First ground-based charge-coupled device proper motions for fornax

• Verfasst von: Mendez, Rene A. [VerfasserIn]
• Verfasst von: Costa, Edgardo [VerfasserIn]
• Verfasst von: Gallart, Carme [VerfasserIn]
• Verfasst von: Pedreros, Mario H. [VerfasserIn]
• Verfasst von: Moyano, Maximiliano [VerfasserIn]
• Verfasst von: Altmann, Martin [VerfasserIn]
• Titel: First ground-based charge-coupled device proper motions for fornax
• Titelzusatz: II. final results
• Verf.angabe: René A. Méndez, Edgardo Costa, Carme Gallart, Mario H. Pedreros, Maximiliano Moyano, and Martin Altmann
• E-Jahr: 2011
• Jahr: 2011 August 16
• Umfang: 12 S.
• Fussnoten: Gesehen am 17.08.2022
• Titel Quelle: Enthalten in: The astronomical journal
• Ort Quelle: London : Institute of Physics Publ., 1998
• Jahr Quelle: 2011
• Band/Heft Quelle: 142(2011), 3, Artikel-ID 93, Seite 1-12
• ISSN Quelle: 1538-3881
• DOI: doi:10.1088/0004-6256/142/3/93
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1814556192

Abstract

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 μαcos δ = 0.62 ± 0.16 mas yr−1 and μδ = −0.53 ± 0.15 mas yr−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 ∼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 ∼950 kpc. If this were the case, then Fornax would be a representative of a hypervelocity MW satellite in late infall.