Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Using VLBI Data to Investigate the Galaxy Structure in the
  Gravitationally Lensed System B1422+231   Gravitationally lensed systems with multiply imaged quasars are an excellent
tool for studying the properties of distant galaxies. In particular, they
provide the most accurate mass measures for the lensing galaxy. The system
B1422+231 is a well studied example of a quadruply imaged quasar, with
high-quality VLBI data available. Very accurate data on image positions, fluxes
and deconvolved image sizes provide good constraints for lensing models. We
discuss here the failure of smooth models in fitting the data. Since it is
intuitively clear that the mass of a lens galaxy is not a smooth entity, we
have investigated how deviation from a smooth model can influence lensing
phenomena, especially the image flux ratios. To explore expectations about the
level of substructure in galaxies and its influence on strong lensing, N-body
simulations of a model galaxy are employed. By using the mass distribution of
this model galaxy as a lens, synthetic data sets of different four image system
configurations are generated. Their analysis can possibly provide evidence for
the presence and strong influence of substructure in the primary lens galaxy.

22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th