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Variable Stars in the Old Dwarf Spheroidal Galaxies, SDSS dSph’s, and Globular Clusters

Variable Stars in the Old Dwarf Spheroidal Galaxies, SDSS dSph’s, and Globular Clusters. Charles Kuehn Michigan State University. Many observational evidences of merging:. Sag dSph. CMa dSph. Substructures in the M31 halo. Galaxy formation mechanisms. Cloud collapse. Merging.

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Variable Stars in the Old Dwarf Spheroidal Galaxies, SDSS dSph’s, and Globular Clusters

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

  2. Many observationalevidences of merging: • Sag dSph • CMa dSph • Substructures in the M31 halo Galaxy formation mechanisms • Cloud collapse • Merging

  3. Building blocks of the MW halo? dSph’s GCs Luminosity --> LeoT SDSS dSph’s BooII adapted from Belokurov et al. 2007 Dimensions -->

  4. Pulsating Variable Stars

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

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

  7. Oosterhoff Groups • In 1939 Oosterhoff noticed a division in the properties of globular cluster RR Lyraes OOI OOII <Pab> .55d .65d <Pc> .32d .37d NRRc/Ntotal .17 .44 [Fe/H] >-1.7 <-1.7 (Oosterhoff 1939)

  8. Galaxy formation mechanisms Oosterhoff plane RR Lyrae stars 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 d OoII <Pab> = 0.65 d (Oosterhoff 1939) Oo II Gap Oo I And outside the Milky Way?

  9. adapted from Catelan, Greco et al. 2007 Outside the Milky Way: the “old” dSph’s Oo II Gap Oo I

  10. Field Stars in the Milky Way Halo • The majority of the RRab stars fall along the Oosterhoff I line. • Different from the stars seen in most dSphs which were Oosterhoff intermediate. (Courtesy of N. DeLee)

  11. The SDSS new 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 • Bootes • Canes Venatici I • Canes Venatici II • Coma • UMa II

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

  13. 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

  14. Bootes α(J2000) 14:00:06 δ(J2000) 14:30:00 Ellipticity 0.33 Rh 13′.0±0′.7 Vtot(mag) 13.6 ± 0.5 mag [Fe/H] -2.00 ± 0.07 (m-M)o 18.9 ± 0.2mag D 60 ± 6Kpc MV -5.8±0.5 mag μV 28.3± 0.5mag/arcsec-2 M/L 130-680 … along with the UMi dSph the most dark matter dominated object in the Universe! Belokurov et al. 2006

  15. Variable stars in Bootes RRc RRab RRd LPV BFOSC - Loiano 1.52 m Bologna Observatory Telescope WIRO-Prime - 2.3 m Wyoming Infrared Observatory DOLORES - TNG 3.5 m Italian National Telescope Cycles of Discovery & Stellar Pulsation

  16. 11 (15) RR Lyrae stars: 5RRab’s, 5RRc’s, 1RRd 1 LPV <Pab> =0.64 d <Pc> =0.37 d µ0 = 19.11 ± 0.08 mag D = 66 ± 6 Kpc Dall’Ora et al. 2006, ApJ, 653, L109 Siegel 2006, ApJ, 649, L83 Oosterhoff II !!!!

  17. 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 ± 0.5mag [Fe/H] -2.09 ± 0.02 (m-M)o 21.75 ± 0.2mag D 224 +22/-20 Kpc MV-7.9± 0.5 mag μV28.2 ± 0.5 mag/arcsec-2 M/L 221±108 Zucker et al. 2006

  18. 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 - 4.2 m William Herschel Telescope La Palma

  19. µ0 = 21.11 ± 0.05 mag D = 214± 25 Kpc 23 RR Lyrae stars: 18 RRab’s, 5 RRc’s 3 ACs 61 candidatevariables <Pab> =0.60 d

  20. Oosterhoff Intermediate!!!!

  21. Canes Venatici II α(J2000) 12:57:10 δ(J2000) 34:19:15 Ellipticity 0.3 Rh 3′.0 Vtot(mag) 15.1 ± 0.5mag [Fe/H] -2.31 ± 0.12 (m-M)o 20.9 ± 0.2 mag D 151 +15/-13 Kpc MV -4.8 ± 0.6 mag μV29.5 mag/arcsec-2 M/L 336±240 Belokurov et al. 2007

  22. Variable stars in CVnII RRab RRc WIRO -Prime -2.3 m Wyoming Infrared Observatory WHT - 4.2 m William Herschel Telescope La Palma

  23. 2 RR Lyrae stars: 1 RRab, 1 RRc µ0 = 20.97 mag D = 156 Kpc <Pab> =0.75 d <Pc> =0.36 d

  24. Coma α(J2000) 12:26:59 δ (J2000) 23:54:15 Ellipticity 0.5 Rh 5′.0 Vtot(mag) 15.1 ± 0.5mag [Fe/H] -2.00 ± 0.07 (m-M)o 18.2 ± 0.2 mag D 44± 4 Kpc MV-3.7 ± 0.6 mag μV 29.0 mag/arcsec-2 M/L 448±297 Belokurov et al. 2007

  25. Variable stars in Coma 2 RR Lyrae stars: 1 RRab, 1 RRc 1 SX Phe RRab <Pab> =0.67 d <Pc> =0.32 d RRc SX Phe BFOSC - Loiano 1.52 m Bologna Observatory Telescope WIRO-Prime - 2.3 m Wyoming Infrared Observatory INT – 2.5 Isaac Newton Telescope La Palma

  26. Variable stars in Coma µ0 = 18.02 mag D = 40 Kpc

  27. UMa II α(J2000) 08:51:30 δ (J2000) 63:07:48 Ellipticity 0.5 Rh 13′.6 Vtot(mag) 14.3 ± 0.5mag [Fe/H] -1.97 ± 0.15 (m-M)o 17.5 ± 0.3 mag D 32 +5/-4 Kpc MV-3.8 ± 0.6 mag μ V30.0 mag/arcsec-2 M/L 1722±1226 Zucker et al. 2006

  28. Variable stars in UMaII 1 RRab star BFOSC - Loiano 1.52 m Bologna Observatory Telescope LOWELL – 1.8 m Telescope WIRO-Prime - 2.3 m Wyoming Infrared Observatory <Pab> =0.66 d

  29. Variables in the SDSS dSph’s Oosterhoff II !!!!

  30. The SDSS new dSph’s in the Oosterhoff plane • Bootes • Canes Venatici I • Canes Venatici II • Coma • UMa II 15 RR Lyrae stars 48 “ 2 “ 2 “ 1 “ Oo II Oo Intermediate Oo II Oo II Oo II • 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. Summary

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