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Date and Time of the Query: 2019-07-16 T10:13:27 PDT
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For refcode 2017ApJ...836...67H:
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2017ApJ...836...67H Galactic Dark Matter Halos and Globular Cluster Populations. III. Extension to Extreme Environments Harris, William E.; Blakeslee, John P.; Harris, Gretchen L. H. Abstract. The total mass {M}_{GCS_} in the globular cluster (GC) system of a galaxy is empirically a near-constant fraction of the total mass {M}_h_= {M}_{bary_}+{M}_{dark_} of the galaxy across a range of 10^5^ in galaxy mass. This trend is radically unlike the strongly nonlinear behavior of total stellar mass M_*_ versus M_ h_. We discuss extensions of this trend to two more extreme situations: (a) entire clusters of galaxies and (b) the ultra-diffuse galaxies (UDGs) recently discovered in Coma and elsewhere. Our calibration of the ratio {eta}_M_={M}_{GCS_}/{M}_h_ from normal galaxies, accounting for new revisions in the adopted mass-to-light ratio for GCs, now gives {eta}_M_=2.9x {10}^-5^ as the mean absolute mass fraction. We find that the same ratio appears valid for galaxy clusters and UDGs. Estimates of {eta}_M_ in the four clusters we examine tend to be slightly higher than for individual galaxies, but more data and better constraints on the mean GC mass in such systems are needed to determine if this difference is significant. We use the constancy of {eta}_M_ to estimate total masses for several individual cases; for example, the total mass of the Milky Way is calculated to be {M}_h_=1.1x {10}^12^ {M}_o_. Physical explanations for the uniformity of {eta}_M_ are still descriptive, but point to a picture in which massive dense star clusters in their formation stages were relatively immune to the feedback that more strongly influenced lower-density regions where most stars form. Key words: galaxies: formation, galaxies: star clusters: general, globular clusters: general
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