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The Low-Mass IMF - Deep Star Counts in the DSph Galaxy Ursa Minor

Feltzing, Sofia LU ; Wyse, R.; Houdashelt, M. and Gilmore, G. (2002) Workshop on Modes of Star Formation and the Origin of Field Populations In Modes of Star Formation and the Origin of Field Populations, ASP Conference Proceedings 285. p.223-229
Abstract
We present a new study of deep star counts in the Local Group dwarf spheroidal (dSph) in Ursa Minor. Both the luminosity function (LF) and the color-magnitude diagram (CMD) of the unevolved stars are compared with the LF and CMD of the old, metal-poor globular cluster M92. The main sequence locations and turn-offs are identical within the errors. Since we. know from the brighter evolved stars that the metallicities for these two disparate systems are the same this implies that they also have equal ages. A direct comparison of faint LFs is then equivalent to a comparison of the low-mass stellar initial mass functions (IMF). We find that the LFs are identical within the mass range covered (similar to 0.35 - 0.8 M-circle dot). The Ursa Minor... (More)
We present a new study of deep star counts in the Local Group dwarf spheroidal (dSph) in Ursa Minor. Both the luminosity function (LF) and the color-magnitude diagram (CMD) of the unevolved stars are compared with the LF and CMD of the old, metal-poor globular cluster M92. The main sequence locations and turn-offs are identical within the errors. Since we. know from the brighter evolved stars that the metallicities for these two disparate systems are the same this implies that they also have equal ages. A direct comparison of faint LFs is then equivalent to a comparison of the low-mass stellar initial mass functions (IMF). We find that the LFs are identical within the mass range covered (similar to 0.35 - 0.8 M-circle dot). The Ursa Minor dSph has one of the highest apparent M/L ratios known in the Local Group, and is an extremely low surface brightness external galaxy. M92 is a typical high surface brightness globular cluster, with no apparent dark matter. Our findings lead to the conclusion that the low-mass stellar IMF in systems that formed at high redshift is independent of environment. Indeed, it is consistent with the low-mass IMF in star-forming regions today. (Less)
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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
in
Modes of Star Formation and the Origin of Field Populations, ASP Conference Proceedings
editor
Grebel, Eva K.; Brandner., Walfgang; and
volume
285
pages
223 - 229
publisher
Astronomical Society of the Pacific
conference name
Workshop on Modes of Star Formation and the Origin of Field Populations
external identifiers
  • wos:000180752500032
ISBN
1-58381-128-1
language
English
LU publication?
yes
id
0d174221-c9c5-49f2-9494-0f62b6678c9a (old id 528004)
alternative location
http://adsabs.harvard.edu/abs/2001astro.ph..1370F
date added to LUP
2007-09-17 12:52:46
date last changed
2016-04-16 09:24:19
@inproceedings{0d174221-c9c5-49f2-9494-0f62b6678c9a,
  abstract     = {We present a new study of deep star counts in the Local Group dwarf spheroidal (dSph) in Ursa Minor. Both the luminosity function (LF) and the color-magnitude diagram (CMD) of the unevolved stars are compared with the LF and CMD of the old, metal-poor globular cluster M92. The main sequence locations and turn-offs are identical within the errors. Since we. know from the brighter evolved stars that the metallicities for these two disparate systems are the same this implies that they also have equal ages. A direct comparison of faint LFs is then equivalent to a comparison of the low-mass stellar initial mass functions (IMF). We find that the LFs are identical within the mass range covered (similar to 0.35 - 0.8 M-circle dot). The Ursa Minor dSph has one of the highest apparent M/L ratios known in the Local Group, and is an extremely low surface brightness external galaxy. M92 is a typical high surface brightness globular cluster, with no apparent dark matter. Our findings lead to the conclusion that the low-mass stellar IMF in systems that formed at high redshift is independent of environment. Indeed, it is consistent with the low-mass IMF in star-forming regions today.},
  author       = {Feltzing, Sofia and Wyse, R. and Houdashelt, M. and Gilmore, G.},
  booktitle    = {Modes of Star Formation and the Origin of Field Populations, ASP Conference Proceedings},
  editor       = {Grebel, Eva K. and Brandner., Walfgang},
  isbn         = {1-58381-128-1},
  language     = {eng},
  pages        = {223--229},
  publisher    = {Astronomical Society of the Pacific},
  title        = {The Low-Mass IMF - Deep Star Counts in the DSph Galaxy Ursa Minor},
  volume       = {285},
  year         = {2002},
}