J/MNRAS/430/2797ivo://CDS.VizieR/J/MNRAS/430/2797doi:10.26093/cds/vizier.74302797CDSAssafin M.Vieira-Martins R.Andrei A.H.Camargo J.I.B.,Da Silva Neto D.N.2024-07-21T20:14:12Z2014-06-05T13:30:29ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsurveysastrometryoptical-observationcatalogsWe obtained improved optical positions for 300 ICRF2 sources - the Rio survey. We compared the Rio survey with 10 other selected optical astrometric surveys and studied the link between the Hipparcos Catalogue Reference Frame (HCRF) and the International Celestial Reference Frame, Second Realization (ICRF2). We investigated the possible causes for the observed non-coincidence between the optical and ICRF2 positions. The Rio survey positions were referred to the second version of the United States Naval Observatory CCD Astrograph Catalog (UCAC2), currently the best tested HCRF densification. The sources are between -90{deg}<{delta}<+30{deg}. We used two telescopes with suitable diameters and focal lengths to properly link the observed ICRF2 sources with the UCAC2, using intermediate brightness stars. We certified the astrometry done with many statistical tests. The average 'optical minus ICRF2' offsets and respective standard deviations in ({alpha}, {delta}) were -3mas (41mas) and +4 (45mas). The Rio survey represents well the zero-point offset of the other surveys. The standard error of 3.5mas found for the HCRF/ICRF2 link indicates an error excess that can be originated by a non-coincidence between the observed optical/VLBI positions. We thus discussed the influence of the errors from the UCAC2. Then, we searched for correlations with the source morphology, represented by structure indices defined in the radio and in the optical domain. Finally, we studied how the position offsets could originate from the perturbation of the optical point spread function (PSF) of the source's core, by a second source of flux. We found an analytical relation that describes the resulting centroid shift, as a function of the atmospheric seeing, the brightness ratio and the relative distance between the two contributing flux sources. Two scenarios, modelled by this relation, are discussed: an extinction window in the dust torus nearby the core, and a Galactic star near the line of sight.2013MNRAS.430.2797Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/430/2797CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)J/AJ/127/3587 : VLBI ICRF. II (Fey+, 2004)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/430/2797https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/430/2797http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/430/2797https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/430/2797https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/430/2797http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/430/2797GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/430/2797/table2 (The 300 ICRF2 sources of the Rio survey)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/430/2797/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/430/2797/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/430/2797/table2?GETtext/xml+votable180.050000true1.148574722-47.6054536110.0055555555555555566/60 307 421 532 579 593 700 4436 4448 4696 4770 5154 8199 8299 8345 8487 8615 8717 8915 12301 12352 12475 12580 12599 16962 17019 17110 17215 17351 17516 17529 17541 17579 17734 17791 17857 17909 18002 18022 18035 18037 18271 18378 18457 18506 18624 18661 18669 18718 18755 18871 18907 19101 19190 19271 19370 19398 19523 19567 19609 19629 19831 19872 20099 20503 20657 21012 21049 21117 21121 21266 21358 21437 21564 21758 21768 21924 21935 21960 21968 21972 22363 22396 22501 22658-22659 22917 22950 22965 23014 23022 23099 23127 23323 23335 23383 23761 23882 24116 24123 24608 24809 24845 25083 25255-25256 25302 25428 25493 25503 25630 25742 25864 26000 26083 26100 26115 26131 26292 26301 26303 26363 26550 26966 26983 27060 27220 27310 27423 27466 27909 27926 28208 28453-28454 29016 29218 29384 29570 29675 29714 29795 31176 31190 31211 31334 31391 31430 31529 31535 31559 31664 31857 31894 32311 32325 32841 32948 32961 33048 33549 33560 33684 33825 33827 33829 33973 34013 34038 34099 34123 34210 34264 34330 34428 34461 34517 34571-34572 34675 34699 34870-34871 34931 35079 35370 35440 35651 35786 35801 36155 36188 36417 36554 36785 36877 36941 37064 37217 37385 37474 37480 37819 37919 37994 38189 38277 38383 38416 38474 38579 38734 38763 39489 39557 39577 39848 40060 40344 40479 40527 40692 40730 40990 41059 41072 41088 41275 41310 41511 41578 42060 42571 42853 42883 42901 43257 43366 43399 43417 43566 43694 43822 43936 44034 44043 44147 44247 44502 44614 44658 44661 44776 44805 44832 44899 44908 45162 45178 45196 45393 45409 45446 45614 45621 45763 45774 45795 46055 46251 46310 46337 46373 46394 46459 46588 46762 46764 46851 46964 47014 47016 47080 47106 47268 47375 47534 47540 47941 48023 48123 48228 48362 48589 48595 48610 48798 48846 48965https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/430/2797?format=asciiOpticaldefaultJ/MNRAS/430/2797/table2The 300 ICRF2 sources of the Rio surveyrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIERSIERS name (HHMM+DDd, B1950)meta.id;meta.maincharRAJ2000Right ascension (ICRS), at Epochpos.eq.ra;meta.maine_RAJ2000Mean error along RA from (RA,DE) reductionmasstat.error;pos.eq.raintDEJ2000Declination (ICRS), at Epochpos.eq.dec;meta.maine_DEJ2000Mean error along DE from (RA,DE) reductionmasstat.error;pos.eq.decintVmagV magnitudemagphot.mag;em.opt.VfloatEpoch[1993/2009] Mean epoch of the positionyrtime.epochdoublesigX[3/193] photocentre measuring error along X associated to (RA, DE)masstat.error;pos;instr.detintsigY[3/240] photocentre measuring error along Y associated to (RA, DE)masstat.error;pos;instr.detintNref[5/148] Number of reference starsmeta.numberintdRAOptical minus ICRF position offset in RAcosDEmaspos.eq.ra;arith.diffintdDEOptical minus ICRF position offset in Decmaspos.eq.dec;arith.diffintsRA[0/161] Standard deviation of the contributing individual CCD positions along RA (1)masstat.errorintsDE[0/179] Standard deviation of the contributing individual CCD positions along DE (1)masstat.errorintNo[1/40] Number of contributing individual positionsmeta.numberintX? Structure index in X-band (~8.3GHz) (2)src.morph.paramfloatnullableS? Structure index in S-band (~2.3GHz) (2)src.morph.paramfloatnullableP? P=sqrt(K^2^+R^2^+N^2^) index (3)stat.fit.paramfloatnullableK? Skewness (K index) (3)stat.fit.paramfloatnullableR? Roundness (R index) (3)stat.fit.paramfloatnullableN? Normalness (N index) (3)stat.fit.paramfloatnullableTelTelescope sizeminstr.telfloatSimbadSimbad column added by the CDSmeta.ref.urlchar