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Stellar archaeology in the Milky Way Halo

Stellar archaeology in the Milky Way Halo Variable stars and stellar populations in the new Milky Way satellites discovered by the SDSS. Ilaria Musella INAF – Osservatorio Astronomico di Capodimonte Napoli. Clementini , Dall’Ora, Marconi, Ripepi, Greco, Di Fabrizio,

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Stellar archaeology in the Milky Way Halo

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  1. Stellar archaeology in the Milky Way Halo Variable stars and stellar populations in the new Milky Way satellites discovered by the SDSS Ilaria Musella INAF – Osservatorio Astronomico di Capodimonte Napoli Clementini , Dall’Ora, Marconi, Ripepi, Greco, Di Fabrizio, Kinemuchi, Smith, Rodgers, Kuehn, Beers, Catelan, Pritzl

  2. Galaxy formation mechanisms • -CDM hierarchical scenario ---> dSphs as Building Blocks of • larger galaxies (such as the MW) • We should see remnants of this process • MW halo properties homogeneous with MW dSph satellites Many observational evidences of merging: • Sgr dSph • CMa dSph/overdensity (debated) • Substructures in the M31 halo

  3. new objects • Bootes • Bootes III • Ursa Major • Ursa Major II • Canes Venatici I • Canes Venatici II • Coma • Leo IV • Leo T • Hercules • Bootes II • Willman 1 • Segue 1 • Segue 2 • Koposov I • Koposov II Dwarf Spheroidal galaxies • Old dSph’s • Draco • Ursa Minor • Fornax • Carina • Sculptor • LeoI • LeoII • Sextans • Sagittarius • Canis Major The impact of SDSS has been dramatic: 16 new objects have been discovered in the last years. • The most numerous in the LG • The most dark matter dominated • Complex and unique SFH • Metallicity (chemistry) Problem • Variable Star Problem • Missing Satellite Problem (MSP)

  4. MW Inner 100 kpc

  5. Milky Way satellites Leo V Boo II Boo III

  6. new objects • Bootes • Bootes III • Ursa Major • Ursa Major II • Canes Venatici I • Canes Venatici II • Coma • Leo IV • Leo T • Hercules • Bootes II • Willman 1 • Segue 1 • Segue 2 • Koposov I • Koposov II Old dSph’s GCs And XV And XVI Luminosity --> And XI dSph’s BooIII And XII And XIII luminosity and mass limit of galaxy formation? …. or tidally disrupted remnants? Segue 2 SDSS dSph’s BooII K1 SDSS GCs GCs K2 Dimensions --> adapted from Belokurov et al. 2007

  7. New faint dwarf satellites: “building blocks” of the MW halo? • Fainter than previously known dSph’s: V > 28 mag/arcsec-2 • Properties intermediate between GCs and dSph’s (Mv ~ -7 mag, rh ≥ 100 pc) • Darkest known stellar systems (M/L from ~35 to ~1000) • Metal poor (…as metal poor as stars in the MW halo) • Irregular shape  distorted  tidally interacting • Host an ancient population (t ~ 13 gyr) RR Lyrae • Satellite deficit reduced to a factor 4 (Simon & Geha, 2007)

  8. Oo II Gap Oo I Looking for the “building blocks” of the MW halo In the MW, most of the GCs with an RR population sharply divide into two distinct groups, based on <Pab> (Oosterhoff 1939) Oo I <Pab> = 0.55 d OoII <Pab> = 0.65 d And outside the Milky Way? And the old dSphs? Oo II Gap Oo I adapted from Catelan, Greco et al. 2009, in preparation

  9. Our projects: Which is the Oostehoff type of SDSS faint dSphs? We use time-series photometry for the listed galaxy to study the properties of their variable stars • In progress • UMa II • Hercules • Bootes II • To observe • Bootes III • Published • Bootes I • Canes Venatici I • Canes Venatici II • Coma • Accepted • Leo IV Telescope time: 1.5m Loiano, 1.8m Lowell, 2.2m ESO,WIRO, INT, TNG,SOAR, WHT

  10. Variable stars in the new SDSS dSph’s α(J2000) 14:00:06 δ(J2000) 14:30:00 Ellipticity0.33 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 revised 19.11 ± 0.08 mag D 60 ±6kpc revised 66 ±6kpc MV -5.8± 0.5 mag μV28.3± 0.5 mag/arcsec-2 M/L 130-680 …alongwith the UMidSphoneof the most dark matterdominatedobject in the Universe! Belokurovet al. 2006 Dall’Ora et al. 2006, ApJL • 11 RR Lyrae stars: • 5 RRab’s, 5 RRc’s, • 1 RRd, 1 LPV • <Pab> =0.69 d • <Pc> =0.37 d • OoII

  11. Variable stars in the new SDSS dSph’s • RRab’s • RRc • AC α(J2000) 13:28:03 δ(J2000) 33:33:21.0 Ellipticity0.38 Rh8′.5±0′.5 Vtot(mag) 13.9 ± 0.5 mag [Fe/H] -2.09 ± 0.02 (m-M)o 21.75 ± 0.2mag revised 21.62 ± 0.06 mag D 224 +22/-20kpc revised 210 +7/-5 kpc MV -7.9± 0.5 mag μV28.2± 0.5 mag/arcsec-2 M/L 221 ±108 Zuckeret al. 2006 Kuehnet al. 2008, ApJL [Fe/H] = -2.1/-2.0 (ZW84/CG97) • 4 Age Components • 13 Gyr (red line) • 5 Gyr (blue line) • 1.5 Gyr (green line) • 0.6 Gyr (black line) • 23 RR Lyrae stars: • 18 RRab’s, 5 RRc’s • 3AC • 58 candidate variable (RR Lyrae?) • <Pab> =0.60 d • <Pc> =0.38 d • Oosterhoff intermediate • Variable Stars • RRab (in red) • RRc (in blue) • Candidate AC (in purple) • Variables without periods (in cyan)

  12. Variable stars in the new SDSS dSph’s • RRab • RRc α(J2000) 12:57:10 δ(J2000) 34:19:15 Ellipticity0.3 Rh3′.0 Vtot(mag) 15.1 ± 0.5 mag [Fe/H] -2.31 ± 0.12 (m-M)o 20.09 ± 0.2mag revised 21.02 ± 0.06 mag D 151 +15/-13kpc revised 160 +4/-5 kpc MV -4.8± 0.6 mag μV29.5mag/arcsec-2 M/L 336 ±240 Belokurovet al. 2007 Greco et al. 2008, ApJL • 2 RR Lyrae stars: • 1 RRab, 1 RRc • Several candidate BSSs • <Pab> =0.74 d • <Pc> =0.36 d • OoII __ M15 _ _ M3

  13. Variable stars in the new SDSS dSph’s __ M68 _ _ M3 α(J2000) 12:26:59 δ(J2000) 23:54:15 Ellipticity0.5 Rh 5’ Vtot(mag) 15.1 ± 0.5 mag [Fe/H] -2.00 ± 0.07 (m-M)o 18.2 ± 0.2mag revised 18.02 ± 0.06 mag D 44 ±4kpc revised 40 ±1kpc MV -3.7± 0.6 mag μV29.0mag/arcsec-2 M/L 448 ±297 Belokurovet al. 2007 Musellaet al. 2009, ApJL • 2 RR Lyrae stars: • V1= RRab, V2= RRc, • V3=short period variable • <Pab> =0.67 d • <Pc> =0.32 d • OoII

  14. Variable stars in the new SDSS dSph’s α(J2000) 11:32:57 δ(J2000) -00:32:00 Ellipticity0.25 Rh 3’.3 Vtot(mag) 15.9 ± 0.5 mag [Fe/H] -2.31 ± 0.10 (m-M)o 21.0 ± 0.2mag revised 20.94 ± 0.07 mag D 158 +15/-14 kpc revised 154 ±5kpc MV -5.1± 0.6 mag μV28.3mag/arcsec-2 M/L 151 ±177 Belokurovet al. 2007 Moretti et al. 2009, ApJL, accepted __ M15 • 3 RR Lyrae stars: • 3 RRab’s • 1 SX Phoenicis (V4) • <Pab> =0.66 d • OoII A Pair with Leo V? (Koch et al. 2008)

  15. Variable stars in the new SDSS dSph’s α(J2000) 16:31:02 δ(J2000) 12:47:30 Ellipticity0.5 Rh 8’.0 Vtot(mag) 14.7 ± 0.5 mag [Fe/H] -2.27 ± 0.07 (m-M)o 20.7 ± 0.2mag D 138 +13/-12 kpc MV -6.0± 0.6 mag μV30.0mag/arcsec-2 M/L 332 ±221 Belokurovet al. 2007 Work in progress

  16. Variable stars in the new SDSS dSph’s α(J2000) 13:58:00 δ(J2000) 12:51:00 Ellipticity 0.21± 0.21 Rh 4’.1± 1.6 Vtot(mag) …. [Fe/H] -1.8 (m-M)o 18.1 ± 0.4mag D 60 ± 10kpc revised 42 ±8kpc MV -3.1± 1.1 mag revised -2.4 (-2.7) ± 0.7 (1.0) mag μV29.8mag/arcsec-2 revised 28.4 mag/arcsec-2 M/L~ 35 Wash et al. 2006, Wash et al. 2007 (confirmeddSph), Wash et al. 2009, Kocket al. 2008 (remnant in Sgrstream). Notclear nature Work in progress

  17. Variable stars in the new SDSS dSph’s 1 Rrab <Pab> =0.66 d OoII α(J2000) 08:51:30 δ(J2000) 63:07:48 Ellipticity0.5 Rh 13’.6 Vtot(mag) 14.3 ± 0.5 mag [Fe/H] -1.97 ± 0.15 (m-M)o 17.5 ± 0.3mag D 32 +5/-4 kpc MV -3.8± 0.6 mag μV30.0mag/arcsec-2 M/L 1722 ± 1226 Zuckeret al. 2006 Work in progress

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

  19. The SDSS new dSph’s in the Oosterhoff plane Oo II Gap Oo I

  20. Thank you

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