Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Interstellar Medium of Lens Galaxies   We use observations from the CASTLES survey of gravitational lenses to study
extinction in 23 lens galaxies with $0 < z_l < 1$. The median differential
extinction between lensed images is $\Delta E(\bv) = 0.05$ mag, and the
directly measured extinctions agree with the amount needed to explain the
differences between the statistics of radio and (optical) quasar lens surveys.
We also measure the first extinction laws outside the local universe, including
an $R_V=7.2$ curve for a molecular cloud at $z_l=0.68$ and an $R_V=1.5$ curve
for the dust in a redshift $z_l=0.96$ elliptical galaxy.

26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th