Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Uncovering the Near-IR Dwarf Galaxy Population of the Coma Cluster with
  Spitzer IRAC   We present the first results of a Spitzer IRAC (Infrared Array Camera)
wide-field survey of the Coma cluster. The observations cover two fields of
different galaxy densities; the first is a 0.733 deg^2 region in the core of
the cluster (Coma 1), the second a 0.555 deg^2 off-center region located ~57
arcmin (1.7 Mpc) south-west from the core (Coma 3). The observations, although
short 70-90 s exposures, are very sensitive; we detect ~29,200 sources at 3.6
micron over the total ~1.3 deg^2 survey area. We construct 3.6 micron galaxy
luminosity functions (LFs) for each field using selection functions based on
spectroscopic redshifts. At the bright end, the LFs are well modeled by a
traditional Schechter function; [M^star (3.6 micron), alpha_1] = [-25.17,
-1.18] and [-24.69, -1.30] for Coma 1 and Coma 3 respectively. However, at the
faint end (M(3.6 micron) > -20.5), there is a steep increase in the LF slope in
both fields indicative of large numbers of red dwarf galaxies. The reality of
this population is examined using optical counterparts in SDSS data with
optical color filtering (g-r<1.3). The steep increase can be modeled with a
power-law function, with slopes of alpha_2 = -2.18 (Coma 1) and alpha_2 = -2.60
(Coma 3). A qualitative comparison with optical (B- and R-band) LFs shows that
we are likely to be observing a larger population of dwarf galaxies in the
near-IR, which may be a low-surface-brightness (LSB) population that IRAC is
particularly sensitive to, or a population too red to be detected in existing
optical surveys down to R~20.

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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: q-alg
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph