of the more nearly circular remnants, being the diameter of a circle with an area equal to that of the remnant, but, for elongated remnants, both major and minor diameters are given, these being the major and minor axes of the remnant boundary modeled as an ellipse. In a few cases an ellipse is not a satisfactory description of the boundary of the object (refer to the description of the individual object given in the full catalogue entry in the World-Wide Web version of the SNR Catalog at http://www.mrao.cam.ac.uk/surveys/snrs/ ), although an angular size is still quoted for information. For `filled-centre' remnants, the size quoted is for the largest extent of the observed radio emission, not, as at times has been used, the half-width of the centrally brightened peak.

Minor_Diameter
The minor diameter of the remnant, in arcminutes. The angular size information is usually taken from the highest resolution radio map available, although, for some barely resolved sources that are thought to be SNRs, the only available size is that from Gaussian models after deconvolution with the observed beam size. The boundary of most remnants approximates reasonably well to a circle or an ellipse. A single value (placed in the major diameter field) is quoted for the angular size of the more nearly circular remnants, being the diameter of a circle with an area equal to that of the remnant, but, for elongated remnants, both major and minor diameters are given, these being the major and minor axes of the remnant boundary modeled as an ellipse. In a few cases an ellipse is not a satisfactory description of the boundary of the object (refer to the description of the individual object given in the full catalogue entry in the World-Wide Web version of the SNR Catalog at http://www.mrao.cam.ac.uk/surveys/snrs/ ), although an angular size is still quoted for information. For `filled-centre' remnants, the size quoted is for the largest extent of the observed radio emission, not, as at times has been used, the half-width of the centrally brightened peak.

Flag_Major_Diameter
This flag is set to '?' if there is uncertainty in the quoted angular size information.

Type
The morphological type of the SNR, either "S", "F" or "C" according to whether the remnant shows a "shell", "filled-center" or "composite" (or "combination") radio structure, respectively, (or "S?", "F?" or "C?", respectively, if there is some uncertainty), or "?" in several cases where an object is conventionally regarded as an SNR even though its nature is poorly known or not well understood.

Limit_Flux_1_GHz
This flag is set to '>' if the quoted 1 GHz flux density is a lower limit.

Flux_1_GHz
The flux density of the remnant at 1 GHz, in milliJanskies (mJy). This is not a measured value, but that deduced from the observed radio frequency spectrum of the source. The frequency of 1 GHz is chosen because flux density measurements at frequencies both above and below this value are usually available.

Flag_Flux_1_GHz
This flag is set to '?' if the quoted 1 GHz flux density is considered uncertain.

Spectral_Index
The radio spectral index {alpha} where S({nu}), the flux density at frequency nu, is proprtional to {nu}^-{alpha}. The spectral index of the integrated radio emission from the remnant is either a value quoted from the literature, or one deduced from the available integrated flux densities of the remnant. For several SNRs a simple spectral model is not adequate to describe their radio emission, either because the spectral index varies across the face of the remnant or because the integrated spectrum is curved, and in these cases the parameter flag_spectral_index (q.v.) is set to 'V'. In some cases, for example where the remnant is highly confused with thermal emission, the parameter flag_spectral_index (q.v.) is set to '?' since either no value can be deduced with any confidence, or only an uncertain value can be deduced.

Flag_Spectral_Index
This flag is set to 'V' if a simple spectral model is not adequate to describe the remnants's radio emission, either because the spectral index varies across the face of the remnant or because the integrated spectrum is curved, or is set to '?' for cases where the remnant's emission is highly confused with thermal emission, so that either no value can be deduced with any confidence, or only an uncertain value can be deduced.

Alt_Names
Up to three alternate commonly used name for the remnant. A name that is given in parentheses indicates that the remnant is only a part of the source. For some objects, notably the Crab Nebula, not all common names are given.

Class
The BROWSE classification code populated using the type parameter.


Contact Person

Questions regarding the SNRGREEN 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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