7 Conclusion

The Master Catalogue of stars towards the Magellanic Clouds (MC2) is now available on the web at CDS. It is a compilation of cross-identified surveys, from optical to IR. The MC2 roughly covers the following area: $4^{\rm h}$ to $7^{\rm h}$ in Right Ascension, and $-61^{\circ}$ to $-78^{\circ}$ in Declination, with slight variations according to the catalogue considered.

We are currently working on the cross-identification of analogous catalogues in the direction of the Small Magellanic Cloud and we plan to add catalogues and tables at other wavelengths: ROSAT, IRAS, and many more specific catalogues, as well the variability informations coming either from MACHO, EROS, OGLE to the second version of the catalogue.

A typical query of the MC2 returns several lines of data. An example is given in Table 3. Each line of data contains the name of the source for all the original catalogues, followed by the magnitudes and the proper motion when the UCAC1 is present. For each catalogue, the distance of the cross-identification is given, except for 2MASS which is taken as reference. The distance associated to a DCMC source is the distance to the 2MASS counterpart. The distance associated to a GSC2.2 source is the distance to the 2MASS counterpart, or the DCMC counterpart when there is no 2MASS counterpart. The distance associated to a UCAC1 source is the distance to the MC2 counterpart (2MASS, DCMC or GSC2.2, depending on the detection bands). At the beginning of each line, RA and Dec are given. The choice of the coordinates has been as follows: when possible, we kept the 2MASS coordinates as the reference, otherwise we took the GSC2.2, then the UCAC1 and finally the DCMC ones.

Figure 14: CMD resulting from the cross-matching between the DCMC (I), 2MASS ($K_{\rm s}$) and GSC2.2 ( $V_{\rm gsc2}$) catalogues. This plot contains 393 179 entries.

We decided to keep the distances of the cross-identifications in the MC2 to give the user the opportunity to judge the reliability of each cross-identification. We have also shown that for some DCMC point sources, this distance was not reliable. But since links for each source allow to access the complete data from the original catalogues through the VizieR search engine (Ochsenbein et al. 2000), it is always possible to retrieve the strip number of the DCMC source and then go to the MC2 web site to find the shifts associated to this strip. Those links are also very valuable in order to retrieve observational data such as image or scan number, flags or whatever parameter the user would like to know from the original catalogues.

This reference catalogue is made available as a support for a number of studies concerning, e.g. the stellar populations in the Magellanic Clouds, the structure of the Clouds, or certain classes of objects (Cepheids, AGB stars, etc.). Recent articles, such as those by Zaritsky et al. (2002), van der Marel (2001), Nikolaev & Weinberg (2001) and Cioni et al. (2000b) have demonstrated the power of optical and near-infrared surveys to improve our understanding on these neighbouring galaxies.

Figure 15: CMD, colour-colour diagrams and spatial distribution of the blue stars selected with (V- $K_{\rm s}) \leq 1$ in the (I, V-$K_{\rm s}$) diagram. There are 19 646 sources on each panel. The I band is from DENIS and the J, H and $K_{\rm s}$ are from 2MASS. The contour levels have been added so as to show the locus of different types of objects.

 

 

Table 3: Subsample of the MC2. Each line of data corresponds to one point source.

RA	Dec	2MASS	J	dJ	H	dH	$K_{\rm s}$	d$K_{\rm s}$
93.769831	-75.633698	0615047-753801	12.380	0.022	12.177	0.024	12.076	0.029
93.760565	-75.632538	0615025-753757	16.072	0.089	15.975	0.178	15.273	null
93.769231	-75.629761	0615046-753747	16.413	0.123	16.141	0.211	15.611	0.261
93.756995	-75.621536	0615016-753717	16.192	0.098	15.352	0.106	15.443	0.215
DCMC	I	dJ	J	dJ	$K_{\rm s}$	d$K_{\rm s}$	dist
061504.60-753800.7	12.999	0.006	15.788	0.188	99.000	99.000	0.853030
061502.40-753757.5	16.501	0.062	15.866	0.230	99.000	99.000	0.621811
..	...	...	...	...	...	...	...
..	...	...	...	...	...	...	...
GSC2.2	F	dF	J	dJ	V	dV	dist
S1102121266	13.24	$\pm$0.23	13.95	$\pm$0.17	--	$\pm$	0.192289
S11021214338	17.40	$\pm$0.23	17.90	$\pm$0.18	--	$\pm$	0.203876
S11021214339	17.44	$\pm$0.23	18.29	$\pm$0.18	--	$\pm$	0.554134
S11021214495	18.30	$\pm$0.24	--	$\pm$	--	$\pm$	0.251949
UCAC1	mag	PMra	PMdec	dist
00697288	13.22	+27.3	-9.7	0.045439
...	...	...	...	...
...	...	...	...	...
...	...	...	...	...

Acknowledgements

We thank an anonymous referee for very constructive suggestions which helped to improve the present paper. We would like to thank François Ochsenbein for his help with the catalogues. This research has made use of the SIMBAD astronomical database, the VizieR catalogue service, and the ALADIN interactive sky atlas, all operated at CDS, Strasbourg, France. This work has been partly supported by the ASTROVIRTEL Project which is run by the ESO/ST-ECF Archive and funded by the European Commission under contract HPRI-CT-1999-00081. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation, and from DENIS, which is the result of a joint effort involving human and financial contributions of several Institutes mostly located in Europe. It has been supported financially mainly by the French Institut National des Sciences de l'Univers, CNRS, and French Education Ministry, the European Southern Observatory, the State of Baden-Württemberg, and the European Commission under a network of the Human Capital and Mobility program. The Guide Star Catalogue-II is a joint project of the Space Telescope Science Institute and the Osservatorio Astronomico di Torino. Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, for the National Aeronautics and Space Administration under contract NAS5-26555. The participation of the Osservatorio Astronomico di Torino is supported by the Italian Council for Research in Astronomy. Additional support is provided by European Southern Observatory, Space Telescope European Coordinating Facility, the International GEMINI project and the European Space Agency Astrophysics Division.