FIRST GROUND-BASED CHARGE-COUPLED DEVICE PROPER MOTIONS FOR FORNAX. II. FINAL RESULTS
- Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile)
- Instituto de Astrofisica de Canarias, Tenerife 38200, Islas Canarias (Spain)
- Departamento de Fisica, Universidad de Tarapaca, Casilla 7-D, Arica (Chile)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- Zentrum fuer Astronomie, Moenchhofstr. 12-14, 69120 Heidelberg (Germany)
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 (MW), using charge-coupled device data acquired with the ESO 3.5 m New Technology 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}{sub {alpha}c}os {delta} = 0.62 {+-} 0.16 mas yr{sup -1} and {mu}{sub {delta}} = -0.53 {+-} 0.15 mas yr{sup -1}. 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 unaccounted 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 {approx}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 {approx}950 kpc. If this were the case, then Fornax would be a representative of a hypervelocity MW satellite in late infall.
- OSTI ID:
- 21582880
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 142, Issue 3; Other Information: DOI: 10.1088/0004-6256/142/3/93; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ASTROPHYSICS
CHARGE-COUPLED DEVICES
COMPUTERIZED SIMULATION
DISTANCE
MILKY WAY
MONTE CARLO METHOD
ORBITS
PROPER MOTION
QUASARS
RADIAL VELOCITY
SATELLITES
STARS
TELESCOPES
CALCULATION METHODS
COSMIC RADIO SOURCES
GALAXIES
MOTION
PHYSICS
SEMICONDUCTOR DEVICES
SIMULATION
VELOCITY