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Astron. Astrophys. 348, L49-L53 (1999)
Letter to the Editor
Evolution of the Galactic potential and halo streamers with future astrometric satellites
HongSheng Zhao 1,
Kathryn V. Johnston 2,
Lars Hernquist 3 and
David N. Spergel 4
1 Sterrewacht Leiden, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
2 Institute for Advanced Study, Princeton, NJ 08450, USA
3 University of California, Board of Studies in Astronomy and Astrophysics, Santa Cruz, CA 95064
4 Princeton University, Princeton University Observatory, Princeton, NJ 08540, USA
Received 25 May 1999 / Accepted 12 July 1999
Abstract
ESA's Global Astrometric Interferometer for Astrophysics (GAIA)
holds the promise of mapping out the detailed phase space structure of
the Galactic halo by providing unprecedented annual proper motion and
parallax of ![[FORMULA]](img1.gif)
astrometric accuracy
(Gilmore et al. 1998). Unlike NASA's Space Interferometry Mission
(SIM), which will achieve similar accuracies but is a pointed
instrument, GAIA will be able to construct a global catalogue of the
halo. Here we study proper motions of giant branch stars in a tidal
debris torn from a small satellite system in the halo. We follow the
evolution of a cold stream on a polar orbit between 8-50 kpc in a
variety of histories of the Galactic potential, and observe the bright
(![[FORMULA]](img2.gif)
mag) members of the debris tail with
GAIA accuracy. We simulate effects due to the growing or flipping of
the Galactic disk over the past 4 Gyrs or the perturbation from a
massive accreted lump such as the progenitor of the Magellanic Clouds.
Our simulations suggest that the results of Johnston, Zhao, Spergel
& Hernquist (1999) and Helmi, Zhao & de Zeeuw (1999) for
static Galactic potentials are likely to be largely generalizable to
realistic time-dependent potentials: a tidal debris remains cold in
spite of evolution and non-axial symmetry of the potential. GAIA
proper motion measurements of debris stars might be used to probe both
Galactic structure and Galactic history. We also study several other
factors influencing our ability to identify streams, including
accuracy of radial velocity and parallax data from GAIA, and
contamination from random field stars. We conclude that nearby, cold
streams could be detected with GAIA if these cousins of the
Sagittarius stream exist.
Key words: Galaxy:
evolution 
Galaxy:
formation
Galaxy: halo
Galaxy: kinematics and
dynamics
Galaxy:
structure
celestial mechanics, stellar dynamics
Send offprint requests to: Zhao (hsz@strw.leidenuniv.nl)
This article contains no SIMBAD objects.
Contents
- 1. Introduction
- 2. Streams in realistic time-varying potentials
- 3. Discussions of strategies
- 3.1. Why targeting streams?
- 3.2. Field contamination
- Acknowledgements
- References
© European Southern Observatory (ESO) 1999
Online publication: July 26, 1999
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