Variable Stars in the Old Dwarf Spheroidal Galaxies, SDSS dSph’s, and Globular Clusters Charles Kuehn Michigan State University

 Cloud collapse  Merging Many observational evidences of merging:  Sag dSph  CMa dSph  Substructures in the M31 halo Galaxy formation mechanisms Galaxy formation mechanisms

Dimensions --> Luminosity --> Building blocks of the MW halo? adapted from Belokurov et al GCs dSph’s SDSS dSph’s LeoT BooII

Pulsating Variable Stars Class Periods (days) MVMVMVMVPop Evo. Phase  Cephei 1 –  -2 I Blue Loop  Scuti <  3 IMS  Cephei <  -3.5 IMS RV Tauri 30 –  -1 I,IIpost-AGB Mira >  1 I,IIAGB Semiregulars >  1 I,IIAGB RR Lyrae RR Lyrae 0.3 –  1.0 IIHB W Virginis 10 –  -1 IIpost-HB BL Herculis <  0 IIpost-HB SX Phoenicis <  3 IIMS A.C  0 ?HB

RR Lyrae Old Stars (> 10 Gyr) Old Stars (> 10 Gyr) Horizontal branch stars that lie in the instability strip Horizontal branch stars that lie in the instability strip Radially pulsate Radially pulsate M v ≈ 0.6 M v ≈ 0.6 (Smith 1995)

Bailey Types Based on shape of light curve Based on shape of light curve RRab pulsate in the fundamental mode RRab pulsate in the fundamental mode RRc pulsate in the first overtone RRc pulsate in the first overtone

Oosterhoff Groups In 1939 Oosterhoff noticed a division in the properties of globular cluster RR Lyraes In 1939 Oosterhoff noticed a division in the properties of globular cluster RR Lyraes OOI OOII.55d.65d.55d.65d.32d.37d.32d.37d N RRc /N total [Fe/H]> <-1.7 (Oosterhoff 1939)

In the MW, most of the GCs with an RR Lyrae population divide into two distinct groups, based on Oo I = 0.55 d OoII = 0.65 d (Oosterhoff 1939) And outside the Milky Way? Galaxy formation mechanisms RR Lyrae stars Oo II Oo I Gap Oosterhoff plane

Outside the Milky Way: the “ old ” dSph ’ s adapted from Catelan, Greco et al Oo II Oo I Gap

Field Stars in the Milky Way Halo The majority of the RRab stars fall along the Oosterhoff I line. The majority of the RRab stars fall along the Oosterhoff I line. Different from the stars seen in most dSphs which were Oosterhoff intermediate. Different from the stars seen in most dSphs which were Oosterhoff 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’s  metal poor (…as metal poor as stars in the MW halo…)  irregular shape distorted tidally interacting  host an ancient population The SDSS new dSph’s Bootes Canes Venatici I Canes Venatici II Coma UMa II

dSph GGCs SDSS dSph Dimensions --> Luminosity --> LeoT BooII Building blocks of the MW halo?

Variable stars in the new SDSS dSph’s Team G. Clementini - INAF OABo M. Dall’Ora - INAF OANa V. Ripepi - INAF OANa M. Marconi - INAF OANa I. Musella - INAF OANa C. Greco - INAF OABo L. Di Fabrizio – INAF La Palma K. Kinemuchi - UWyo H.A. Smith – MSU C. Rodgers – UWyo C. Kuehn – MSU T.C. Beer – MSU/JINA M. Catelan - PUC B.J. Pritzl - Macalester Telescope time 1.5m Loiano, 1.8m Lowell, 2.2m ESO, WIRO, INT, TNG, SOAR, WHT

Bootes ( α(J2000) 14:00:06 δ(J2000) 14:30:00 Ellipticity R h 13′.0 ± 0′.7 V tot (mag) 13.6 ± 0.5 mag [Fe/H] ± 0.07 mag (m-M) o 18.9 ± 0.2 mag D 60 Kpc D 60 ± 6 Kpc M V 0.5 mag M V -5.8 ± 0.5 mag μ V 28.3 ± 0.5 mag/arcsec -2 M/L … along with the UMi dSph the most dark matter dominated object in the Universe! Belokurov et al. 2006

Cycles of Discovery & Stellar Pulsation RRc RRab RRd LPV BFOSC - Loiano 1.52 m Bologna Observatory Telescope WIRO-Prime m Wyoming Infrared Observatory DOLORES - TNG 3.5 m Italian National Telescope Variable stars in Bootes

Oosterhoff II !!!! =0.64 d =0.37 d 11 (15) RR Lyrae stars: 5RRab’s, 5RRc’s, 1RRd 1 LPV Dall ’ Ora et al. 2006, ApJ, 653, L109 µ 0 = ± 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 R h 8′.5 ± 0′.5 mag V tot (mag) 13.9 ± 0.5 mag [Fe/H] ± 0.02 mag (m-M) o ± 0.2 mag D /-20 Kpc M V mag M V -7.9 ± 0.5 mag μ V 28.2 ± 0.5 mag/arcsec M/L 221 ± 108 Zucker et al. 2006

Variable Stars in CVn-I RRab RRc AC WIRO -Prime -2.3 m Wyoming Infrared Observatory DOLORES - TNG 3.5 m Italian National Telescope La Palma WHT m William Herschel Telescope La Palma

=0.60 d µ 0 = ± 0.05 mag 25 Kpc D = 214 ± 25 Kpc 23 RR Lyrae stars: 18 RRab’s, 5 RRc’s 3 ACs 61 candidate variables

Oosterhoff Intermediate!!!!

Canes Venatici II α(J2000) 12:57:10 δ(J2000) 34:19:15 Ellipticity 0.3 R h 3′.0 mag V tot (mag) 15.1 ± 0.5 mag [Fe/H] ± 0.12 mag (m-M) o 20.9 ± 0.2 mag D /-13 Kpc M V mag M V -4.8 ± 0.6 mag μ V 29.5 mag/arcsec M/L 336 ± 240 Belokurov et al. 2007

Variable stars in CVnII RRab RRc WIRO -Prime -2.3 m Wyoming Infrared Observatory WHT m William Herschel Telescope La Palma

2 RR Lyrae stars: 1 RRab, 1 RRc =0.75 d =0.36 d µ 0 = mag Kpc D = 156 Kpc

Coma α(J2000) 12:26:59 δ (J2000) 23:54:15 Ellipticity 0.5 R h 5′.0 mag V tot (mag) 15.1 ± 0.5 mag [Fe/H] ± 0.07 mag (m-M) o 18.2 ± 0.2 mag D 44 Kpc D 44 ± 4 Kpc M V mag M V -3.7 ± 0.6 mag μ V 29.0 mag/arcsec M/L 448 ± 297 Belokurov et al. 2007

BFOSC - Loiano 1.52 m Bologna Observatory Telescope WIRO-Prime m Wyoming Infrared Observatory INT – 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 =0.67 d =0.32 d

Variable stars in Coma µ 0 = mag Kpc D = 40 Kpc

UMa II α(J2000) 08:51:30 δ (J2000) 63:07:48 Ellipticity 0.5 R h 13′.6 mag V tot (mag) 14.3 ± 0.5 mag [Fe/H] ± 0.15 mag (m-M) o 17.5 ± 0.3 mag D 32 +5/-4 Kpc M V mag M V -3.8 ± 0.6 mag μ V 30.0 mag/arcsec M/L 1722 ± 1226 Zucker et al. 2006

Variable stars in UMaII BFOSC - Loiano 1.52 m Bologna Observatory Telescope LOWELL – 1.8 m Telescope WIRO-Prime m Wyoming Infrared Observatory 1 RRab star =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 II Oo Intermediate Oo II 15 RR Lyrae stars 48 “ 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.