Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HST/WFPC2 and VLT/ISAAC observations of PROPLYDS in the giant HII region
  NGC 3603   We report the discovery of three proplyd-like structures in the giant HII
region NGC 3603. The emission nebulae are clearly resolved in narrow-band and
broad-band HST/WFPC2 observations in the optical and broad-band VLT/ISAAC
observations in the near-infrared. All three nebulae are tadpole shaped, with
the bright ionization front at the head facing the central cluster and a
fainter ionization front around the tail pointing away from the cluster.
Typical sizes are 6,000 A.U. x 20,000 A.U. The nebulae share the overall
morphology of the proplyds (``PROto PLanetarY DiskS'') in Orion, but are 20 to
30 times larger in size. Additional faint filaments located between the nebulae
and the central ionizing cluster can be interpreted as bow shocks resulting
from the interaction of the fast winds from the high-mass stars in the cluster
with the evaporation flow from the proplyds. The striking similarity of the
tadpole shaped emission nebulae in NGC 3603 to the proplyds in Orion suggests
that the physical structure of both types of objects might be the same. We
present 2D radiation hydrodynamical simulations of an externally illuminated
star-disk-envelope system, which was still in its main accretion phase when
first exposed to ionizing radiation from the central cluster. The simulations
reproduce the overall morphology of the proplyds in NGC 3603 very well, but
also indicate that mass-loss rates of up to 10^-5 Mo/yr are required in order
to explain the size of the proplyds. (abbreviated)

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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: acc-phys