J/ApJS/242/5 40yr of geodetic/astrometric VLBI obs. of ICRF sources (Xu+, 2019)
Structure effects for 3417 Celestial Reference Frame radio sources.
Xu M.H., Anderson J.M., Heinkelmann R., Lunz S., Schuh H., Wang G.L.
<Astrophys. J. Suppl. Ser., 242, 5 (2019)>
=2019ApJS..242....5X 2019ApJS..242....5X
ADC_Keywords: Interferometry; Radio sources
Keywords: astrometry ; catalogs ; methods: data analysis ; quasars: general ;
reference systems ; techniques: interferometric
Abstract:
Geodetic/astrometric very long baseline interferometry (VLBI) has been
routinely observing using various global networks for 40yr, and it has
produced more than 10 million baseline group delay, phase, and
amplitude observables. These group delay observables are analyzed
worldwide for geodetic and astrometric applications, for instance, to
create the International Celestial Reference Frame (ICRF). The phase
and amplitude observables are used in this paper, by means of closure
analysis, to study intrinsic source structures and their evolution
over time. The closure amplitude rms, CARMS, indicating how far away a
source is from being compact in terms of morphology, is calculated for
each individual source. The overall structure-effect magnitudes for
3417 ICRF radio sources are quantified. CARMS values larger than 0.3
suggest significant source structures and those larger than 0.4
indicate very extended source structures. The 30 most frequently
observed sources, which constitute 40% of current geodetic VLBI
observables, are studied in detail. The quality of ICRF sources for
astrometry is evaluated by examining the CARMS values. It is confirmed
that sources with CARMS values larger than 0.30 can contribute
residual errors of about 15ps to geodetic VLBI data analysis and those
with the CARMS values larger than 0.4 generally can contribute more
than 20ps. We recommend CARMS values as an indicator of the
astrometric quality for the ICRF sources and the continuous monitoring
of the ICRF sources to update CARMS values with new VLBI observations
as they become available.
Description:
We analyzed almost 40yr of dual-frequency, S/X band,
geodetic/astrometric VLBI observations driven by various global
geodetic VLBI observing campaigns (e.g., the NASA Crustal Dynamics
Project (Coates+ 1985ITGRS..23..360C 1985ITGRS..23..360C) and the International Radio
Interferometric Survey program (Carter & Robertson 1986sgg..conf..269C))
since 1979, and coordinated by the International VLBI Service for
Geodesy and Astrometry (IVS; Schuh & Behrend 2012JGeo...61...68S 2012JGeo...61...68S ;
Nothnagel+ 2017JGeod..91..711N 2017JGeod..91..711N ; please also refer to the IVS website)
since its foundation in 1999. Geodetic/astrometric VLBI sessions in
general have a duration of either 24hr or 1hr. The majority of these
24hr sessions are Earth Orientation Parameter (EOP) sessions (twice
per week, R1 and R4), Terrestrial Reference Frame (TRF) sessions (once
every two months), and CRF sessions (at least once every two months).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 88 3417 Closure amplitude rms (CARMS) and
closure phase rms (CPRMS) values
for 3417 ICRF3 sources
--------------------------------------------------------------------------------
See also:
I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)
I/325 : Radio-optical reference frame link (Zacharias+ 2013)
J/AJ/110/880 : Radio reference frame (Johnston+ 1995)
J/ApJS/128/17 : VLBA obs. of radio reference frame sources. III. (Fey+, 2000)
J/A+A/375/661 : Stability of VLBI reference frame (Gontier+, 2001)
J/ApJS/141/13 : VLBA calibrator survey: VCS1 catalog (Beasley+, 2002)
J/AJ/126/2562 : Second VLBA calibrator survey: VCS2 (Fomalont+, 2003)
J/AJ/127/3587 : VLBI ICRF. II (Fey+, 2004)
J/AJ/127/3609 : VLBI observations of southern ICRF sources (Ojha+, 2004)
J/AJ/129/1163 : Third VLBA calibrator survey: VCS3 (Petrov+, 2005)
J/AJ/131/1872 : Fourth VLBA calibrator survey: VCS4 (Petrov+, 2006)
J/AJ/133/1236 : Fifth VLBA calibrator survey: VCS5 (Kovalev+, 2007)
J/AJ/136/580 : Sixth VLBA calibrator survey: VCS6 (Petrov+, 2008)
J/A+A/526/A102 : VLBI obs. of 105 extragalactic radio sources (Bourda+, 2011)
J/A+A/529/A91 : Proper motions of 555 quasars from VLBI (Titov+, 2011)
J/A+A/559/A95 : Fitted proper motions for the DR solution (Titov+, 2013)
J/MNRAS/430/2633 : The epoch ICRF (Xu+, 2013)
J/AJ/150/58 : VLBI ICRF2 (Fey+, 2015)
J/AJ/151/154 : Second epoch VLBA Calibrator Survey (VCS-II) (Gordon+, 2016)
J/AJ/151/79 : Radio fluxes of ICRF2-Gaia transfer sources (Le Bail+, 2016)
http://ivscc.gsfc.nasa.gov/program/master.html/ : The International VLBI
Service (IVS) for Geodesy & Astrometry master files (since 1979)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- IERS IERS designation (HHMM+DDd; B1950)
11- 14 F4.2 --- CARMS-N [0/1.4] CARMS value from natural weighting scheme
17- 20 F4.2 --- CARMS-B [0/1.7] CARMS value from basic-noise
weighting scheme
23- 26 F4.2 --- CARMS-U [0/1.7] CARMS value from uniform weighting scheme
30- 36 I7 --- Namp [0/2909197] Number of closure amplitudes
39- 42 F4.1 deg CPRMS-N [0/94] CPRMS value from natural weighting scheme
45- 48 F4.1 deg CPRMS-B [0/95.2] CPRMS value from basic-noise
weighting scheme
51- 54 F4.1 deg CPRMS-U [0/93] CPRMS value from uniform weighting scheme
59- 64 I6 --- Npha [0/610681] Number of closure phases
71- 74 I4 --- Nses [1/4655] Number of sessions (1)
79- 84 I6 --- Nobs [12/439113] Number of observations (1)
86 A1 --- F-ICRF2 Category flag in ICRF2 catalog (2)
88 A1 --- F-ICRF3 Category flag in ICRF3 catalog (2)
--------------------------------------------------------------------------------
Note (1): Taken from the ICRF3 catalog, see
http://iers.obspm.fr/icrs-pc/newwww/icrf/icrf3sx.txt
Note (2): Category flag as follows:
D = defining source, i.e., define the reference frame axes;
S = special handling source;
O = other source.
--------------------------------------------------------------------------------
History:
Table 2 sent directly by the author for the 3417 sources.
Acknowledgements:
Minghui XU [Huazhong university of sciences & technology; hust.edu.cn]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Dec-2019