
                       A COMPILED CATALOGUE OF SMC STAR CLUSTERS

               Two Files :  READSMC.TXT  -  the file you are now reading.
               SMC_CLUS.TXT  -  compiled catalogue of SMC star clusters.
                  220  objects.  J2000 positions and identifications.

    Introduction.
            As a follow-up to my reworking of the Shapley-Lindsay  (SL)
    catalogue of LMC star clusters, a similar plan of attack has been used
    for the star clusters of the SMC. The number of catalogued objects here
    is only a fraction of that in the LMC, so it was fairly straightforward
    to work through all 220 clusters identified by Hodge & Wright (1977) in
    their atlas of the SMC.
    Lindsay Catalogue of SMC clusters.
            Four catalogues of SMC clusters were used by Hodge and Wright
    in compiling their SMC atlas, with Eric Lindsay's 1958 catalogue
    being the longest, with 116 entries. I have given Lindsay's compilation
    priority status, and kept his clusters in correct numerical order, even
    though the precise J2000 positions are not always strictly in order
    of increasing RA. Entries from other catalogues (K, WG and HW) are
    inserted in the most appropriate positions, according to RA. Compared to
    the LMC, identification problems were rare, and the Hodge-Wright atlas
    was found to be very reliable, displaying the positions of clusters with
    commendable accuracy. Nevertheless, Lindsay's published catalogue was
    consulted to be sure no vital information was missed. Curiously, while
    the Lindsay catalogue gives diameters in arcmin for each cluster, the
    values given are generally far too large, up to 79 arcmin. It is clear
    that some other scale is meant, perhaps an absolute diameter in parsecs?
    The BSDL diameter data has been inserted instead.
    Positional Data.
            Douglas Welch (1991) published a list of astrometric positions
    for 203 SMC clusters, omitting 17 objects which could not be measured
    for various reasons. After extensive checking against other catalogues
    his data have been accepted in their entirety.
            All clusters have been searched for in the GSC, via Guide7. Some
    clusters not in the GSC were found in the USNO-A2.0, while a few
    had to be estimated by reference to nearby USNO-A2.0 stars.

    MACHINE-READABLE CATALOGUES USED.
    General identifications; diameters.
    1."Revised and extended catalog of Magellanic system clust, associations
       and emission nebulae", II. Bica, E.L.D., Schmitt, H.R., Dutra, C.M.
       and Oliveira, H.L. Astron. J. 117, 238-246 (1999).         [BSDO]
       See also http://www.if.ufrgs.br/~dutra/catpage.html
    Astrometric Data.
    2. The Guide Star Catalog, v1.1, Space Telescope Science Institute
       1989.                    [GSC]
    3. USNO-A2.0 Catalog, Monet, D., Bird, A., Canzian, B. et al 1998,
       US Naval Observatory, Washington DC.   [USNO-A2.0]
       See also http://www.usno.navy.mil/pmm

            While the above catalogues proved adequate for the purposes of
    ascertaining correct positions, there are several on-line catalogues
    which cover the SMC - 2MASS, DENIS and MACS. The first two in particular
    can be accessed using the Vizier utility at CDS, Strasbourg. Homepage is
    http://cdsweb.u-strasbg.fr/CDS.html, and follow the links.

    THE CATALOGUE (SMC_CLUS.TXT):
    221 records + notes.
    The catalogue is divided into two parts - A and B. The clusters from the
    lists of Kron (1956), Lindsay (1958) and Westerlund/Glaspey (1971) are
    grouped together in Part A, while the 86 small and faint clusters listed
    by Hodge and Wright (1974) are in Part B. The format is essentially the
    same for both parts, as follows:

    Col./Field Name           Description
    =========================================================================
    1  LIN      : Ordinal number from Lindsay cat. (Part A)
       HW       : Ordinal number from HW catalogue (Part B).
    2  Class    : Classification of object.   Key :
                  C = Open cluster     GC = Globular cluster
                  C-g = cluster with superficial resemblance to a GC (often
                  listed as GC elsewhere).
                  ND = Not detected.
    [Note: Lin. 10 = NGC 121 is said to be the only Pop. II GC in SMC.]
    3  Id.2     : Alternative identifiers (Kron or Westerlund/Glaspey nos.)
    4  Id.3     : Corresponding number in NGC and IC catalogues.
    5  GSC      : GSC object attributable to the cluster.
                  * N/A means that GSC was searched, but no attributable GSC
                  object was found.
    [The majority of GSC objects found are classed as "non-stellar". From
    time to time an individual cluster star is entered, provided it is close
    to the adopted centre of the cluster.]
    6  GSC Mag. : Average GSC mag., from GSC Catalog. For reference only.
    7  RA (2000): Right Ascension, equinox J2000.
    8  Dec(2000): Declination, equinox J2000.
    9           : Source of position :  DW = D.L. Welch (1991)
                  G = GSC 1.1   A = USNO-A2.0  E = Estimated
    10,11 Size  : Dimensions of cluster, (N-S and E-W), in arcmins.
                  Sources : BSDL for Part A clusters.
                          : Hodge & Wright (1974) for Part B clusters.
                  Note that the BSDL compilation lists diameters for the HW
                  clusters which appear overlarge by a factor of almost 10
                  in some cases. I have copied the original HW diameters,
                  which seem more realistic.

    Bibliography:
    Hodge, P.W. and Wright, F.W. 1977. The Small Magellanic Cloud.
                  University of Washington Press, Seattle.  [HW]
    Ibid.         1974. Astron. J. 79,858.
    Lindsay, E.M. 1958, Mon. Not. R. ast. Soc. 118,172  [LIN]
    Kron, G.E. 1956, Publ. Astron. Soc. of Pacific, 68, 125  [K].
    Welch, D. L. 1991, Astron. J. 101, 538-540.
    Westerlund, B.E. and Glaspey, J. 1971, Astron. Astrophys. 10,1  [WG]

    Acknowledgements:
    I wish to acknowledge the valuable assistance of Dave Monet, US Naval
    Observatory, Flagstaff, AZ, in providing the USNO-A2.0 catalogue  on
    CD-ROM.  The work done by Jenni Kay, Lobethal, South Australia, was also
    valuable in checking the correct identifications of clusters. Also, Dr.
    Harold G. Corwin Jr, Brian Skiff and Brent Archinal for help and advice
    in this overall project to compile better positions for MC clusters.

    Compiled by M. Morel, 2001 August 1.
    morel@ozemail.com.au
    http://www.ozemail.com.au/~morel


