Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The low-mass IMF - deep star counts in the dSph galaxy Ursa Minor   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
colour-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 comparison of the low-mass stellar Initial
Mass Functions (IMF). We find that their LFs are identical within the
mass-range covered (~0.35 - 0.8 M_sun). 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. These results 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.

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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: q-bio
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The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
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The categories of this paper are: q-alg
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The categories of this paper are: econ