Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Large-scale shock-ionized and photo-ionized gas in M83: the impact of
  star formation   We investigate the ionization structure of the nebular gas in M83 using the
line diagnostic diagram, [O III](5007 \degA)/H{\beta} vs. [S II](6716 \deg
A+6731 \deg A)/H{\alpha} with the newly available narrowband images from the
Wide Field Camera 3 (WFC3) of the Hubble Space Telescope (HST). We produce the
diagnostic diagram on a pixel-by-pixel (0.2" x 0.2") basis and compare it with
several photo- and shock-ionization models. For the photo-ionized gas, we
observe a gradual increase of the log([O III]/H{\beta}) ratios from the center
to the spiral arm, consistent with the metallicity gradient, as the H II
regions go from super solar abundance to roughly solar abundance from the
center out. Using the diagnostic diagram, we separate the photo-ionized from
the shock-ionized component of the gas. We find that the shock-ionized
H{\alpha} emission ranges from ~2% to about 15-33% of the total, depending on
the separation criteria used. An interesting feature in the diagnostic diagram
is an horizontal distribution around log([O III]/H{\beta}) ~ 0. This feature is
well fit by a shock-ionization model with 2.0 Z\odot metallicity and shock
velocities in the range of 250 km/s to 350 km/s. A low velocity shock
component, < 200 km/s, is also detected, and is spatially located at the
boundary between the outer ring and the spiral arm. The low velocity shock
component can be due to : 1) supernova remnants located nearby, 2) dynamical
interaction between the outer ring and the spiral arm, 3) abnormal line ratios
from extreme local dust extinction. The current data do not enable us to
distinguish among those three possible interpretations. Our main conclusion is
that, even at the HST resolution, the shocked gas represents a small fraction
of the total ionized gas emission at less than 33% of the total. However, it
accounts for virtually all of the mechanical energy produced by the central
starburst in M83.

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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th