



      A REVISED SHAPLEY-LINDSAY CATALOGUE OF LMC CLUSTERS

               Two Files :  README3.TXT  -  the file you are now reading.
               SL-REV3.TXT  -  revised SL catalogue of LMC star clusters.


    Introduction.
          In the last two centuries numerous attempts have been made to
    catalogue the various interesting objects (star clusters, nebulae and
    variable stars etc) in the LMC. Unfortunately the accuracy and precision
    of published positions has often left much to be desired. Even in the
    1960s, when surveys were probing fainter objects, some positions
    being published were still rather rough, making it difficult to identify
    some objects in the absence of reliable charts.
          The present work has concentrated on a very useful dataset, the
    Shapley-Lindsay (SL) catalogue of 898 LMC star clusters in order to:
     facilitate identification by presenting positions of higher precision
     ensure that each SL position corresponds closely to an intended object
     produce a dataset which can be further manipulated electronically, if
      required eg to be ported to popular planetarium-type programs
     ensure that all SL objects are included, such as those which have been
      omitted from the Hodge-Wright (HW) atlas of the LMC (1967), and the
      omitted clusters in the LMC Bar (KMHK catalogue,1990).

    The Shapley-Lindsay Catalogue.
          This compilation of 898 LMC clusters was published by H. Shapley
    and E.M. Lindsay (1963), based on searches of ADH Schmidt plates. Their
    catalogue covers the whole range of morphologies, from the large bright
    aggregations now known as stellar associations, through the dense swarms
    of stars we recognize as globular clusters,  to the smaller gatherings
    which are the counterparts of our galactic clusters (open clusters). The
    listed objects generally lie between  RA 4h24m and 6h34m, and Dec. -63
    and -75. The two main problems with the original SL catalogue, as I see
    it, are :
     positions which are approximate, and subject to both systematic and
    random errors. These problems are alluded to in the HW Atlas (p15, p37),
    and I concur. Right Ascensions are frequently out by 10 or 20s, and
    declinations are out by 4-5', or 10', which helps  explain why HW could
    not find particular SL clusters, and were led to misidentify others.
     difficulty in distinguishing between small clusters and background
    galaxies, especially in the outer reaches of the LMC. Clearly, this was
    a limitation of their plate material. Images from the large Schmidt
    telescopes (via the Digitized Sky Survey) make it easy to distinguish
    the two.
       While the SL catalogue gave diameters for all objects, I found that
    very small values (5-10 arcsec) would just as likely indicate a galaxy
    as a cluster.
    Catalogues consulted in preparation of "SL-Revised".
    1. "A Catalog of LMC Star Clusters outside the Hodge-Wright Atlas",
       Olszewski, Edward W., Harris, Hugh C., Schommer, Robert A. and
       Canterna, Ronald W. 1988, Astron. J. 95,84-90.  [OHSC]
    2. "The Cluster system of the Large Magellanic Cloud", Kontizas,M.,
       Morgan,D., Hatzidimitriou,D. and Kontizas, E. 1990, Astron. Astrophys.
       Suppl. 84, 527-547.       [KMHK].
    3. "Revised and extended catalog of Magellanic system clusters, 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
    4. The Guide Star Catalog, v1.1, Space Telescope Science Institute
       1989.                    [GSC]
    5. 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 have proved adequate for the purposes of
    ascertaining correct positions, there are several on-line catalogues
    which cover the LMC - 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 Plan.
        The BSDL catalogue, being very extensive (6659 LMC obj.), was deemed
    to include most, if not all, SL objects, while providing semi-precise
    positions, dimensions and alternative designations. The BSDO data was
    selected as a suitable starting point. All SL objects were extracted
    from the BSDL catalogue, and ported to a spreadsheet file for further
    editing. Each SL object was then located in the KMHK catalogue, and the
    position was corrected for precession (1950 --> 2000) and compared with
    the BICA catalogue. [The KMHK catalogue couldn't identify all SL objects
    with certainty.] If KMHK and BSDO were in good agreement, the former was
    accepted. In cases of disagreement, ie when the RA differed by more than
    4s, and/or declination by more than 10", the object was set aside for
    further examination. In cases of very severe disagreement it was found
    prudent to download the field from the Digitized Sky Survey (DSS). About
    90 problem objects were inspected on DSS images. Not every SL object
    required a DSS image (and time did not allow), as it was assumed that if
    KMHK and BSDO positions agreed, then the identification was secure.
    Furthermore, if a check of the GSC revealed a non-stellar object at the
    same spot, then the identification was hardly in doubt. The original SL
    coordinates were also frequently referred to, as about 10% of SL objects
    are missing in the KMHK catalogue.
          To rely only on the HW Atlas for identifications was found to be a
    little hazardous, as misidentifications are far too common, and it seems
    that the compilers of the KMHK and BSDO catalogues have been led astray,
    in a few instances, by the HW charts. Particularly where the faintest
    SL clusters are concerned, which are barely visible. A notable instance
    is SL 834. The original SL position is actually quite close to the mark,
    but the HW chart erroneously marks a spot 30' due S, where nothing can
    be seen.  The KMHK and BSDO cataloguers, obviously guided by the HW
    position, reported the positions of two different asterisms in the near
    vicinity.

    The Catalogue (SL-REV.TXT):
    899 records + notes.

    Field Name           Description
    =========================================================================
    SL          : Ordinal number from SL catalogue.
    Type        : Classification of object.   Key :
                  C = Open cluster     GC = Globular cluster (Suntzeff 1992)
                  GC*  Red GC as called by Hodge (1960),  now rejected. 
                  YPC = Young Populous Cluster ("blue globular", Hodge 1961)
                  GAL = Galaxy     ASS = Stellar Association
                  AST = Asterism  N = Nebula   ND = Not Detected
    NGC, IC etc : Corresponding number in NGC and IC catalogues.
    GSC number  : GSC object attributable to the SL object.
                  * GSC no. included where searched for and found.
                  * N/A means that GSC was searched, but no attributable GSC
                  object was found.
                  * Blank means no GSC search has been done for that object
                  (and chances are the SL cluster is too faint for the GSC).
    [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.]
    GSC Mag.    : Average GSC mag., from GSC Catalog. For reference only.
    RA (2000)   : Right Ascension, equinox J2000.
    Dec (2000)  : Declination, equinox J2000.
    Size-Arcmin : Dimensions of cluster, (N-S and E-W), in arcmins.

    Bibliography:
    Hodge, P.W. 1960. Studies of the Large Magellanic Cloud, I. The red
                  globular clusters. Astrophys. J., 131, 351-357.
    Hodge, P.W. 1961. Studies of the Large Magellanic Cloud, V. The young
                  populous clusters. Astrophys. J., 133, 413-419.
    Shapley, H. and Lindsay, E.M. 1963. A catalogue of clusters in the Large
                  Magellanic Cloud. Irish Astron. Journal 6, 74.
    Suntzeff, Nicholas B. 1992. "Population II in the Milky Way and the LMC"
                  in Barbuy and Renzini (eds) (The Stellar Populations of
                  Galaxies, IAU Symposium 149), (Kluwer, Dordrecht) pp23-28.

    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.

    Compiled by M. Morel, 2001 June 13.
    morel@ozemail.com.au
    http://www.ozemail.com.au/~morel










































































































































































































