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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:
Sag dSph CMa dSph
Substructures in the M31 halo
Galaxy formation mechanismsGalaxy formation mechanisms
Dimensions -->
Luminosity -->
Building blocks of the MW halo?Building blocks of the MW halo?
adapted fromBelokurov et al. 2007
GCsdSph’s
SDSS dSph’s
LeoT
BooII
Pulsating Variable Stars Pulsating Variable Stars ClassClass Periods Periods
(days)(days)MMVV PopPop Evo. PhaseEvo. Phase
CepheiCephei 1 – 1001 – 100 -7 -7 -2 -2 II Blue LoopBlue Loop
ScutiScuti < 0.5< 0.5 2 2 3 3 II MSMS
CepheiCephei < 0.3< 0.3 -4.5 -4.5 - -3.53.5
II MSMS
RV TauriRV Tauri 30 – 10030 – 100 -2 -2 -1 -1 I,III,II post-AGBpost-AGB
MiraMira > 100> 100 -2 -2 1 1 I,III,II AGBAGB
SemiregularSemiregularss
> 50> 50 -3 -3 1 1 I,III,II AGBAGB
RR LyraeRR Lyrae 0.3 – 10.3 – 1 0.0 0.0 1.0 1.0 IIII HBHB
W VirginisW Virginis 10 – 5010 – 50 -3 -3 -1 -1 IIII post-HBpost-HB
BL HerculisBL Herculis < 10< 10 -1 -1 0 0 IIII post-HBpost-HB
SX SX PhoenicisPhoenicis
< 0.1< 0.1 2 2 3 3 IIII MSMS
A.C.A.C. 0.3 - 2.50.3 - 2.5 -2 -2 0 0 ?? HBHB
RR LyraeRR Lyrae
Old Stars (> 10 Old Stars (> 10 Gyr)Gyr)
Horizontal branch Horizontal branch stars that lie in stars that lie in the instability the instability stripstrip
Radially pulsateRadially pulsate MMvv ≈ ≈ 0.60.6 (Smith 1995)
Bailey TypesBailey Types
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
OOIOOI OOII OOII
<P<Pabab>> .55d.55d .65d .65d
<P<Pcc>> .32d .37d.32d .37d
NNRRcRRc/N/Ntotaltotal .17.17 .44 .44[Fe/H][Fe/H] >-1.7>-1.7 <-1.7 <-1.7
(Oosterhoff 1939)
In the MW, most of the GCs with an RR Lyrae population divide into two distinct groups, based on <Pab>
Oo I <Pab> = 0.55 dOoII <Pab> = 0.65 d(Oosterhoff 1939)
And outside the Milky Way?
Galaxy formation mechanismsRR Lyrae starsRR Lyrae stars
Oo II
Oo I
Gap
Oosterhoff plane
Outside the Milky Way: the “old” dSph’s
adapted from Catelan, Greco et al. 2007
Oo II
Oo I
Gap
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
K. Kinemuchi - UWyoK. Kinemuchi - UWyoH.A. Smith – MSUH.A. Smith – MSUC. Rodgers – UWyoC. Rodgers – UWyoC. Kuehn – MSUC. Kuehn – MSUT.C. Beer – MSU/JINAT.C. Beer – MSU/JINAM. Catelan - PUCM. Catelan - PUCB.J. Pritzl - MacalesterB.J. Pritzl - Macalester
Telescope time
1.5m Loiano, 1.8m Lowell, 2.2m ESO, WIRO, INT, TNG, SOAR, WHT
Bootes
α((J2000) 14:00:06δ(J2000) 14:30:00Ellipticity 0.33 Rh 13′.0 ± 00′.7.7 Vtot(mag) 13.6 ± 0.5 mag[Fe/H] -2.00 ± 0.07 (m-M)o 18.9 ± 0.2 magmag
D 60 D 60 ± 6 KpcKpcMMV V -5.8 ± 0.5 mag0.5 magμV 28.3 ± 0.5 mag/arcsec-2
M/L 130-680 … along with the UMi dSph the most dark matter dominated object in the Universe!
Belokurov et al. 2006
Cycles of Discovery & Stellar PulsationCycles of Discovery & Stellar Pulsation
RRc
RRab
RRd
LPV
BFOSC - Loiano 1.52 m Bologna Observatory TelescopeWIRO-Prime - 2.3 m Wyoming Infrared ObservatoryDOLORES - TNG 3.5 m Italian National Telescope
Variable stars in Bootes
Oosterhoff II !!!!
<Pab> =0.64 d<Pc> =0.37 d
11 (15) RR Lyrae stars: 5RRab’s, 5RRc’s, 1RRd 1 LPV
Dall’Ora et al. 2006, ApJ, 653, L109
µ0 = 19.11 ± 0.08 mag D = 66 ± 6 Kpc
Siegel 2006, ApJ, 649, L83
Canes Venatici I
α(J2000) 13:28:03 δ(J2000) 33:33:21.0 Ellipticity 0.38 Rh 8′.5 ± 0′.5 Vtot(mag) 13.9 ± 0.5 magmag[Fe/H] -2.09 ± 0.02(m-M)o 21.75 ± 0.2 magmag
D 224 +22/-20 KpcD 224 +22/-20 KpcMMVV -7.9 ± 0.5 mag magμV 28.2 ± 0.5 mag/arcsec-2
M/L 221 ± 108108
Zucker et al. 2006
Variable Stars in CVn-IVariable Stars in CVn-I
RRab
RRc
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
<Pab> =0.60 d
µ0 = 21.11 ± 0.05 magD = 214 ± 25 Kpc 25 Kpc
23 RR Lyrae stars: 18 RRab’s, 5 RRc’s
3 ACs61 candidate variables
Oosterhoff Intermediate!!!!
Canes Venatici II
α(J2000) 12:57:10δ(J2000) 34:19:15Ellipticity 0.3 Rh 3′.0Vtot(mag) 15.1 ± 0.5 magmag[Fe/H] -2.31 ± 0.12 (m-M)o 20.9 ± 0.2 magmag
D 151 +15/-13 KpcD 151 +15/-13 KpcMMV V -4.8 ± 0.6 magmagμV 29.5 mag/arcsec-2
M/L 336 ± 240240
Belokurov et al. 2007
Variable stars in CVnII
RRab
RRc
WIRO -Prime -2.3 m Wyoming Infrared ObservatoryWHT - 4.2 m William Herschel Telescope La Palma
2 RR Lyrae stars: 1 RRab, 1 RRc<Pab> =0.75 d<Pc> =0.36 d
µ0 = 20.97 magD = 156 Kpc Kpc
Coma
α(J2000) 12:26:59δ (J2000) 23:54:15Ellipticity 0.5 Rh 5′.0Vtot(mag) 15.1 ± 0.5 magmag[Fe/H] -2.00 ± 0.07 (m-M)o 18.2 ± 0.2 magmag
D 44D 44 ± 4 Kpc KpcMMVV -3.7 ± 0.6 magmagμV 29.0 mag/arcsec-2
M/L 448 ± 297297
Belokurov et al. 2007
BFOSC - Loiano 1.52 m Bologna Observatory TelescopeWIRO-Prime - 2.3 m Wyoming Infrared ObservatoryINT – 2.5 Isaac Newton Telescope La Palma
Variable stars in Coma
RRab
RRc
SX Phe
2 RR Lyrae stars: 1 RRab, 1 RRc
1 SX Phe
<Pab> =0.67 d<Pc> =0.32 d
Variable stars in Coma
µ0 = 18.02 magD = 40 Kpc Kpc
UMa II
α(J2000) 08:51:30δ (J2000) 63:07:48Ellipticity 0.5Rh 13′.6Vtot(mag) 14.3 ± 0.5 magmag[Fe/H] -1.97 ± 0.15 (m-M)o 17.5 ± 0.3 magmag
D 32 +5/-4 KpcD 32 +5/-4 KpcMMVV -3.8 ± 0.6 magmagμ V 30.0 mag/arcsec-2
M/L 1722 ± 12261226
Zucker et al. 2006
Variable stars in UMaII
BFOSC - Loiano 1.52 m Bologna Observatory TelescopeLOWELL – 1.8 m TelescopeWIRO-Prime - 2.3 m Wyoming Infrared Observatory
1 RRab star
<Pab> =0.66 d
Variables in the SDSS dSph’s
Oosterhoff II !!!!
Summary
The SDSS new dSph’s in the Oosterhoff plane• Bootes
• Canes Venatici I• Canes Venatici II• Coma• UMa II
Oo IIOo IntermediateOo IIOo IIOo II
15 RR Lyrae stars48 “ 2 “ 2 “ 1 “
Canes Venatici I is like the old dwarf spheroidals in terms of variable stars.
The other SDSS dSph’s are more similar to the Milky Way GC’s.