J/MNRAS/246/110 7C survey of radio sources at 151 MHz (McGilchrist+ 1990)
The 7C survey of radio sources at 151 MHz - two regions centred at
RA 10h 28, Dec. 41 and RA 06h 28, Dec. 45
McGilchrist M.M., Baldwin J.E., Riley J.M., Titterington D.J.,
Waldram E.M., Warner P.J.
<Mon. Not. R. Astron. Soc. 246, 110 (1990)>
=1990MNRAS.246..110M 1990MNRAS.246..110M
ADC_Keywords: Radio sources ; Surveys
Abstract:
The 7C survey of radio sources is being made with the Cambridge
Low-Frequency Synthesis Telescope at 151MHz, with an angular
resolution of 70x70cosecδ.arcsec2. We present the results from
one part of of this survey covering 0.144sr in two areas of sky
centred at RA=10h28min, DE=41° and RA=06h28min, DE=45° and
reaching a limiting flux density of 50mJy. A list of the positions,
flux densities and angular sizes of 4723 sources is presented; the
position errors are in the range 1-3arcsec for sources with flux
densities greater than 500mJy, and the flux density errors are
typically 18mJy. About 10 per cent of the sources have apparent
angular sizes greater than 60arcsec. The derived source counts are as
accurate as those presently available at 405 and 1400MHz and show
similar behaviour; in particular the convergence slopes are the same.
The median spectral index between 151 and 408MHz remains constant at
∼0.9 between 10 and 0.5Jy at 151MHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 83 4723 Catalogue
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See also:
VIII/84 : A final non-redundant catalogue for 7C 151-MHz survey (Hales+ 2007)
J/A+AS/110/419 : 7C survey of radio sources (Visser+, 1995)
J/MNRAS/282/779 : 7C 151-MHz survey of region 9-16h 20-35deg (Waldram+ 1996)
J/MNRAS/294/607 : 7C(G) 151MHz survey of the Galactic plane (Vessey+ 1998)
J/MNRAS/298/637 : 7C 151MHz survey of 3 regions (Pooley+, 1998)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (B1950)
4- 5 I2 min RAm Right ascension (B1950)
7- 11 F5.2 s RAs Right ascension (B1950)
13 A1 --- DE- Declination sign (B1950)
14- 15 I2 deg DEd Declination (B1950)
17- 18 I2 arcmin DEm Declination (B1950)
20- 24 F5.2 arcsec DEs Declination (B1950)
26- 31 F6.3 Jy S151MHz Flux density at 151MHz
33- 38 F6.2 arcsec Size ? Angular size
40- 42 I3 deg PA [0/360]? Position angle
44- 46 I3 --- Npix ? Number of pixel used when calculating an
integrated flux density
48- 50 A3 --- MType Morphological type (1)
51 A1 --- n_MType [.?%#+*] Note on MType (2)
53 I1 --- Field [1/6] Field number (3)
55- 59 F5.3 --- Att Primary-beam attenuation
61- 65 F5.3 --- Dep ? Depression in the height of the beam due to
geometric and chromatic aberration
67- 72 F6.3 Jy PixMax ? Value of the highest pixels in the source,
in Jy/beam (4)
74- 75 A2 --- mPos Method used to determine the position (5)
77- 78 A2 --- n_S151MHz Method used to determine the flux density (6)
80- 81 A2 --- n_PA Method used to determine the angular size and
position angle (7)
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Note (1): the morphological type is summarized as follows:
PT: point
E: extended
EC: extended complex
DE: equal double
DUn: unequal double, the flux densities of the components being in the
ratio n:1
DC: double complex
HT head tail
Note (2): the following symbols are used:
.: firm classification
?: uncertain classification
%: slightly confused but firm classification
#: slightly confused, uncertain classification
+: confused but firm classification
*: confused, uncertain classification
Note (3): the numbers correspond to the following fields:
1: 0647+45
2: 0608+45
3: 1004+46
4: 1046+46
5: 1046+36
6: 1012+36
Note (4):
Value before correction for primary beam and without allowing for the
depression of the peak value of synthesized beam. If there is more
than one peak in the source, the average of the highest pixel values
is given.
Note (5): the methods are summarized as follows:
Dy: The position, and flux density, are found from an iterative
least-squares fit to the synthesized beam. The algorithm runs
automatically and is used for points sources; it is not
suitable for complex sources.
Pr: The data around the peak are interpolated on to a much finer grid,
and the position of the maximum on this fine grid is taken; if a
source has more than one peak, the position adopted is the
unweighted mean of all the peak positions
Us: For a very complex source, the position given is that at which the
optical identification is most likely to be found.
Note (6): the methods for the determinations of the flux density are:
Dy: see Note(5) above
I: The pixels above a certain level are summed; the sum is converted
to a flux density using an appropriate normalization factor.
P: The pixels above a certain level are summed; in addition the
immediate neighbours of the outmost points are included. The sum
is converted to a flux density using an appropriate normalization
factor.
Sf: A rotationally symmetric representation of the synthesized beam
is fitted to the source profile with height and zero-level as the
only parameters; pixels with values substantially different from
those expected are not included in the fitting procedure.
Cn: The area covered by the source is CLEANed down to the noise level,
using the local synthesized beam as the dirty beam; the flux
density is the sum of the clean components.
Note (7): the methods for the determinations of the size are:
Us: The user selects two points on a contour map of the source. The
angular size is the angular separation of these points and the
position angle is that of the line joining them. For complex
sources the size is generally the largest angular size; for those
with only one peak it is typically the full width at half
maximum in the direction of maximum extension, corrected for
beam broadening.
a: This is only used for sources with two or more peaks. The angular
size is the angular distance between the two most widely peaks;
the position angle is that of the line joining them.
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History:
From H. Andernach (catalog #A025 in his list)
(courtesy S.E.G.Hales)
(End) Patricia Bauer [CDS] 09-Mar-1999