Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discs in early-type lensing galaxies: effects on magnification ratios
  and measurements of $H_0$   Observations of early-type galaxies, both in the local universe and in
clusters at medium redshifts, suggest that these galaxies often contain discs
or disc-like structures. Using the results of Kelson et al. (2000) for the
incidence of disc-components among the galaxies in the redshift z=0.33 cluster
CL 1358+62, we investigate the effect of disc structures on the lensing
properties of early-type galaxies. Statistical properties, like magnification
cross sections and the expected number of quad (four-image) lens systems, are
not affected greatly by the inclusion of discs that contain less than about 10
per cent of the total stellar mass. However, the properties of individual lens
systems are affected. We estimate that 10-30 per cent of all quad lens systems,
with early-type deflector galaxies, would be affected measurably by the
presence of disc components. Intriguingly, the image magnification ratios are
altered significantly. The amplitude of the predicted change is sufficient to
explain the observed magnification ratios in systems like B1422+231 without
requiring compact substructure. Furthermore, time delays between images also
change; fitting a bulge-only model to early-type lenses that in fact contain a
disc would yield a value of the Hubble constant H_0 that is systematically too
low by about 25 per cent.

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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
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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: dg-ga
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an