[ CATS home ] [ Back to CATS list ]
[ ftp ]
1990MNRAS.244..233Rees
1995MNRAS.274..447Hales+
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
============================================================================
Description:
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:
- P = Simple source with only one local maximum within the
source region (defined by the contour which encircles
the local maximum and is 2.5 times the local noise level).
The position is that of the peak flux brightness.
- C = Component or source associated with a single local
maximum within an integrated complex. The peak and
integrated flux for each such component represent
values for that component only, and the position is
that of the peak brightness. The components of a
complex are not grouped together in the revised list,
because it is ordered in right ascension.
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)
back to begining