Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hydrodynamic Simulations of Galaxy Formation. II. Photoionization and
  the Formation of Low Mass Galaxies   Photoionization by the high-redshift ultraviolet radiation background heats
low density gas before it falls into dark matter potential wells, and it
eliminates the neutral hydrogen and singly ionized helium that dominate cooling
of primordial gas at temperatures of $10^4-10^5$K. We investigate the influence
of photoionization on galaxy formation using high-resolution simulations with a
1-dimensional, spherically symmetric, Lagrangian hydrodynamics/gravity code. We
find that the presence of a photoionizing background suppresses the formation
of galaxies with circular velocities $v_{circ} \simlt 30\,$\kms\ and
substantially reduces the mass of cooled baryons in systems with circular
velocities up to $v_{circ} \sim 50\,$\kms. Above $v_{circ} \sim 75\,$\kms,
photoionization has no significant effect. Photoionization exerts its influence
primarily by heating gas before collapse; the elimination of line cooling
processes is less important. We discuss the implications of these results for
hierarchical theories of galaxy formation.

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The categories of this paper are: eess
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The categories of this paper are: adap-org
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys