J/AJ/139/1713 Celestial Reference Frame at 24 and 43GHz. II (Charlot+, 2010)
The Celestial Reference Frame at 24 and 43 GHz. II. Imaging.
Charlot P., Boboltz D.A., Fey A.L., Fomalont E.B., Geldzahler B.J.,
Gordon D., Jacobs C.S., Lanyi G.E., Ma C., Naudet C.J., Romney J.D.,
Sovers O.J., Zhang L.D.
<Astron. J., 139, 1713-1770 (2010)>
=2010AJ....139.1713C 2010AJ....139.1713C
ADC_Keywords: Fundamental catalog ; Positional data ; VLBI ; QSOs
Keywords: astrometry - quasars: general - radio continuum: galaxies - surveys
Abstract:
We have measured the submilliarcsecond structure of 274 extragalactic
sources at 24 and 43 GHz in order to assess their astrometric
suitability for use in a high-frequency celestial reference frame
(CRF). Ten sessions of observations with the Very Long Baseline Array
have been conducted over the course of ∼5 years, with a total of 1339
images produced for the 274 sources. There are several quantities that
can be used to characterize the impact of intrinsic source structure
on astrometric observations including the source flux density, the
flux density variability, the source structure index, the source
compactness, and the compactness variability.
Description:
We observed a total of 351 extragalactic radio sources using the 10
antennas of the VLBA of the National Radio Astronomy Observatory
(NRAO) over the course of 10 sessions spanning five years from
2002-2007.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 274 Parameters of naturally weighted images at 24GHz
table3.dat 68 132 Parameters of naturally weighted images at 43GHz
table4.dat 27 275 Source structure indices
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See also:
I/251 : VLBI International Celestial Reference Frame (ICRF) (Ma+, 1997)
J/AJ/127/3587 : VLBI ICRF. II (Fey+, 2004)
J/AJ/139/1695 : Celestial Reference Frame at 24 and 43GHz. (Lanyi+, 2010)
Byte-by-byte Description of file: table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- BName Source name based on B1950 position
(HHMM+DDd)
10- 19 A10 "DD-MM-YYYY" ObsDate Observation date
21- 24 F4.2 mas amaj Beam FWHM major axis (1)
26- 29 F4.2 mas bmaj Beam FWHM minor axis (1)
31- 33 I3 deg PA [-90/90] Beam Major axis position angle
(measured north through east) (1)
35- 39 F5.2 Jy/beam Speak Peak flux density (in Jy/beam) (2)
41- 45 F5.2 Jy Stot Total flux density (2) (3)
47- 50 F4.1 mJy/beam Srms root mean square (rms) of the residuals
of the final hybrid image (2)
52- 68 A17 --- CLevels Contour Levels, in mJy/beam (4)
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Note (1): The restoring beam is an elliptical Gaussian.
Note (2): at 24 GHz for table2, and 43 GHz for table3.
Note (3): The total image flux defined by the sum of the CLEAN components. In
some cases, this may be slightly less than the peak flux density due to the
presence of components with negative amplitude in the CLEAN model.
Note (4): Contours levels are represented by the geometric series 1,...,2n,
e.g., for n=5 the contour levels would be ±1, 2, 4, 8, 16, 32.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- BName Source name
10 I1 --- NX ?=- Number of observations in X band (8.5GHz)
12 I1 --- SX.m ?=- Minimum structure index for X band (8.5GHz) (1)
14 I1 --- SX.M ?=- Maximum structure index for X band (8.5GHz) (1)
16- 17 I2 --- NB ?=- Number of observations in B band (24GHz)
19 I1 --- SB.m ?=- Minimum structure index for B band (24GHz) (1)
21 I1 --- SB.M ?=- Maximum structure index for B band (24GHz) (1)
23 I1 --- NQ ?=- Number of observations in Q band (43GHz)
25 I1 --- SQ.m ?=- Minimum structure index for Q band (43GHz) (1)
27 I1 --- SQ.M ?=- Maximum structure index for Q band (43GHz) (1)
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Note (1): The "structure index" is a function of the delay correction τ.
The index is defined from the median delay correction τm calculated
for all projected VLBI baselines that could be possibly observed with
Earth-based VLBI. The index is defined from the delay in picoseconds:
1 = 0ps≤τm<3ps
2 = 3ps≤τm<10ps
3 = 10ps≤τm<30ps
4 = 30ps≤τm<∞
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History:
From electronic version of the journal
30-Jun-2012: Insert into VizieR
29-Mar-2019: Units for Srms corrected for mJy/beam
References:
Lanyi et al., Paper I, 2010AJ....139.1695L 2010AJ....139.1695L, Cat. J/AJ/139/1695
(End) Patricia Vannier [CDS] 21-May-2012