THE ASTRONOMICAL JOURNAL    VOLUME 114, NUMBER 1, PAGE 198          JULY 1997

                PROPERTIES OF THE MONOCEROS R2 STELLAR CLUSTER

                               JOHN M. CARPENTER

                 Institute for Astronomy, 2680 Woodlawn Drive,
                 University of Hawaii, Honolulu, Hawaii 96822
                 Electronic mail: carp@galileo.ifa.hawaii.edu

                               MICHAEL R. MEYER

              Max-Planck-Institut fur Astronomie, Konigstuhl 17,
                          Heidelberg, Germany D-69117
                     Electronic mail: meyer@mpia-hd.mpg.de

                              CATHERINE DOUGADOS

            Laboratoire d'Astrophysique, Universite Joseph Fourier,
                    B.P. 53X, 38041 Grenoble Cedex, France
                  Electronic mail: dougados@gag.observ-gr.fr

                               STEPHEN E. STROM

       Department of Physics and Astronomy, University of Massachusetts,
                         Amherst, Massachusetts 01003
                Electronic mail: sstrom@donald.phast.umass.edu

                             LYNNE A. HILLENBRAND

 Department of Astronomy, University of California, Berkeley, California 94720
                  Electronic mail: lynne@astraea.berkeley.edu

                                   ABSTRACT

     We present an extensive study of the stellar population of an embedded
     cluster in the MonR2 molecular cloud based upon a wide field (~15' x
     15') J, H, and K band mosaic, deep near-infrared imaging at J, H, K,
     and nbL' bands of the central cluster region, and spectroscopic
     observations of 34 stars. By comparing the properties of the MonR2
     cluster with other star forming regions, we ultimately hope to learn
     how the properties and formation of stars of various masses are
     related to the local physical conditions. The K band star counts
     indicate that the MonR2 cluster extends over a ~1.1 pc x 2.1 pc area
     with a FWHM cluster size of ~0.38 pc. Within this region the cluster
     contains ~309 stars brighter than m_K = 14.5m and >~ 475 stars over
     all magnitudes with a central stellar volume density of ~9000 stars
     pc^{-3}. We have further explored the properties of the cluster by
     using the spectroscopic and photometric data to construct an
     extinction-limited sample of 115 stars in the central 0.77 pc x 0.77
     pc region of the cluster that is designed to contain all stars with
     A_V <= 11.3m and stellar masses >= 0.1 Msun. As a lower limit, 62% of
     the stars in this sample contain a near-infrared excess at K and/or L
     band. The K band excess fraction may be as high as 72% if the
     accretion characteristics of the stars in the MonR2 cluster are
     similar to stars in Taurus-Auriga. An initial reconnaissance of the
     stellar mass function suggests that the ratio of high to low mass
     stars in the extinction-limited sample is consistent with the value
     expected for a Miller-Scalo IMF. We do not find compelling evidence
     for mass segregation in the extinction-limited sample for stellar
     masses <~ 2 Msun, although the most massive star (~10 Msun) in the
     cluster appears to be forming near the cluster center. The properties
     of the MonR2 cluster are similar to other rich young clusters in the
     solar neighborhood, such as NGC 2024 and the Trapezium. (c) 1997
     American Astronomical Society.