Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Pearson-Readhead Survey of Compact Extragalactic Radio Sources From
  Space. I. The Images   We present images from a space-VLBI survey using the facilities of the VLBI
Space Observatory Programme (VSOP), drawing our sample from the well-studied
Pearson-Readhead survey of extragalactic radio sources. Our survey has taken
advantage of long space-VLBI baselines and large arrays of ground antennas,
such as the Very Long Baseline Array and European VLBI Network, to obtain high
resolution images of 27 active galactic nuclei, and to measure the core
brightness temperatures of these sources more accurately than is possible from
the ground. A detailed analysis of the source properties is given in
accompanying papers. We have also performed an extensive series of simulations
to investigate the errors in VSOP images caused by the relatively large holes
in the (u,v) plane when sources are observed near the orbit normal direction.
We find that while the nominal dynamic range (defined as the ratio of map peak
to off-source error) often exceeds 1000:1, the true dynamic range (map peak to
on-source error) is only about 30:1 for relatively complex core-jet sources.
For sources dominated by a strong point source, this value rises to
approximately 100:1. We find the true dynamic range to be a relatively weak
function of the difference in position angle (PA) between the jet PA and (u,v)
coverage major axis PA. For low signal-to-noise regions typically located down
the jet away from the core, large errors can occur, causing spurious features
in VSOP images that should be interpreted with caution.

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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: comp-gas
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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: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-th
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an