Variable Stars in the Variable Stars in the Old Dwarf Spheroidal Old Dwarf Spheroidal Galaxies, SDSS dSph’s, Galaxies, SDSS dSph’s, and Globular Clusters and Globular Clusters Charles Kuehn Charles Kuehn Michigan State University Michigan State University
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Variable Stars in the Old Dwarf Spheroidal Galaxies, SDSS dSph’s, and Globular Clusters Charles Kuehn Michigan State University.
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Variable Stars in the Old Variable Stars in the Old Dwarf Spheroidal Galaxies, Dwarf Spheroidal Galaxies, SDSS dSph’s, and Globular SDSS dSph’s, and Globular
ClustersClusters
Charles KuehnCharles KuehnMichigan State UniversityMichigan State University
Cloud collapse
Merging
Many observationalMany observationalevidences of merging:evidences of merging:
Based on shape Based on shape of light curveof light curve
RRab pulsate in RRab pulsate in the fundamental the fundamental modemode
RRc pulsate in RRc pulsate in the first overtonethe first overtone
Oosterhoff GroupsOosterhoff Groups
In 1939 Oosterhoff In 1939 Oosterhoff noticed a division in noticed a division in the properties of the properties of globular cluster RR globular cluster RR LyraesLyraes
Field Stars in the Milky Way HaloField Stars in the Milky Way Halo
The majority of The majority of the RRab stars the RRab stars fall along the fall along the Oosterhoff I Oosterhoff I line.line.
Different from Different from the stars seen the stars seen in most dSphs in most dSphs which were which were Oosterhoff Oosterhoff intermediate.intermediate.
(Courtesy of N. DeLee)
fainter than previously known dSph’s: fainter than previously known dSph’s: V>28 mag/arcsec-2
properties intermediate between GCs and dSph’sproperties intermediate between GCs and dSph’s metal poor (…as metal poor as stars in the MW halo…)metal poor (…as metal poor as stars in the MW halo…) irregular shape distorted tidally interactingirregular shape distorted tidally interacting host an ancient population host an ancient population
The SDSS new dSph’s
• Bootes • Canes Venatici I• Canes Venatici II• Coma• UMa II
dSphGGCs
SDSS dSph
Dimensions -->
Luminosity -->
LeoT
BooII
Building blocks of the MW halo?Building blocks of the MW halo?
Variable stars in the new SDSS dSph’s
Team
G. Clementini - INAF OABoG. Clementini - INAF OABoM. Dall’Ora - INAF OANaM. Dall’Ora - INAF OANaV. Ripepi - INAF OANaV. Ripepi - INAF OANaM. Marconi - INAF OANaM. Marconi - INAF OANaI. Musella - INAF OANa I. Musella - INAF OANa C. Greco - INAF OABo C. Greco - INAF OABo L. Di Fabrizio – INAF La PalmaL. Di Fabrizio – INAF La Palma
ACWIRO -Prime -2.3 m Wyoming Infrared ObservatoryDOLORES - TNG 3.5 m Italian National Telescope La PalmaWHT - 4.2 m William Herschel Telescope La Palma