Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Elucidating the Correlation of the Quasar \ion{Fe}{2}/\ion{Mg}{2} Ratio
  with Redshift   Interpretation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios from
quasars has a major cosmological motivation. Both Fe and Mg are produced by
short-lived massive stars. In addition, Fe is produced by accreting white dwarf
supernovae somewhat after star formation begins. Therefore, we expect that the
Fe/Mg ratio will gradually decrease with redshift. We have used data from the
Sloan Digital Sky Survey to explore the dependence of the
\ion{Fe}{2}(UV)/\ion{Mg}{2} ratio on redshift and on luminosity in the redshift
range of $0.75< z< 2.20$, and we have used predictions from our 830-level model
for the \ion{Fe}{2} atom in photoionization calculations to interpret our
findings.
  We have split the quasars into several groups based upon the value of their
\ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios, and then checked to see how the
fraction of quasars in each group varies with the increase of redshift. We next
examined the luminosity dependence of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio,
and we found that beyond a threshold of \ion{Fe}{2}(UV)/\ion{Mg}{2} =~ 5, and
$M_{2500} < -25\rm mag$, the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio increases with
luminosity, as predicted by our model.
  We interpret our observed variation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio
with redshift as a result of the correlation of redshift with luminosity in a
magnitude limited quasar sample.

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The categories of this paper are: math
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
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The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
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The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph