A Radio-Optical Reference Frame.VIII.CCD Observations from KPNO and CTIO: Internal Calibration and First Results

Zacharias, N.; Vegt, C. de; Winter, Lars; Johnston, K. J.

doi:10.1086/117750

Cited by 17 publications

(10 citation statements)

References 5 publications

(9 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Kovalewsky et al 1997), it has great potential because of the large number of well-distributed link sources involved (see e.g. Zacharias et al 1995. Within this same context, the identification of of new radio/optical frame link objects is of particular importance (see e.g.…”

Section: Discussionmentioning

confidence: 99%

CCD astrometry of faint compact extragalactic radio sources. III.

Costa¹

2002

A&A

View full text Add to dashboard Cite

Abstract. Optical positions relative to the Hipparcos Catalogue (ESA 1997) have been obtained for the optical counterparts of 38 faint (B ∼ 20−24) southern compact extragalactic radio sources (CERS). Many of these sources are not detectable -or their coordinates not adequately measurable -by means of direct photography with a widefield telescope, so the positions were determined using a multi-step procedure involving CCD and photographic observations. This method responds both to the requirement of attaining small positional errors, and the need to refer the positions to a standard astrometric system. Estimated precisions as good as 50 mas were achieved. For 16 of the above objects we are proposing a completely new optical identification or providing a revised finder. A comparison of our optical positions with available VLBI radio positions is presented. The residuals obtained are in most cases consistent with the precision of our optical data, and provide an evaluation of these CERS as radio/optical frame link sources (or their identification as astrophysically interesting astrometric outliers). Twenty nine of the CERS observed are either defining or candidate fiducial objects of the present International Celestial Reference System (ICRS, Ma et al. 1998), so the optical data we have obtained for them is potentially useful to help mantain and possibly improve the current link of the Hipparcos reference frame to the ICRS.

show abstract

Section: Discussionmentioning

confidence: 99%

CCD astrometry of faint compact extragalactic radio sources. III.

Costa¹

2002

A&A

View full text Add to dashboard Cite

show abstract

“…Kovalewsky et al 1997), on account of the large number of well distributed link sources involved it has a great potential (see e.g. Zacharias et al 1995).…”

Section: Discussionmentioning

confidence: 99%

CCD astrometry of faint compact extragalactic radio sources. II.

Costa

2001

A&A

View full text Add to dashboard Cite

Abstract. Optical positions relative to the Hipparcos Catalogue (ESA 1997) have been obtained for the optical counterparts of 28 faint (B ∼ 20−23) southern compact extragalactic radio sources (CERS). Most of these sources are not adequately observable (or simply not visible) by means of direct photography with a conventional widefield telescope, so the positions were determined using a multi-step procedure involving CCD and photographic observations. This method responds both to the need of attaining small positional errors and the need to refer the positions to a standard astrometric system. Estimated precisions as good as 60 mas were achieved. For 13 of the above objects, namely 0214−522, 0614−349, 0700−465, 0823−500, 1120−274, 1143−331, 1347−218, 1349+027, 1817−254, 1829−718, 1920−211, 2139+028 and 2211−388, we are proposing a new optical identification. A comparison with VLBI radio positions available for these sources is presented. The residuals obtained are in most cases consistent with the precision of our optical data, and provide an evaluation of these faint objects as possible radio/optical frame link sources (or their identification as astrophysically interesting astrometric outliers). Fifteen of the CERS observed are either defining or candidate fiducial objects of the present realization of the International Celestial Reference System (ICRS, Ma et al. 1998), so the optical data we have obtained for them is potentially useful to help mantain and possibly improve the current link of the Hipparcos reference frame to the ICRS.

show abstract

“…In pilot investigations for each run, the approximate optical distortion (third-order term and its zero-point location on the CCD chip) was determined using only the (x, y)-coordinates of well-exposed, stellar images of center-incorner overlap frames (see also Zacharias et al 1995). The resulting parameters are also listed in Table 1.…”

Section: Ccd Framesmentioning

confidence: 99%

“…Candidates have been selected from the list of about 600 extragalactic radio reference frame sources . In a pilot investigation (Zacharias et al 1995) we published results for 16 sources, then based on the FK5 system. Later this project contributed with a subset of about 100 sources to the Hipparcos link (Kovalevsky et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Accurate Optical Positions of Extragalactic Radio Reference Frame Sources

Zacharias

Hall

et al. 1999

The Astronomical Journal

Self Cite

View full text Add to dashboard Cite

Optical positions on the 50 mas level in the Hipparcos system have been obtained for 327 extragalactic, radio reference frame sources for both hemispheres from a 2-step procedure. Positions of secondary reference stars in the 10 ¹ V ¹ 14 magnitude range were obtained from photographic plates taken at the Hamburg astrograph (Northern Hemisphere) and the US Naval Observatory astrograph at Black Birch (Southern Hemisphere) using Hipparcos stars for astrometric plate solutions. Positions of the optical counterparts of compact, extragalactic, radio reference frame sources were then obtained from CCD direct imaging at the KPNO and CTIO 0.9 m telescopes, using the secondary reference star positions and correcting for Ðeld distortions. Several previously unknown counterparts could be identiÐed, and several previously suspected identiÐcations turned out to be empty Ðelds. CCD images are available on the World Wide Web to serve as Ðnding charts. A comparison between the optical and radio positions reveals systematic o †sets of 10 to 40 mas per coordinate as a function of the observing run. Corrections for Galactic rotation and solar motion have been attempted because of a lack of individual proper motions for the secondary reference stars. Neither 0.9 m telescope is an astrometric instrument, and limitations are clearly seen in remaining systematic errors. Orientation angles between the radio system and our optical data are zero within an accuracy of 4 mas (standard error). A signiÐcant reduction of the systematic errors will be achieved with new wide-Ðeld CCD imaging currently been taken in parallel to new 0.9 m observations, to provide more secondary reference star positions with higher precision at a common epoch, which will allow extended modeling of the mapping properties of 0.9 m observations.

show abstract

A Radio-Optical Reference Frame.VIII.CCD Observations from KPNO and CTIO: Internal Calibration and First Results

Cited by 17 publications

References 5 publications

CCD astrometry of faint compact extragalactic radio sources. III.

CCD astrometry of faint compact extragalactic radio sources. III.

CCD astrometry of faint compact extragalactic radio sources. II.

Accurate Optical Positions of Extragalactic Radio Reference Frame Sources

Contact Info

Product

Resources

About