THE ASTRONOMICAL JOURNAL    VOLUME 113, NUMBER 1, PAGE 264     JANUARY 1997

          REDDENINGS, METALLICITIES, AND POSSIBLE ABUNDANCE ANOMALIES
                          IN YOUNG GLOBULAR CLUSTERS

                                ATA SARAJEDINI

   Kitt Peak National Observatory, National Optical Astronomy Observatories,
                     P.O. Box 26732, Tucson, Arizona 85726

                                 ANDREW LAYDEN

               Department of Astronomy, University of Michigan,
                        Ann Arbor, Michigan 48109-1090

    We present new photometry in the VI passbands for the ``young''
    globular clusters Rup 106, Ter 7, and Arp 2. After formulating the
    simultaneous reddening and metallicity (SRM) method of Sarajedini [AJ,
    107, 618 (1994)] in the BV passbands, we apply it, along with the SRM
    method in VI, to the red giant branches (RGBs) of these clusters using
    B-V photometry from the literature and the V-I data presented
    herein. We find [Fe/H]=-1.90+/-0.10, E(B-V)=0.18+/-0.02 for Rup 106,
    [Fe/H]=-0.82+/-0.15, E(B-V)=0.07+/-0.03 for Ter 7, and
    [Fe/H]=-1.84+/-0.09, E(B-V)=0.10+/-0.02 for Arp 2. Furthermore, in
    light of this new abundance for Ter 7 and recent work on the luminosity
    of the red horizontal branch, we rederive the age of Ter 7 finding it
    to be some 6 Gyr younger than 47 Tuc. We show that the SRM method is
    insensitive to age for clusters with purely red HBs and ages as young
    as ~5 Gyr; for clusters with bluer HBs, the SRM method is only mildly
    sensitive to age differences between such clusters and the calibrating
    (standard) clusters. From these metallicity estimates, we conclude that
    the photometric abundances of the program clusters based on the
    properties of the RGB are systematically lower (Delta [Fe/H] = 0.1-0.4
    dex) than those derived using other indicators, in particular the Ca II
    triplet method. We note that the young globular cluster Palomar 12 also
    exhibits this behavior. We suggest that this discrepancy is due to
    systematic differences in the [alpha/Fe] ratios between the young
    clusters and the ``normal'' Galactic globulars used to calibrate the
    abundance determination methods. However, we are unable to completely
    reconcile all the observations of Rup 106 using this approach.
    Systematic differences in [alpha/Fe] between the young clusters and the
    rest of the Galactic globulars may indicate differences in their
    chemical enrichment histories, perhaps due to differing environments at
    the times of their formation. Interestingly, both Ter 7 and Arp 2 are
    believed to be members of the Sagittarius dwarf galaxy. (Copyright)
    1997 American Astronomical Society.