Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The relationship between star formation rates and mid-infrared emission
  in galactic disks   The Halpha and mid-infrared mean disk surface brightnesses are compared in a
sample of nearby spirals observed by ISOCAM. This shows that, in spiral disks,
dust emission at 7 and 15 microns provides a reasonable star formation tracer.
The fact that the 15 to 7 micron flux ratio is nearly constant in various
global exciting conditions indicates a common origin, namely the aromatic
infrared band carriers, and implies that at these wavelengths, dust emission
from the disks of normal galaxies is dominated by photodissociation regions and
not by HII regions themselves. We use this newly-found correlation between the
mid-infrared and the Halpha line to investigate the nature of the link between
the far-infrared (60 and 100 microns) and Halpha. Although the separation of
the central regions from the disk is impossible to achieve in the far-infrared,
we show that a circumnuclear contribution to the dust emission, having no
equivalent counterpart in Halpha, is most likely responsible for the well-known
non-linearity between far-infrared and Halpha fluxes in spiral galaxies. We
derive a calibration of 7 and 15 micron fluxes in terms of star formation rates
from a primary calibration of Halpha in the literature, and also outline the
applicability limits of the proposed conversion, which should not be blindly
extrapolated to objects whose nature is unknown.

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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph