Bibcode
Fouquet, Sylvain; Hidalgo, S. L.; Łokas, Ewa L.; del Pino, Andrés
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 469, Issue 4, p.4999-5015
Fecha de publicación:
8
2017
Número de citas
14
Número de citas referidas
11
Descripción
We analyse in detail the spatial distribution and kinematic properties
of two different stellar populations in Andromeda II dwarf spheroidal
galaxy. We obtained their detailed surface density maps together with
their radial density profiles. The two populations differ not only in
age and metallicity, but also in their spatial distribution and
kinematics. Old stars (≳11 Gyr) follow a round distribution well
fitted by truncated density profiles. These stars rotate around the
projected optical major axis of the galaxy with line-of-sight velocities
vlos(rh) = 16 ± 3 km s-1 and a
velocity gradient of 2.06 ± 0.21 km s-1
arcmin-1. Intermediate-age stars (≲9 Gyr) concentrate in
the centre of the galaxy and form an elongated structure extending along
the projected optical major axis. This structure appears to rotate with
a velocity gradient of 2.24 ± 0.22 km s-1
arcmin-1 and around the optical minor axis. The centres of
rotation and kinetic position angles (PAkin) of both
populations differ. For intermediate-age stars we obtained
PAkin = 18° ± 2° and for the old ones
PAkin = 63° ± 3° in good agreement with
photometric PA measured from isopleths fitted to the photometry. We
conclude that the two stellar populations may not be fully relaxed and
thus be the result of a merger occurred at redshift z ˜ 1.75.
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