J/A+AS/58/39 1412 MHz catalogue of Westerbork survey. II (Windhorst+, 1984)
A deep Westerbork survey of areas with multicolor Mayall 4 m plates.
II. Optical identifications.
Windhorst R.A., Kron R.G., Koo D.C.
<Astron. Astrophys. Suppl. Ser. 58, 39 (1984)>
=1984A&AS...58...39W 1984A&AS...58...39W
ADC_Keywords: Radio sources ; Surveys ; Cross identifications
Keywords: radio sources: general - astrometry - galaxies: radio - cosmology
Abstract:
A deep multicolor optical identification program is presented for a
complete sample of 302 radio sources that were observed with the
Westerbork Synthesis Radio Telescope within 5.52°2 down to
S1.4GHz≳0.6mJy (5σ). Optical identifications are made from
multicolor prime focus plates taken with the Kitt Peak 4 meter
telescope in the passbands U,J,F and N with approximate respective
limiting magnitudes of ∼23.3, 23.7, 22.7 and 21.1. The astrometry
has systematic errors smaller than 0.2"-0.3", while the random errors
are of order 0.4". The agreement between the radio and optical
coordinate frames is on average better than 0.25". Identifications are
based on positional coincidence using the likelihood ratio method. For
171 out of the 302 radio sources likely identifications are proposed
with an a posteriori identification percentage of 53%, 14 expected
spurious objects (or 5% of all radio sources), while not more than 4
identifications have been missed. The sample reliability is 92% and
its completeness 98%. About 20% of the identifications are stellar
objects, the remaining have extended images or are too faint to be
classified. About 15% of the identifications appear in possible
clusters. The identification statistics are roughly constant from
field to field, except for the Hercules 2 field which has an
unusually high identification fraction (74%). The identification
fraction is presented as a function of 21 cm flux density and limiting
magnitude, and amounts to 15% for 1≲S1.4GHz≲100mJy down to the
Palomar Sky Survey limit and 29% down to the effective 48" Schmidt
limit. For S1.4≲100mJy the identification fraction remains roughly
constant with flux density, contrary to the prediction of higher
fractions by some models for cosmological evolution. The magnitude
distributions for galaxies plus objects of unknown type generally
increase towards fainter magnitudes; the quasar magnitude
distributions are also increasing but not as steeply as for the radio
galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 46 List of Mayall prime focus plates used
table4a.dat 80 171 List of optical identifications in the complete
sample
table4b.dat 80 41 List of identifications NOT in a complete sample
notes.dat 80 119 Individual notes
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See also:
VIII/62 : The Westerbork Northern Sky Survey (Leiden, 1998)
J/A+AS/58/1 : 1412 MHz catalogue of Westerbork survey (Windhorst+, 1984)
J/A+A/35/393 : Westerbork Second Deep Survey (Katgert, 1974)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Field Field designation
8- 9 I2 h RAh Right ascension (1950)
11- 12 I2 min RAm Right ascension (1950)
14- 15 I2 s RAs Right ascension (1950)
17 A1 --- DE- Declination sign (1950)
18- 19 I2 deg DEd Declination (1950)
21- 22 I2 arcmin DEm Declination (1950)
24- 25 I2 arcsec DEs Declination (1950)
27- 30 I4 --- MPF Mayall prime focus plate number
32- 37 A6 --- Emuls Emulsion
39- 43 A5 --- Filter Filter
45- 47 I3 min Texp Exposition time
49- 52 A4 --- HA Hour angle (end exposure)
54- 57 F4.2 --- Airmass Airmass (mid-exposure)
59- 62 F4.2 arcsec Seeing Seeing (in σ/")
64- 76 A13 --- Com Comments/observers (1)
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Note (1): Observers are R. Kron or K. Koo unless stated otherwise
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Byte-by-byte Description of file: table4a.dat table4b.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- WSTB Westerbork designation (1)
7 A1 --- m_WSTB [*ABC] Multiplicity index on Name (2)
9- 10 I2 h RAh Right ascension (1950.0)
12- 13 I2 min RAm Right ascension (1950.0)
15- 19 F5.2 s RAs Right ascension (1950.0)
22 A1 --- DE- Declination sign (1950.0)
23- 24 I2 deg DEd Declination (1950.0)
26- 27 I2 arcmin DEm Declination (1950.0)
29- 32 F4.1 arcsec DEs Declination (1950.0)
34- 38 F5.1 arcsec oRA Average offset in right ascension (3)
40- 44 F5.1 arcsec oDE Average offset in declination (3)
47- 51 F5.2 --- R Normalized position difference
54- 59 F6.2 --- LR Likelihood ratio
64- 65 A2 --- ID Identification type (4)
67- 68 A2 --- Morph Morphology (5)
71- 72 A2 --- Env Environment (6)
75- 76 A2 --- Note Notes (7)
79- 80 I2 --- q_ID Identification code (8)
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Note (1): Westerbork designation that consist of the Westerbork Survey number,
which is 52 for SA57, 53 for Hercules, 54 for SA68 and 55 for Lynx,
and a sequence number, in order of increasing RA.
WSTB 52W NNA, WSTB 53W NNA, WSTB 54W NNA and WSTB 55W NNA in Simbad.
Note (2): An * indicates that for this source multiple components were found,
which are listed directly below, and are labelled A, B, C, etc. A
detectable central component is always labelled "C". Generally, A and
B are the western and easternmost components
Note (3): the offsets are defined as:
oRA = RArad - RAopt - <RArad - RAopt>field
oDE = DErad - DEopt - <DErad - DEopt>field
Note (4): Identification type:
G: galaxy (extended image)
Q: stellar object (not necessarily a quasar)
S: spectroscopically confirmed star
?: object, but too faint to classify
Note (5): For objects ≳4.0mag above the plate limits we consider:
CD: first ranked galaxy in a cluster or group
EL: elliptical or lenticular galaxy
SP: spiral galaxy
PC: peculiar (explained in the notes)
For fainter objects we use:
CM: compact, high surface brightness
FZ: low surface brightness, fuzzy galaxy
Note (6): Environment:
CL: possible cluster, with ≥5 apparently associated galaxies
GR: group of galaxies, with fewer apparently associated objects.
DB: double galaxy. Another galaxy within one magnitude and one diameter.
Note (7): Number refers to notes on the optical identification:
1: object in stellar, but not blue
2: blue object is of (unusually) high surface brightness, or
sometimes a red object is of (unusually) low surface brightness.
3: the identification has a very close companion or an optical jet.
4: the identification is optically variable
5: two or more possible identifications were found in the various
radio components of this double or complex radio source.
Table4a.dat lists the identification that we believe to be
correct one from all available data: table4b.dat gives the other
possible identifications. These cases are discussed individually
in the notes.
6: other notes on the optical object listed in the notes.dat file
7: detected s X-ray source (Katgert et al., 1983ApJ...275....1K 1983ApJ...275....1K)
Capitals refers to notes on the radio source morphology, if relevant
for the optical identification. Here the additional 25 objects are
classified, for which the likelihood ratio analysis did not give an
identification, while still a very likely optical candidate was found.
A: Very extended radio sources (doubles with angular sizes ≳30")
B: Head-tail and asymmetrical or complex radio sources
C: Sources evidently misaligned with the centre of the optical image
D: Diffuse radio sources with a spectroscopically confirmed candidate
E: Very low surface brightness radio sources without spectroscopy
*: indicates a note detailed in "notes.dat" file
Note (8): Identification code:
0: reliable identification in the conservative sample of 146 objects
-1: likely identification in the additional sample of 25 objects.
Reason is given in column note and in the notes of notes.dat file
1: reliable identification but not in the complete optical sample
2: reliable identification but not in the complete radio sample
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- WSTB Westerbork designation
8- 80 A73 --- Note Text of the Note (1)
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Note (1): Individual notes are given for optical objects that could not be
adequately described in notes 5-8. Notes are also given for the 25
extended or complex radio sources for which the identification was not
straightforward. For this latter subsample we classify the suggested
identification as solid, very likely, likely or possible. The 21cm
information is taken from Paper I, (Windhorst et al., Cat.
J/A+AS/58/1) where contours of extended and complex radio sources
are given, in which the positions of the optical objects from the
current paper are marked with crosses. The surface brightness of the
radio sources was noted from these contour plots or from a comparison
between the contour plots of the high resolution and the low
resolution 21cm maps of Paper I and the 50cm maps of Windhorst and
Oppe (1984; Paper IV, submitted). For extended sources the western-
and eastern-most components are referred to as A and B respectively,
while any detectable central component is called C. All 50cm radio
information (including spectral index α=-logSv/logv) is taken
from Paper IV. For a few sources that were asymmetrically resolved at
21cm a better position was obtained at 50cm, which in a few doubtful
cases clarified the situation. All additional optical information
(photometry, spectra) is taken from Paper III (Kron et al.,
1985A&A...146...38K 1985A&A...146...38K), unless stated otherwise.
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History:
OCR'ed by H. Andernach (), proofread at CDS.
Errors in table4a and table4b corrected on 28-Jul-2001
1 error in table4b corrected on 02-Aug-2001
1 further error in table4b corrected on 02-Jun-2004
References:
Windhorst et al., Paper I 1984A&AS...58...39W 1984A&AS...58...39W, Cat. J/A+A/58/1
Windhorst et al., Paper III 1985A&A...146...38K 1985A&A...146...38K
(End) Patricia Bauer [CDS] 10-May-2001