GAL_5GHZ (E0): Catalog of 5 GHz (6cm) Galactic Plane Sources (19950130)
FILES: gal_5ghz.e0 (915 sources)
CONTENTS: Catalog of 5 GHz (6cm) Galactic Plane Sources; Haynes et al, 1979
DATASET: This file comes in HyperSky dataset E-19, version 19950130 Availability on HyperSky CD-ROM: Vol. 2 (1995)
DESCRIPTION: This datafile contains a total of 915 sources found in a 5 GHz (6cm) survey of the galactic plane carried out with the Parkes (Australia) 64-meter radio telescope. Sources with a peak beam brightness temperature of at least 0.2 K (Kelvin) above the background are included, except in confused regions; an 0.2 K point source corresponds to 0.26 Jy.
The survey covers the galactic planar region (galactic latitude range -2 < b < 2) extending from galactic longitude l=190 (northern Orion) through l=0 (the galactic center in Sagittarius) to l=40 (Aquila). The catalog contains only a few scattered sources from Orion to l=280 (Vela). Source density is much more solid from Vela on to Aquila, at which point cataloged sources end abruptly.
The uniform nature of the observing and analysis techniques used throughout the survey provides a good basis for studying discrete continuum radio sources in the galactic plane.
The HyperSky file is based on the catalog version available from the the U.S. National Space Sciences Data Center (NSSDC) as Astronomical Data Center (ADC) catalog #8020. The catalog is also available from the Stellar Data Centre (CDS), Strasbourg, France, as catalog VIII/20.
DATA: The HyperSky datafile contains the following data from the catalog:
POSITION: The catalog B1950 Right Ascension and Declination, precessed to equinox 2000. According to the catalog, source positional accuracy is 30" (r.m.s.)
MAG: No magnitudes or equivalents were provided in the catalog. A set of artificial magnitudes is provided, however, in the HyperSky catalog strictly to allow use of HyperSky's limiting-magnitude controls. In this way, you can display only those sources above a desired 5GHz flux threshold. The artificial magnitude system is based on the relation (from Pogson) used to define visual magnitudes:
m1 - m2 = 2.5 * log10 (S1/S2)
where { m1, m2 } are magnitudes, and { S1, S2 } are flux strengths. For the HyperSky catalog, the brightest source (S1 = 69.4 Jy) is arbitrarily assigned the magnitude m1 = 1.0. Given this, any other source S2 can have its relative magnitude, m2, derived with the relation:
m2 = m1 + 2.5 * log10 (S1 / S2);
Or in this case:
m2 = 1.0 + 2.5 * log10 (69.4 / S2);
In this system, the faintest catalog source (0.24 Jy) has a magnitude of 7.2. The following table summarizes the relation between magnitude and source strength for catalog extremes and intermediate magnitudes:
Magnitude Source 5GHz Strength, Jy
----------|-------------------------------------------
1.0 69.4 (strongest source: G359.9-0.1)
1.9 29.0
3.0 17.8
4.0 4.13
5.0 1.78
6.0 0.68
7.0 0.28
7.2 0.24 (weakest source)
With the above table, you can set HyperSky's limiting magnitude (for emission sources) to mask out catalog sources below a desired flux strength. Except for this use, the derived source magnitudes have NO significance. It should be emphasized again that the magnitudes are NOT provided in the catalog; only the source flux strengths are fundamental catalog values.
IDENTIFICATION: No source names were provided in the catalog. For the HyperSky datafile, source names have been constructed from the catalog galactic longitude and latitude using a "G", followed by the concatenation of galactic latitude and longitude, both in degrees, to 0.1 degree accuracy.
COMMENTS: The comment lines following the identification contain the following information, where available, for each source:
* A line giving the peak brightness temperature of the source, in degrees Kelvin.
* A line giving the source flux density at 5 GHz (6cm). Measurement units are janskys (Jy, originally flux units). One jansky equals 1E-26 watt per square meter per hertz.
* A line giving the angular source size, in arcminutes. The angular size, when provided, refers to the full width of the source measured in the galactic longitude and latitude directions. It is intended only as a rough indication for sources much broader than the beam size; in very confused regions no attempt was made to assess the sizes of component sources.
* A line containing a brief comment about the source morphology and its association with known supernova remnants (from the compilation of Clark and Caswell, 1976), or HII regions (from Wilson et al, 1970). The abbreviation C refers to "compact", E refers to "extended" and PA refers to "part".
REFERENCES
Haynes R.F., Caswell J.L., Simons L.W.J.
Aust. J. Phys. Astrophys. Suppl 48, 1 (1979)