STELLARSTELLAR ARCHEOLOGY:ARCHEOLOGY: What White Dwarf Stars Tell Us About the History of the Galaxy Dr.Dr. TerryTerry D.D. OswaltOswalt Department of Physics & Space Sciences Florida Institute of Technology [email protected] “Stars, Companions and Their Interactions: A Memorial to Robert H. Koch” Villanova University, Villanova PA, August 10, 2011 Current Collaborators Florida Tech Jingkun Zhao Tomomi Otani, Perry Bird, Matthew Bourque, Andrew Colson, Beverly Watson U. Arizona Jay Holberg Austin Peay St. U. J. Allyn Smith Iowa St. U. Lee Ann Willson, Qian Wang National Astronomical Observatories of China A-li Luo, Gang Zhao Villanova U. Ed Guinan, Ed Sion U. Washington Nicole Silvestri National Science Foundation AST-0807919 WhiteWhite DwarfDwarf StarsStars End product of stellar evolution star formation history mass recycling Test of general relativity mass-radius relation gravitational redshifts, masses Galactic structure thick/thin disk, halo dark matter content Cosmology age of Galaxy & Universe supernovae & dark energy To find WDs look for faint, fast-moving objects Bright & Slow Faint & Fast H m + 5 log + 5 faint,faint, nearbynearby objectsobjects blue (hot) red (cool) ““FragileFragile”” Binaries:Binaries: DefinitionDefinition “…small galactic clusters containing stars of the same age and composition.” –Greenstein 1986 Giclas et al. 1971-8 Luyten 1969 et seq. Most common type of binary? (6124 found by Luyten) Common proper motion, no detectible orbital motion Coeval, (barely) gravitationally-bound components MS+MSMS+MS PairsPairs Oswalt 1997 Zinnecker 1984 Different formation mechanisms? Close: fragmentation vs. fission Wide: capture vs. disintegration Main sequence pairs (>6000 known) Most common type of binaries in Disk? Halo? Sensitive to long-term Galactic perturbations See Allen, Chanamé, Gavras, Kiyaeva, Poveda 2006; New surveys: Chanamé & Gould 2004, Lépine & Shara 2005 MS+WDMS+WD PairsPairs Oswalt & Sion 1988 WD MS LP208-32 A/B Binaries with at least one evolved star (>1000 known) MS “benchmark” for Vr , UVW, metallicity WD “benchmark” for age Test of post-MS mass loss & orbit evolution WD initial-final mass relation (IFMR) See Johnston, Catalan 2006 OrbitsOrbits -- comparisonscomparisons Johnston 2006 Disrupted pairs BH+MS or NS+MS disrupted? Oswalt 1994 <MWD> Orbit evolution can only explain ~ 1/2 the increases seen Incompleteness? Lower SFR, especially recently? Wider a(to) for high mass binaries? www.saraobservatory.org SARA-N 1.0-m Kitt Peak, Arizona + + FIT Ortega 0.8-m Melbourne, FL SARA-S 0.6-m Cerro Tololo - Chile + AsterosiesmologyAsterosiesmology Otani 2011 l=1 m=+1 l=3 m=+2 l=3 m=+3 l=2 i=45º DetectingDetecting aa PlanetaryPlanetary ““SurvivorSurvivor””:: V391V391 PegasiPegasi bb Silvotti et al. 2007 SARA-S El Pachón 2MASS Dorm Admin Blanco 4m TheBlanco view 4 -frommeter the telescope top Cerro Tololo, Chile “By means of Telescopes, there is nothing so far distant but may be represented to our view…” Robert Hooke 1665 FirstFirst SpectraSpectra ofof CoolCool OldOld WhiteWhite DwarfsDwarfs 1 Gyr = 1,000,000,000 yr 2.2 Gyr 3.0 Gyr Hintzen et al. 1989 8.1 Gyr 7.6 Gyr HowHow CommonCommon areare WhiteWhite Dwarfs?Dwarfs? HowHow OldOld isis thethe Galaxy?Galaxy? 20 pc WD Sample 3.0 2.5 y = 3x - 1.5075 R2 = 1 2.0 1.5 1.0 log N(cumulative) y = 2.568x - 1.2474 0.5 R2 = 0.9971 0.0 (stars per cubic parsec) 0.4 0.6 0.8 1.0 1.2 log d (pc) 126 WDs within 20 pc Sample complete to 4pc Oswalt et al. 1996: 9.5 ±1.0 Gyr (N=50) 7.4 ± 0.7 x 10-3 pc-3 Smith 1997: 9.4 ±0.5 Gyr (N=166) →135 pc3 for 1 WD Holberg, Oswalt & Sion 2011 bright faint WDWD MASSES:MASSES: GravitationalGravitational RedshiftsRedshifts Vorb < 1 km/s Vrs ≈ Vrad(WD) – Vrad(MS) Vrs ~ M / R Bergeron et al. Vrs ~ M/R Silvestri et al. < Mergers? Silvestri et al. 2001 DarkDark MatterMatter Optical (blue) + X-ray (pink) Markevitch et al. 2006, Clowe et al., 2006 1E0657-56 “Bullet Cluster” Fritz Zwicky Vera Rubin 1898 - 1974 1928 - ““CoolCool BlueBlue WDsWDs”” Sauman & Jabobsen 1999 (brightness) Hodgkin et al. 2000 WD0346+246 Age ~ 12 Gyr wavelength WhiteWhite DwarfsDwarfs && DarkDark MatterMatter -- NOTNOT Silvestri, Oswalt, Hawley 2002 halo Scatter in Velocity anticenter velocity anticenter halo disk U V forward velocity StellarStellar ActivityActivity www.mtwilson.edu/hk/overview CaII K H K S HK R V R V StellarStellar ActivityActivity vs.vs. AgeAge Zhao et al. 2011a Skumanich 1972 H K S HK R V Activity Like people, stars get less active as they get older! Mass ChromosphericChromospheric ActivityActivity inin MSMS BinariesBinaries Testing the assumption of coevality using SDSS pairs Zhao et al. 2011c, in prep 2 Gyr 4 Gyr 8 Gyr MotherMother NatureNature recyclesrecycles……wewe’’rere proof!proof! The WD Initial-to-Final Mass Relation NGC 2440 Zhao et al. 2011b, in prep WD progenitor life → original mass Mi TTeff && loglog gg ofof WhiteWhite DwarfDwarf inin aa BinaryBinary tt cool == ttms –– ttprog ((ttprog MMi forfor WD)WD) CD-38 10983 Koester 2010 models InitialInitial--FinalFinal MassMass RelationRelation (IMFR)(IMFR) ofof WhiteWhite DwarfsDwarfs inin FragileFragile BinariesBinaries Zhao et al. 2011b, in prep MetallicityMetallicity ofof MainMain SequenceSequence StarsStars inin FragileFragile BinariesBinaries σ[Fe/H]=0.15 dex compared with the values from high resolution spectra Zhao et al. 2011a 40 EriA Maximum Correlation with theoretical spectra library of Castelli & Kurucz 2003 Post Main Sequence Pulsations & Mass Loss “death line” Willson & Wang 2011 D. Porter, S. Anderson, P. Woodward U. Minnesota V. Wilkat, FIT/SARA MetallicityMetallicity andand PostPost--MSMS MassMass LossLoss Solar metallicity stars (blue) lose more mass than lower metallicity stars (red) because: (1) dM/dt reaches a critical value at lower luminosity, hence smaller core and more envelope to lose (2) More dust, higher Willson & Wang 2011 opacity, stronger wind MetallicityMetallicity andand thethe IFMRIFMR Zhao et al. 2011b, in prep GyrochronologyGyrochronology (Bird, Watson summer 2011 REU; Guinan et al. 2011) Barnes 2008 Pizzolato et al. 2003 OngoingOngoing WorkWork…… CACA vs.vs. ageage relationrelation inin WD+MSWD+MS binariesbinaries DeterminationDetermination ofof RotationRotation AgesAges OrbitOrbit evolutionevolution andand massmass lossloss ImprovingImproving thethe WDLFWDLF && IFMR,IFMR, e.g.e.g. [Fe/H][Fe/H] SearchSearch forfor fragilefragile binariesbinaries inin halohalo VariabilityVariability inin coolestcoolest WDsWDs HighHigh precisionprecision VVr mm1 && mm2 Support from U.S. National Science Foundation grant AST- 0807919 and NSF (China) grants 11078019 and 10821061 is gratefully acknowledged ThankThank--you!you! “I don’t pretend to understand the Universe—it’s a great deal bigger than I am.” Thomas Carlyle 1868.