Chemical evolution of the high redshift galaxies |
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Authors: | Pushpa Khare N C Rana |
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Institution: | (1) Inter University Centre for Astronomy and Astrophysics, Ganeshkhind, Post Bag 4, 411 007 Pune;(2) Present address: Physics Department, Utkal University, 751004 Bhubaneswar |
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Abstract: | We have tried to determine the rate of chemical evolution of high redshift galaxies from the observed redshift distribution
of the heavy element absorption systems in the spectra of QSOs, taking into account the evolution in the intensity of the
metagalactic UV ionizing radiation background, the radius and/or the co-moving number density of, and the fraction of mass
in the form of gas in, the absorbers. The data for both the Lyman limit systems and the C IV systems have been fitted simultaneously.
It seems that the abundance of carbon has possibly increased by about a factor of 5 to 20 from the cosmic time corresponding
to the redshift ≃ 4 to 2. The data also suggest that either the radius or the co-moving number density of the galaxies increased
with redshift up to z = 2.0 and decreased slowly thereafter. The total mass of the halo gas was higher in the past, almost
equal to the entire mass of the galaxy at z = 4. The hydrogen column density distribution for Lyman limit systems predicted
by the model is in agreement with the observed distribution. |
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Keywords: | High redshift galaxies chemical evolution Lyman limitsystems CIV absorption systems diffuse UV radiation background |
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