RADIO_6C (E0): Sixth Cambridge Radio Survey of Selected Areas (19941112)
FILE: radio_6c.e0 (24209 entries)
CONTENTS: Sixth Cambridge Radio Survey Catalog of Selected Areas
DATASET: This file comes in HyperSky dataset E-8, version 19941112. Availability on HyperSky CD-ROM: Vol. 2 (1995)
DESCRIPTION: This datafile contains a 24209 sources from the SIXTH CAMBRIDGE (6C) SURVEY of selected areas. The survey was done at a frequency of 151.5 MHz, and covers portions of the northern sky. The source list was derived from radio maps centered on declinations of +41, +58, +75 and +90 degrees. All survey sources are contained in a large contiguous region which extends in declination from +90 to +30 degrees. The table below gives the approximate Right Ascension ranges covered as a function of declination:
Dec Range RA Range
-----------|-----------
+90 to +66 0h to 24h
+66 to +48 6h to 18h
+48 to +30 8h 40m to 17h 20m
A wide-scale view showing most of this region can be obtained by using a full-screen 60-degree HyperSky field centered at RA=13h and Dec=+77.5 deg. Peak 151 MHz flux densities range from 0.13 to 90.8 Jy. The HyperSky catalog is based on a copy of the 6C source list obtained through NRAO.
DATA:
The HyperSky datafile contains the following data from the catalog:
POSITION: Right Ascension and Declination are based on the 1950 source list positions, precessed to equinox 2000. Source list positions were provided to an accuracy of 0.1 second in Right Ascension and 1" in declination.
MAG: No magnitudes or equivalents were provided in the source list. 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 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 source strengths. For the HyperSky catalog, the brightest source (S1 = 90.8 Jy) 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);
In this system, the faintest catalog source (0.13 Jy) has a magnitude of 8.1. The following table summarizes the relation between magnitude and flux strength for 6C catalog extremes and intermediate magnitudes:
Magnitude Peak Flux (Jy)
----------|----------------------
1.0 90.8 (brightest source)
1.5 54.8
2.0 38.4
3.0 13.8
4.0 5.5
5.0 2.3
6.0 0.92
7.0 0.36
8.0 0.15
8.1 0.13 (faintest source)
With the above table, a user can set HyperSky's limiting magnitude (for emission sources) to mask out sources below a desired strength. Except for this use, derived source magnitudes have NO significance. It should be emphasized again that magnitudes are NOT provided in the original source list; only flux strengths are fundamental values.
IDENTIFICATION: The derived source name, constructed from the equinox 1950 RA, Dec HHMM+DDMM. These names have been generated for the HyperSky catalog; they were NOT provided in the 6C source list.
COMMENTS: The comment line contains the following information, provided for each radio source identification:
* A line beginning with "f(151)=" giving the radio source strength (peak flux density) measured at a frequency of 151.5 megahertz. Measurement units are janskys (originally flux units). One jansky equals 1E-26 watt per square meter per hertz.
* In parentheses, if available, following the above value is the integrated flux density for the source, in janskys.
REFERENCES:
J.E. Baldwin, R.C. Boysen, S.E.G. Hales, J.E. Jennings, P.C. Waggett,
P.J. Warner, and D.M.A. Wilson
1985, MNRAS, 217, 717.
S.E.G. Hales, J.E. Baldwin, and P.J. Warner
1988, MNRAS, 234, 919.
S.E.G. Hales, C.R. Masson, P.J. Warner, and J.E. Baldwin
1990, MNRAS, 246, 256.
S.E.G. Hales, C.J. Mayer, P.J. Warner, and J. E. Baldwin
1991, MNRAS, 251, 46.