Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lyman Alpha Radiation From Collapsing Protogalaxies I: Characteristics
  of the Emergent Spectrum   We present Monte Carlo calculations of Lyman alpha (Lya) radiative transfer
through collapsing gas clouds, representing proto-galaxies that are caught in
the process of their assembly. Such galaxies produce Lya flux over an extended
solid angle from a spatially extended Lya emissivity and/or from scattering
effects. We study the effect of the gas distribution and kinematics, and of the
Lya emissivity profile, on the emergent spectrum and surface brightness
distribution. The emergent Lya spectrum is typically double-peaked and
asymmetric. In practice, the blue peak is significantly enhanced and the red
peak, in most cases, will be undetectable. The resulting effective blueshift,
combined with scattering in the intergalactic medium, will render extended Lya
emission from collapsing protogalaxies difficult to detect beyond redshift z=4.
The surface brightness distribution is typically flat, and a strong wavelength
dependence of its slope (with preferential flattening at the red side of the
line) would be a robust indication that Lya photons are being generated (rather
than just scattered) in a spatially extended region around the galaxy. We also
find that for self-ionized clouds whose effective Lya optical depth is less
than 10^3, infall and outflow models can produce nearly identical spectra and
surface brightness distributions, and are difficult to distinguish from one
another. The presence of deuterium with a cosmic abundance may produce a narrow
but detectable dip in the spectra of systems with moderate hydrogen column
densities, in the range 10^18-10^20 cm^-2. Finally, we present a new analytic
solution for the emerging Lya spectrum in the limiting case of a static uniform
sphere, extending previous solutions for static plane-parallel slabs.

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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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The categories of this paper are: cond-mat
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The categories of this paper are: q-alg
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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: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th