Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Distinguishing between HII regions and planetary nebulae with Hi-GAL,
  WISE, MIPSGAL, and GLIMPSE   HII regions and planetary nebulae (PNe) both emit at radio and infrared (IR)
wavelengths, and angularly small HII regions can be mistaken for PNe. This
problem of classification is most severe for HII regions in an early
evolutionary stage, those that are extremely distant, or those that are both
young and distant. Using data from the Herschel Hi-GAL survey, as well as WISE
and the Spitzer MIPSGAL and GLIMPSE surveys, we wish to establish
characteristic IR colors that can be used to distinguish between HII regions
and PNe. We perform aperture photometry measurements for a sample of 126 HII
regions and 43 PNe at wavelengths from 8.0 micron to 500 micron. We find that
HII regions and PNe have distinct IR colors. The most robust discriminating
color criteria are [F12/F8] < 0.3, [F160/F12] > 1.3, and [F160/F24] > 0.8 (or
alternately [F160/F22] > 0.8), where the brackets indicate the log of the flux
ratio. All three of these criteria are individually satisfied by over 98% of
our sample of HII regions and by about 10% of our sample of PNe. Combinations
of these colors are more robust in separating the two populations; for example
all HII regions and no PNe satisfy [F12/F8] < 0.4 and [F160/F22] > 0.8. When
applied to objects of unknown classification, these criteria prove useful in
separating the two populations. The dispersion in color is relatively small for
HII regions; this suggests that any evolution in these colors with time for HII
regions must be relatively modest. The spectral energy distributions (SEDs) of
HII regions can be separated into "warm" and "cold" components. The "cold"
component is well-fit by a grey-body of temperature 25K. The SEDs of nearly
two-thirds of our sample of HII regions peak at 160 micron and one third peak
at 70 micron. For PNe, 67% of the SEDs peak at 70 micron, 23% peak at either 22
micron or 24 micron, and 9% (two sources) peak at 160 micron.

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The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg