Bibcode
DOI
Spitler, Lee R.; Larsen, Søren S.; Strader, Jay; Brodie, Jean P.; Forbes, Duncan A.; Beasley, Michael A.
Referencia bibliográfica
The Astronomical Journal, Volume 132, Issue 4, pp. 1593-1609.
Fecha de publicación:
10
2006
Número de citas
111
Número de citas referidas
102
Descripción
A detailed imaging analysis of the globular cluster (GC) system of the
Sombrero galaxy (NGC 4594) has been accomplished using a six-image
mosaic from the Hubble Space Telescope Advanced Camera for Surveys. The
quality of the data is such that contamination by foreground stars and
background galaxies is negligible for all but the faintest 5% of the GC
luminosity function. This enables the study of an effectively pure
sample of 659 GCs until ~2 mag fainter than the turnover magnitude,
which occurs at MTOMV=-7.60+/-0.06 for an assumed
m-M=29.77. Two GC metallicity subpopulations are easily distinguishable,
with the metal-poor subpopulation exhibiting a smaller intrinsic
dispersion in color compared to the metal-rich subpopulation. There are
three new discoveries. (1) A metal-poor GC color-magnitude trend has
been observed. (2) The fact that the metal-rich GCs are ~17% smaller
than the metal-poor ones for small projected galactocentric radii (less
than ~2') has been confirmed. However, the median half-light radii of
the two subpopulations become identical at ~3' from the center. This is
most easily explained if the size difference is the result of projection
effects. (3) The brightest (MV<-9.0) members of the GC
system show a size-magnitude upturn, where the average GC size increases
with increasing luminosity. Evidence is presented that supports an
intrinsic origin for this feature rather than being a result of accreted
dwarf elliptical nuclei. In addition, the metal-rich GCs show a
shallower positive size-magnitude trend, similar to what is found in
previous studies of young star clusters.
Based on observations made with the NASA/ESA Hubble Space Telescope,
obtained (from the data archive) at the Space Telescope Science
Institute, which is operated by the Association of Universities for
Research in Astronomy, Inc., under NASA contract NAS5-26555. These
observations are associated with program 9714.