OLD MASSIVE GLOBULAR CLUSTERS AND THE STELLAR HALO OF THE DWARF STARBURST GALAXY NGC 4449

作者：Strader Jay^*; Seth Anil C; Caldwell Nelson

来源：Astronomical Journal, 2012, 143(2): 52.

DOI：10.1088/0004-6256/143/2/52

• galaxies: evolution
• galaxies: formation
• galaxies: individual (NGC 4449)
• galaxies: star clusters: general
• globular clusters: general

We use Hubble Space Telescope imaging to show that the nearby dwarf starburst galaxy NGC 4449 has an unusual abundance of luminous red star clusters. Joint constraints from integrated photometry, low-resolution spectroscopy, dynamical mass-to-light ratios, and resolved color magnitude diagrams provide evidence that some of these clusters are old globular clusters (GCs). Spectroscopic data for two massive clusters suggest intermediate metallicities ([Fe/H] similar to -1) and subsolar Mg enhancement ([Mg/Fe] similar to -0.1 to -0.2). One of these clusters may be the nucleus of a tidally disrupting dwarf galaxy; the other is very massive (similar to 3 x 10(6) M-circle dot). We have also identified a population of remote halo GCs. NGC 4449 is consistent with an emerging picture of the ubiquity of stellar halos among dwarf galaxies, and study of its GCs may help distinguish between accretion and in situ scenarios for such halos.

• 出版日期2012-2