Kinematic Evidence for an Old Stellar Halo in the Large Magellanic Cloud
Dante Minniti,1*
Jura Borissova,1
Marina Rejkuba,2
David R. Alves,3
Kem H. Cook,4
Kenneth C. Freeman5
The oldest and most metal-poor Milky Way stars form a kinematically
hot halo, which motivates the two major formation scenarios
for our galaxy: extended hierarchical accretion and rapid collapse.
RR Lyrae stars are excellent tracers of old and metal-poor populations.
We measured the kinematics of 43 RR Lyrae stars in the inner
regions of the nearby Large Magellanic Cloud (LMC) galaxy. The
velocity dispersion equals 53 ± 10 kilometers per second,
which indicates that a kinematically hot metal-poor old halo
also exists in the LMC. This result suggests that our galaxy
and smaller late-type galaxies such as the LMC have similar
early formation histories.
2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany.
3 Columbia Astrophysics Laboratory, 550 West 120th Street, New York, NY 10027, USA.
4 Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
5 Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Canberra, ACT, Australia.
* To whom correspondence should be addressed. E-mail: dante{at}astro.puc.cl
