Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey
  of the Magellanic Clouds   The EROS-2 project was designed to test the hypothesis that massive compact
halo objects (the so-called ``machos'') could be a major component of the dark
matter halo of the Milky Way galaxy. To this end, EROS-2 monitored over 6.7
years $33\times10^6$ stars in the Magellanic clouds for microlensing events
caused by such objects. In this work, we use only a subsample of $7\times10^6$
bright stars spread over $84 \deg^2$ of the LMC and $9 \deg^2$ of the SMC. The
strategy of using only bright stars helps to discriminate against background
events due to variable stars and allows a simple determination of the effects
of source confusion (blending). The use of a large solid angle makes the survey
relatively insensitive to effects that could make the optical depth strongly
direction dependent. Using this sample of bright stars, only one candidate
event was found, whereas $\sim39$ events would have been expected if the Halo
were entirely populated by objects of mass $M\sim0.4M_{\odot}$. Combined with
the results of EROS-1, this implies that the optical depth toward the Large
Magellanic Cloud (\object{LMC}) due to such lenses is $\tau<0.36\times10^{-7}$
(95%CL), corresponding to a fraction of the halo mass of less than 8%. This
optical depth is considerably less than that measured by the MACHO
collaboration in the central region of the LMC. More generally, machos in the
mass range $0.6\times10^{-7}M_\odot<M<15M_{\odot}$ are ruled out as the primary
occupants of the Milky Way Halo.

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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol