Issue |
A&A
Volume 442, Number 1, October IV 2005
|
|
---|---|---|
Page(s) | 85 - 95 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20052921 | |
Published online | 30 September 2005 |
Hubble Space Telescope imaging of globular cluster candidates in low surface brightness dwarf galaxies
1
Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR, 369167, Russia
2
Isaac Newton Institute, Chile, SAO Branch
3
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD21218, USA e-mail: tpuzia@stsci.edu
Received:
22
February
2005
Accepted:
26
May
2005
Fifty-seven nearby low surface brightness dwarf galaxies () were searched for globular cluster candidates (GCCs) using Hubble Space Telescope WFPC2 imaging in V and I. The sample consists
of 18 dwarf spheroidal (dSph), 36 irregular (dIrr), and 3 “transition”
type (dIrr/dSph) galaxies with angular sizes less than 3.7 kpc situated at
distances
Mpc in the field and in the nearby groups: M 81,
Centaurus A, Sculptor, Canes Venatici I cloud. We find that ~50% of
dSph, dIrr/dSph, and dIrr galaxies contain GCCs. The fraction of GCCs
located near the center of dwarf spheroidal galaxies is
2 times
higher than for dIrrs. The mean integral color of GCCs in dSphs,
mag, coincides with the corresponding value for
Galactic globular clusters and is similar to the blue globular
cluster sub-populations in massive early-type galaxies. The color
distribution for GCCs in dIrrs shows a clear bimodality with peaks near
and 1.0 mag. Blue GCCs are presumably young with
ages
Gyr, while the red GCC population is likely to be older. The
detected GCCs have absolute visual magnitudes between
and -5
mag. We find indications for an excess population of faint GCCs with
mag in both dSph and dIrr galaxies, reminiscent of excess
populations of faint globular clusters in nearby Local Group spiral
galaxies. The measurement of structural parameters using King-profile
fitting reveals that most GCCs have structural parameters similar to
extended outer halo globular clusters in the Milky Way and M 31, as
well as the recently discovered population of “faint fuzzy” clusters in
nearby lenticular galaxies.
Key words: galaxies: dwarf / galaxies: star clusters
© ESO, 2005
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