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Revised source list for the Rees 38-MHz survey (Hales+ 1995)

A revised machine-readable source list for the Rees 38-MHz survey.
Hales S.E.G., Waldram E.M., Rees Nick, Warner P.J
Mon. Not. R. Astron. Soc., submitted (1995)
A deep 38-MHz radio survey of the area declination > +60 degrees.
Rees Nick
Mon. Not. R. Astron. Soc. 244, 233 (1990)
1990MNRAS.244..233R ============================================================================


We present a revised machine-readable source list for the Rees 38-MHz (or '8C') survey with improved positions and no redundancy. The Rees 38-MHz survey covers an area of about 1 sr north of declination +60 degrees. The angular resolution is 4.5 x 4.5cosec(dec) arcmin**2 and the limiting flux density over much of the survey area is about 1 Jy. Both of these figures are an improvement by nearly an order of magnitude on previous surveys at this frequency. Users of these data should consult and cite the original survey paper by Rees as primary reference (=1990MNRAS.244..233R) with the present publication (=1995MNRAS.submitted) as a supplementary revision. The recommended style of reference is thus : "The revised Rees 38-MHz survey (Rees 1990, catalogue revised Hales et. al 1995)." Note that for interest the source list includes data on some sources at declinations lower than +60 degrees, but that the right ascension coverage is not complete below +60 degrees.
  File Name      Lrecl       Records     Explanations
  8C.dat           57          5859     38-MHz data on 5859 sources

Byte-by-byte Description of file: 8C.dat
 Bytes Format  Units   Label    Explanations
 1-  2  I2     h       RAh      Right Ascension B1950 (hours)
 4-  5  I2     min     RAm      Right Ascension B1950 (minutes)
 7-  8  I2     s       RAs      Right Ascension B1950 (seconds)
    10  A1     ---     DE-      Declination B1950 (sign)
11- 12  I2     deg     DEd      Declination B1950 (degrees)
14- 15  I2     arcmin  DEm      Declination B1950 (arcminutes)
17- 18  I2     arcsec  DEs      Declination B1950 (arcseconds)
    20  A1     ---     SType   *[PC] Source type
22- 28  F7.1   ---     PEAK    *Peak brightness (Jy/beam)
30- 36  F7.1   Jy      INTEG   *Integrated flux density (Jy)
38- 42  F5.1   ---     Size    *Size (integrated area/synth beam)
44- 50  F7.1   ---     SigNo   *Signal-to-noise ratio of detection
53- 57  A5     ---    AtlasNum *Number of contour plot in Rees 1990
00 00 15  74 59 34 P     3.7     4.2   1.1    12.6   3-11
00 01 04  62 30 40 P     5.3     6.5   1.3     7.0   2-11
00 01 19  65 57 12 P     3.3     4.0   1.2     6.4   2-11
00 01 47  76 39 19 P     1.4     2.1   1.5     7.4   4-11
Note on SType: Note on PEAK:
Peak brightness of source or component, measured in Jy/(beam area). The area of the synthesised beam is 4.5 x 4.5cosec(dec) arcmin**2.
Note on INTEG:
Integrated flux density of source or component.
Note on Size:
This is an indicator of the extent of the source and is the ratio of the integration area of the source to the area of a synthesised beam, calculated using the same integration level. Thus, size = 1 indicates a point source, size << 1 indicates some over-resolution due to noise effects, and size <> 1 an apparently extended source. Most sources appear slightly extended because of distortions created by the ionosphere. Remember that the survey is confusion limited!
Note on SigNo:
The signal-to-noise, ie: the ratio of the peak brightness to the local noise level calculated at the position of the source. The revised list contains only sources or components with signal-to-noise >= 5.0. It excludes the components with signal-to-noise < 5.0 listed in Rees 1990 for some complexes.
Note on AtlasNum:
This gives the number of the contour plot on which the source appears in the atlas provided in Rees 1990, to enable the user to check the appearance and environment of the source. The atlas may be obtained in preprint form - see paper for details.
Discussion of the units used for peak brightness: The beam is not of constant size, the resolution being 4.5 x 4.5cosec(dec) arcmin**2. The point of quoting the peak brightness in Jy/beam is that, for a source which is not significantly resolved or distorted by ionospheric effects, the peak brightness in those units will give a reasonable estimate of the flux density of the source (and be numerically comparable to the integrated flux density in Jy). The provided on size also ties in with this idea by comparing the integration area of a source to the area of a synthesised beam.
The original paper by Rees contains much discussion about the relative merits of peak brightness and integrated flux density as estimates of a source flux density, including consideration of the behaviour of their ratio; all this hinges on the idea of flux being smeared out w.r.t. the theoretical synthesised beam, so that the concept of a beam area is crucial to the discussion.
(From Sally Hales [Cambridge, UK] 30-NOV-1994) up back to begining