Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First ground-based CCD proper motions for Fornax II: Final results   We present the first entirely ground-based astrometric determination of the
proper motion for the Fornax Local Group Dwarf Spheroidal satellite galaxy of
the Milky Way, using CCD data acquired with the ESO 3.5 m NTT telescope at La
Silla Observatory in Chile. Our unweighted mean from five Quasar fields in the
background of Fornax, used as fiducial reference points, leads to $\mu_\alpha
\cos \delta=0.62 \pm 0.16$ $\masy$, and $\mu_\delta=-0.53 \pm 0.15$ $\masy$. A
detailed comparison with all previous measurements of this quantity seems to
imply that there is still no convincing convergence to a single value, perhaps
indicating the existence of unnacounted systematic effects in (some of) these
measurements. From all available proper motion and radial velocity measurements
for Fornax, we compute Fornax's orbital parameters and their uncertainty using
a realistic Galactic potential and a Monte Carlo simulation. Properties of the
derived orbits are then compared to main star formation episodes in the history
of Fornax.
  All published proper motion values imply that Fornax has recently (200-300
Myr ago) approached perigalacticon at a distance of $\sim$150 kpc. However, the
derived period exhibits a large scatter, as does the apogalacticon. Our orbit,
being the most energetic, implies a very large apogalactic distance of $\sim
950$ kpc. If this were the case, then Fornax would be a representative of an
hypervelocity MW satellite in late infall.

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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: patt-sol