C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST00:04:51

2009A&A...506.1477T - Astronomy and Astrophysics, volume 506, 1477-1485 (2009/11-2)

Effect of asymmetry of the radio source distribution on the apparent proper motion kinematic analysis.


Abstract (from CDS):

Information on physical characteristics of astrometric radio sources, such as magnitude and redshift, is of great importance for many astronomical studies. However, data usually used in radio astrometry is often incomplete and outdated. Our purpose is to study the optical characteristics of more than 4000 radio sources observed by the astrometric VLBI technique since 1979. We also studied the effect of the asymmetry in the distribution of the reference radio sources on the correlation matrices between vector spherical harmonics of the first and second degrees. The radio source characteristics were mainly taken from the NASA/IPAC Extragalactic Database (NED). Characteristics of the gravitational lenses were checked with the CfA-Arizona Space Telescope LEns Survey. SIMBAD and HyperLeda databases were also used to clarify the characteristics of some objects. Also we simulated and investigated a list of 4000 radio sources evenly distributed around the celestial sphere. We estimated the correlation matrices between the vector spherical harmonics using the real as well as modelled distribution of the radio sources. A new list OCARS (optical characteristics of astrometric radio sources) of 4261 sources has been compiled. Comparison of our data of optical characteristics with the official International Earth Rotation and Reference Systems Service (IERS) list showed significant discrepancies for about half of the 667 common sources. Finally, we found that asymmetry in the radio source distribution between hemispheres could cause significant correlation between the vector spherical harmonics, especially in the case of sparse distribution of the sources with high redshift. We also identified radio sources having a many-year observation history and lack of redshift. These sources should be urgently observed with large optical telescopes. The list of optical characteristics created in this paper is recommended for use as a supplementary material for the next international celestial reference frame (ICRF) realization. It can be also effectively used for cosmological studies and planning of observing programs both in radio and optical wavelength.

Abstract Copyright:

Journal keyword(s): astrometry - techniques: interferometric - astronomical data bases: miscellaneous - cosmology: miscellaneous

VizieR on-line data: <Available at CDS (J/A+A/506/1477): ocars.dat>

Nomenclature: ocars: [TM2009] BHHMM+DDd N=4261.

Status at CDS:   All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 1

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Number of rows : 1

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 NAME SCP reg ~ ~           ~ 65 0

C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST00:04:51

Available data : Basic data  •  Identifiers  •  Plot & images  •  Bibliography  •  Measurements  •  External archives  •  Notes  •  Annotations

Basic data :
NAME SCP -- Region defined in the sky
Origin of the objects types :

(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases

Other object types:
reg ()
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
ICRS coord. (ep=J2000) :
No Coord.

The link on the acronym of the identifiers give access to the information for this acronym in the dictionary of nomenclature.
Identifiers (2) :
An access of full data is available using the icon Vizier near the identifier of the catalogue

NAME SCP NAME South Celestial Pole

References (65 between 1850 and 2020) (Total 65)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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