Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lensing and the Centers of Distant Early-Type Galaxies   Gravitational lensing provides a unique probe of the inner 10-1000 pc of
distant galaxies (z=0.2-1). Lens theory predicts that every strong lens system
should have a faint image near the center of the lens galaxy, which should be
visible in radio lenses but have not been observed. We study these ``core''
images using models derived from the stellar distributions in nearby early-type
galaxies. We find that realistic galaxies predict a remarkably wide range of
core images, with lensing magnifications spanning some six orders of magnitude.
More concentrated galaxies produce fainter core images, although not with any
simple, quantitative, model independent relation. Some real galaxies have
diffuse cores and predict bright core images (magnification mu>~0.1), but more
common are galaxies that predict faint core images (mu<~0.001). Thus, stellar
mass distributions alone are probably concentrated enough to explain the lack
of observed core images, and may require observational sensitivity to improve
by an order of magnitude before detections of core images become common.
Two-image lenses will tend to have brighter core images than four-image lenses,
so they will be the better targets for finding core images and exploiting these
tools for studying the central mass distributions of distant galaxies.

12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex