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Astron. Astrophys. 359, 907-931 (2000)

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2. Observations

We chose to observe, for the present study, a number of clusters sharing different properties or locations in the Galaxy, with various masses and structural parameters. In order to detect the tidal extensions around globular clusters, it is necessary to have very wide field observations. During the years 1996 and 1997, optical observations were performed at the ESO Schmidt telescope with photographic films. The field of view is of [FORMULA] with a scale of 67.5"/mm. In combination with the UG1, BG12 and RG630 filters, the Kodak Tech Pan emulsion 4415 provides passbands close to U, B, and R, respectively. Eventually, we use only the R and B filters for this analysis, since the U band images are significantly shallower than the images in the other two filters. The sample of clusters is enlarged by using some ESO and SERC survey plates available at the Centre d'Analyse des Images (CAI) of the Paris Observatory, along with a few POSS I plates kindly provided by Leiden Observatory. All the observed globular clusters studied in this paper are listed in Table 1 with corresponding plates/films identification numbers, filters, and exposure times. All these photographic plates and films are digitized using the MAMA (Machine Automatique à Mesurer pour l'Astronomie) scanning machine at the CAI, which provides a pixel size of 10 µm . The astrometric performances of the machine are described in Berger et al. (1991).


[TABLE]

Table 1. List of observed globular clusters. About plates/films, ESO and SRC stand for the plates of the corresponding two surveys. All the other plates/films are from our observations, except the two plates E131 and E1069 which are from the POSS I.
Notes:
[FORMULA]) Northern GCs are taken on POSS I plates.


Table 2 displays for each cluster, its J2000 equatorial coordinates ([FORMULA],[FORMULA]), its galactic coordinates (l,b), its equatorial rectangular coordinates (X,Y,Z), and, when available, its velocity components (U,V,W) in the equatorial rectangular system.


[TABLE]

Table 2. The X,Y,Z positions are from Harris (1996) and the U,V,W velocities from Dauphole et al. (1996).
Notes:
[FORMULA]) These cluster velocities are from Dinescu et al. (1997).
[FORMULA]) These cluster velocities are from Scholz et al. (1998).


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© European Southern Observatory (ESO) 2000

Online publication: July 13, 2000
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