Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measuring the undetectable: Proper motions and parallaxes of very faint
  sources   The near future of astrophysics involves many large solid-angle, multi-epoch,
multi-band imaging surveys. These surveys will, at their faint limits, have
data on large numbers of sources that are too faint to be detected at any
individual epoch. Here we show that it is possible to measure in multi-epoch
data not only the fluxes and positions, but also the parallaxes and proper
motions of sources that are too faint to be detected at any individual epoch.
The method involves fitting a model of a moving point source simultaneously to
all imaging, taking account of the noise and point-spread function in each
image. By this method it is possible to measure the proper motion of a point
source with an uncertainty close to the minimum possible uncertainty given the
information in the data, which is limited by the point-spread function, the
distribution of observation times (epochs), and the total signal-to-noise in
the combined data. We demonstrate our technique on multi-epoch Sloan Digital
Sky Survey imaging of the SDSS Southern Stripe. We show that we can distinguish
very red brown dwarfs by their proper motions from very high-redshift quasars
more than $1.6\mag$ fainter than with traditional technique on these SDSS data,
and with better better fidelity than by multi-band imaging alone. We
re-discover all 10 known brown dwarfs in our sample and present 9 new candidate
brown dwarfs, identified on the basis of high proper motion.

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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph