Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Compact Star Clusters in Nearby Dwarf Irregular Galaxies   Nearby dwarf irregular galaxies were searched for compact star clusters using
data from the HST archives. Three of the galaxies were found to host both
populous clusters (M_V<-9.5 at a fiducial age of 10 Myr) and super-star
clusters (M_V<-10.5 at 10 Myr). Four other dwarf galaxies, two of which contain
populous and super-star clusters, were drawn from the literature. We find upper
limits to integrated galactic M_B and star formation rate for the formation of
these clusters. However, galaxies brighter and more active than these limits
rarely form them. Yet when they do form, the associated star formation activity
is very high, with numerous compact clusters of similar age in the same complex
and often evidence for a galaxy-wide perturbation as the trigger. This tendency
to concentrate star formation in localized regions of high column density is
consistent with previous suggestions that self-gravity must be strong and the
pressure must be high to allow a cool phase of gas to exist in equilibrium.
Statistical considerations emphasize the peculiarity of super-star clusters in
dwarf galaxies, which are too small to sample the cluster mass function to that
extreme. We suggest that triggered large-scale flows and ambient gravitational
instabilities in the absence of shear make the clouds that form super-star
clusters in small galaxies. This is unlike the case in spirals where density
wave flows and scale-free compression from turbulence dominate. Further compar-
isons with spirals give insight into Larsen & Richtler's relation between star
formation rate per unit area and the fraction of young stars in massive dense
clusters. We suggest that this relation is the result of a physical connection
between maximum cluster mass, interstellar pressure, column density, and star
formation rate, combined with a size-of-sample effect.

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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ph
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas