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.