Just noticed a paper from Astro-ph mailing list. It is the "UCD" abbreviation in the title that calls my attention. After reading the abstract, I know, "UCD" here is completely different from the IVOA UCD.
Should we try to avoid abbreviation collision at least in Astronomy? How to get it?
Cheers,
Title: An extreme IMF as an explanation for high M/L ratios in UCDs? The CO
index as a tracer of bottom heavy IMFs
Authors: Steffen Mieske, Pavel Kroupa
Categories: astro-ph
Comments: 7 pages, 5 figures, accepted for publication in ApJ
\\
A new type of compact stellar systems, labelled ``ultra-compact dwarf
galaxies'' (UCDs), was discovered in the last decade. Recent studies show that
their dynamical mass-to-light ratios (M/L) tend to be too high to be explained
by canonical stellar populations, being on average about twice as large as
those of Galactic globular clusters of comparable metallicity. If this offset
is caused by dark matter in UCDs, it would imply dark matter densities as
expected for the centers of cuspy dark matter halos, incompatible with cored
dark matter profiles. Investigating the nature of the high M/L ratios in UCDs
therefore offers important constraints on the phase space properties of dark
matter particles. Here we describe an observational method to test whether a
bottom-heavy IMF may cause the high M/L ratios of UCDs. We propose to use the
CO index at 2.3mu -- which is sensitive to the presence of low-mass stars -- to
test for a bottom heavy IMF. In the case that the high M/L ratios are caused by
a bottom-heavy IMF, we show that the equivalent width of the CO index will be
up to 30% weaker in UCDs compared to sources with similar metallicity that have
canonical IMFs. We find that these effects are well detectable with current
astronomical facilities in a reasonable amount of time (a few hours to nights).
Measuring the CO index of UCDs hence appears a promising tool to investigate
the origin of their high M/L ratios.
\\ ( http://arxiv.org/abs/0712.1821 , 106kb)
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