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I/169 Construction of Extragalactic Reference Frame (Argue+ 1984)
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A Catalog of Selected Compact Radio Sources for the Construction of an
Extragalactic Radio/Optical Reference Frame
Argue A.N., de Vegt C., Elsmore B., Fanselow J., Harrington R.S., Hemenway
P., Johnston K.J., Kuehr H., Kumkova I.I., Niell A.E., Walter H.G.,
Witzel A.
<Astron. and Astrophys., 130, 191 (1984)>
=1984A&A...130..191A
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ADC_Keywords: Positional data; Radio sources
Description:
This catalog was compiled to provide accurate positions for selected
strong, compact extragalactic radio sources proposed for establishing an
almost inertial reference frame against which the motions of Earth,
galactic objects, and spacecraft may be measured. It is also intended to
define sources for which precise optical positions should be determined
in order to relate its established reference frame with the fundamental
optical system of the FK5. Astrometric data for 233 compact radio sources
having identified optical counterparts are given. The data listed for each
source are source identification, equatorial position (J2000.0), mean
positional errors, object classification (galaxy, BL Lacertae object, QSO),
visual magnitude, redshift, 5-GHz flux density, and observation and remarks
codes. The data were computerized at the Astronomical Data Center,
NASA/GSFC.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
data.dat 90 233 Astrometric data for 233 compact radio sources
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Byte-by-byte Description of file: data.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID *Source Identification designation
9 A1 --- Scode *[* ] Source code
10- 20 A11 --- Alt *Alternate source name
22- 23 I2 h RAh *Right ascension hours (equinox J2000)
25- 26 I2 min RAm *right ascension minutes
28- 34 F7.4 s RAs *right ascension seconds
36- 41 F6.4 s e_RAs *? Error in right ascension
43 A1 --- DE- Sign of declination zone
44- 45 I2 deg DEd *Declination degrees (equinox J2000)
47- 48 I2 arcmin DEm *DEC arc minutes
50- 56 F7.4 arcsec DEs *DEC arc seconds
58- 62 F5.3 arcsec e_DEs *Error in declination
64 I1 --- NCat *? Number of catalogs used for averaging
66- 67 A2 --- ObjClass *[EF?GLQA ] Optical Classification code
69- 73 F5.2 mag V *? Visual magnitude
75 A1 --- u_z [( ] Left parenthesis for uncertain z value
76- 80 F5.3 --- z *? Redshift
81 A1 --- Rparen [) ] Right parenthesis for uncertain z value
83- 86 F4.1 Jy F(5GHz) *? 5-GHz flux density
88 A1 --- ObsCode *[APS] Observation code
90 A1 --- RemCode *[a-g]Remark code
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Note on ID:
Designation according to the IAU convention, which uses the B1950.0
coordinates of right ascension in hours and minutes followed by the sign
and the declination truncated (not rounded) to a tenth of a degree.
Note on Scode:
An asterisk denotes a source south of declination -45deg. having a
preliminary position from a joint CSIRO-JPL program (Jauncey et al.
1982).
Note on Alt:
Names from other catalogs or lists by which a source is commonly known.
Note on RAh, RAm, RAs, DEd, DEm, DEs:
Weighted means of the right ascension and declination at equinox
J2000.0. The weights assigned were inversely proportional to the squares
of the quoted errors in position. Individual catalog positions that were
presented at equinox B1950.0 were precessed to J2000.0 using the
procedure described by Kaplan (1981). Epochs of observation used to
precess the coordinates to J2000.0 were those given in the respective
publications. The epochs, reference equinoxes, and adjustments made to
the right ascension origins of individual catalogs are listed in Table 1
of the source reference.
Note on e_RAs, e_DEs:
Standard errors of the mean positions in right ascension and
declination, taken as the greater of either the internal or external
errors of the standard error of the mean. A right ascension error is not
given for the source 3C 273 (1226+023) because the zero point in right
ascension has been set to the position of 3C 273B reported by Hazard et
al. (1971), which is defined here for J2000.0 as 12h 29m 06s.
Note on NCat:
The number of different catalogs used to obtain the weighted mean.
Note on ObjClass:
A code letter to specify the optical identification of the object,
as follows:
G = galaxy
L = BL Lacertae object
Q = quasar
E =
? = A question mark denotes uncertainty.
Note on V:
The visual magnitude, as taken from any of a variety of sources.
Note on z:
Sources are not given for redshift values. A value is surrounded by
parentheses in bytes 75 and 81 if the z datum is uncertain.
Note on F(5GHz):
As measured with the VLA. It is the flux density of the entire source
and the epoch of measurement is 1979.
Note on ObsCode:
The codes given in the source reference are as follows:
A = source observed by the VLA and JPL
P = primary VLA calibrator
S = secondary VLA calibrator
However, only the A code is present in the published catalog.
Note on RemCode:
A lower case letter for a remark listed following the published table:
a = nebulous extension
b = extended H II
c = optical double
d = optical multiple
e = optically diffuse
f = nebulous (POSS E plate)
g = diffuse (POSS O plate)
Remarks and Modifications:
The candidate sources were selected from a number of astrometric and
survey reference catalogs that are listed in Table 1 of the source
reference. Six sources south of declination -45 deg. were included
from Jauncey et al. (1982). All selected sources display little or
no spatial structure at the arcsecond level Four of the sources
listed in the catalog have subsequently been dropped because they
show unacceptable structure (Kumkova, I. I. 1990, private
communication) and have flat or complex radio spectra. The accuracy
of the radio positions of the catalog sources is <= 0.1 arc seconds,
with the majority <= 0.01". Additional observations are expected to
refine the positions to <= 0.005". It is expected that the machine-
readable version of the catalog will be updated from time to time
as improved positions become available. For additional information
concerning the reasons for the preparation of the catalog, the
selection of candidate radio sources, and the distribution of
sources over the sky, the source reference should be consulted.
References:
Argue, A. N., de Vegt, C., Elsmore, B. Fanselow, J., Harrington, R.,
Hemenway, P., Johnston, K. J., Kuehr, H., Kumkova, I., Niell, A. E.,
Walter, H., & Witzel, A. 1984, A catalog of selected compact radio
sources for the construction of an extragalactic radio/optical reference
frame, Astron. and Astrophy., 130, 191
Hazard, C., Sutton, J., Argue, A. N., Kenworthy, C. M., Morrison,
L. V., & Murray, C. A. 1971, Nature, 233, 89
Jauncey, D. L., Preston, R. A., Niell, A. E., Harvey, B., Meier, D.
L., Moraboto, D. C., Slade, M. A., & Tzjoumis, A. 1982, private
communication cited in source reference
Kaplan, G. H. 1981, United States Naval Obs. Circ. No. 163
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(End) N. G. Roman, C.-H. Lyu, N.P.M. Kuin [Hughes STX/NASA] 4-4-1996