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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20140624T123000
DTEND;TZID=Atlantic/Canary:20140624T133000
UID:iactalks-649
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/649
CREATED:2014-06-24T12:30:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Andromeda II: a merger remnant or a product of tidal stirring 
DESCRIPTION:Andromeda II: a merger remnant or a product of tidal stirring \
 nDr. Ewa Lokas\n\nI will present an evolutionary model for the origin of A
 ndromeda II, a dSph satellite of M31, involving a merger between two disky
  dwarf galaxies than explains the origin of prolate rotation recently dete
 cted in the kinematic data for And II. The simulation traces the evolution
  of two dwarfs, whose structural parameters differ only in their disk scal
 e lengths, placed on a radial orbit towards each other with their angular 
 momenta inclined by 90 deg. After 5 Gyr the merger remnant forms a stable 
 triaxial galaxy with rotation only around the longest axis. This prolate r
 otation is naturally explained as due to the symmetry of the initial confi
 guration which leads to the conservation of angular momentum components al
 ong the direction of the merger. The stars originating from the two dwarfs
  show significantly different surface density profiles while having very s
 imilar kinematics in agreement with the properties of separate stellar pop
 ulations in And II. I will also discuss an alternative scenario for the fo
 rmation of And II, via tidal stirring of a disky dwarf galaxy. While intri
 nsic rotation occurs naturally in this model as a remnant of the initial r
 otation of the disk, it is mostly around the shortest axis of the stellar 
 component. The rotation around the longest axis is induced only occasional
 ly and remains much smaller that the system's velocity dispersion. I concl
 ude that although tidal origin of the velocity distribution in And II cann
 ot be excluded, it is much more naturally explained within the scenario in
 volving a past merger event. Thus, in principle, the presence of prolate r
 otation in dSph galaxies of the Local Group and beyond may be used as an i
 ndicator of major mergers in their history or even as a way to distinguish
  between the two scenarios of their formation.
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