PMN (E0): Parkes-MIT-NRAO (PMN) 4850 MHz Radio Surveys; 1994 (19950121)
FILES:
pmntrop.e0 (13363 sources; Tropical survey: -29 < Dec < -9.5)
pmnsouth.e0 (23277 sources; Southern survey: -87.5 < Dec < -37)
CONTENTS: Parkes-MIT-NRAO 4850 MHz Radio Surveys; Griffith, Wright et al, 1994
DATASET: These files come in HyperSky dataset E-16, version 19950121. Availability on HyperSky CD-ROM: Vol. 2 (1995)
DESCRIPTION: These datafiles contain a total 36640 radio sources detected with the Parkes-MIT-NRAO (PMN) Tropical and Southern 4850 MHz surveys.
The Southern survey covers 2.50 sr and contains 23,277 sources to a flux limit which varies as a function of declination from 20 mJy at the southern survey limit to about 50 mJy at the northern limit. The survey increases the number of radio sources known in the area surveyed by a factor of about 5 over those found by either of the earlier Parkes or Molonglo surveys.
The Tropical survey covers 2.01 sr and contains 13,363 sources to a flux limit that is, typically, about 42 mJy but varies depending on declination. The survey was made using the Parkes 64 meter radio telescope with the NRAO multibeam receiver during 1990. The survey increases the number of known sources in the region surveyed by approximately a factor of 5.
The HyperSky file is based on the version of the catalog available through the U.S. National Space Sciences Data Center (NSSDC) as Astronomical Data Center (ADC) catalog #8027. The catalog is also distributed by the Stellar Data Centre (CDS), Strasbourg, France, as catalog VIII/27.
DATA: The HyperSky datafile contains the following data from the catalog:
POSITION: Right Ascension and Declination the catalog J2000 positions. Catalog positions were provided to an accuracy of 1 second in Right Ascension and 1" in declination.
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, users can display only those sources above a desired 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 source strengths. For the HyperSky catalog, the brightest source (S1 = 100053 mJy) is arbitrarily assigned the magnitude m1 = 1.0. Given this, any other source S2 can have its relative magnitude, m2, derived using the relation:
m2 = m1 + 2.5 * log10 (S1 / S2);
Or in this case:
m2 = 1.0 + 2.5 * log10 (100053 / S2);
In this system, the faintest catalog source (20 mJy) has a magnitude of 10.2. The following table summarizes the relation between magnitude and source strength for catalog extremes and intermediate magnitudes:
Magnitude Source Strength, mJy (+ examples)
----------|--------------------------------------------
1.0 100153 (brightest source; PMNJ0859-4730)
2.0 40000 (PMNJ1044-5938)
3.0 15000 (PMNJ1031-5520)
4.0 6100
5.0 2400
6.0 950
7.0 380
8.0 150
9.0 60
10.2 20 (faintest source)
With the above table, you can set HyperSky's limiting magnitude (for emission sources) to mask out catalog sources below a desired 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 PMN catalog; only the source strengths are fundamental catalog values.
The brightest source in the above table, PMJ0859-4730, matches a source identified in the PKSCAT90 database as Vela supernova remnant CTB31.
IDENTIFICATION: The PMN catalog designation is composed of the prefix "PMNJ", followed by the J2000 right ascension in hours and minutes, plus the declination in degrees and minutes.
COMMENTS: The comment lines following the identification contain the following information, where available, for each radio source:
* A line starting with "flux(4850 MHz)=", giving the source strength in milli-Janskys (mJy). The Jansky (Jy), originally called a flux unit, equals 1E-26 watt per square meter per hertz.
* A line containing the comment "extended?" if the catalog flags the source as "probably extended".
* A line starting with "flags:", followed by various single-letter flags from the PMN catalog, described below:
"G" indicates the source lies within 10 deg of the Galactic plane.
"M" indicates that the source lies within 2' of a source listed in the Molonglo 408 MHz catalog (Large et al. 1981) and is probably the same object.
"P" indicates that the source lies within 2' of a source listed in the PKSCAT90 database and is probably the same object.
"S" indicates that the source lies within 5 degrees of solar contamination from the telescope's sidelobes and the data listed may be of lower quality.
"Z" indicates a source which was observed within 6 deg of the Parkes telescope's zenith and has a flux < 60 mJy.
REFERENCES
I. The 4850MHz Surveys and data reduction
GRIFFITH M.R., WRIGHT A.E. : 1993
Astron. J. 105, 1666
II. Source catalog for the Southern Survey
WRIGHT A.E., GRIFFITH M.R., BURKE B.F., EKERS R.D. : 1994
Astrophys. J. Suppl. Ser. 91, 111
III. Source catalog for the Tropical Survey
GRIFFITH M.R., WRIGHT A.E., BURKE B.F., EKERS R.D.: 1994
Astrophys. J. Suppl. Ser. 90, 179