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Jason Kalirai (STScI)

Diamonds in the Rough: The Oldest Stars in the Galaxy. June 11 th , 2009 - 1. Space Telescope Science Institute: Hubble Science Briefings. Jason Kalirai (STScI). Outline An Introduction: The First Hints on How Stars Evolve. Our Current Picture of Stellar Evolution

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Jason Kalirai (STScI)

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  1. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 1 Space Telescope Science Institute: Hubble Science Briefings Jason Kalirai (STScI) Outline An Introduction: The First Hints on How Stars Evolve. Our Current Picture of Stellar Evolution A Surprise in our Backyard: The First “Discovered” White Dwarf Why Search for Dead Stars? What 120 orbits of Hubble Space Telescope Time Gets You. Summary and Future Outlook

  2. June 11th, 2009 - 2 Space Telescope Science Institute: Hubble Science Briefings An Interesting Correlation: The Hertzsprung-Russell Diagram Ejnar Hertzsprung (1905) Parallax:Parallax angle = 1 / (distance to star) Observation: 1.) Stars with the same parallax have different luminosities. Giants vs Dwarfs! First luminosity classes created. 2.) Luminosities of some stars are correlated with their colors…

  3. Luminosity Temperature June 11th, 2009 - 3 Space Telescope Science Institute: Hubble Science Briefings An Interesting Correlation: The Hertzsprung-Russell Diagram Ejnar Hertzsprung Henry Norris Russell Publ. Astrophys. Observ. Potsdam 22, 1, 1911 The Observatory, Vol. 36, 324, 1913

  4. “Zur Strahlung der Sterne” (On the Luminosity of the Stars) - Hertzsprung, E., Zeitschrift fur Wissenschaftliche Photographie (Journal for Scientific Photography), Vol. 3, 442, 1905 - Hertzsprung, E., Publ. Astrophys. Observ. Potsdam, Vol. 22, 1, 1911 “Giant and Dwarf Stars” - Russell, H. N., The Observatory, Vol. 36, 324, 1913 “On the Probable Order of Stellar Evolution” - Russell, H. N., The Observatory, Vol. 37, 165, 1914 “…one corner of the diagram is vacant…There do not seem to be any faint white stars. All of the very faint stars are very red.” “…the converse propositions are not true; there is no doubt at all that there exist many very bright red stars (such as Arcturus, Aldebaran, Antares, etc.).” “There appears, from the rather scanty evidence at present available, to be some correlation between mass and luminosity.” Luminosity Temperature June 11th, 2009 - 3a Space Telescope Science Institute: Hubble Science Briefings An Interesting Correlation: The Hertzsprung-Russell Diagram Ejnar Hertzsprung Henry Norris Russell Publ. Astrophys. Observ. Potsdam 22, 1, 1911 The Observatory, Vol. 36, 324, 1913

  5. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 4 Space Telescope Science Institute: Hubble Science Briefings Two Key Properties 1.) Star formation produces predominantly low mass stars. 2.) Stellar evolution depends primarily on mass.

  6. June 11th, 2009 - 5 Space Telescope Science Institute: Hubble Science Briefings

  7. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 6 Space Telescope Science Institute: Hubble Science Briefings - Sirius: brightest star in the night sky (V = -1.5). - 1840’s - exhibits irregular motions on the sky (Bessel 1844). - Optical detection of companion by Alvan Clark in 1862.

  8. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 7 Space Telescope Science Institute: Hubble Science Briefings - 50 year binary orbit 1 Msun companion, but MV = 11.3 (0.003 Lsun)! - Sirius A and B have similar colors Radius of Sirius B = 1/100 Sirius A. - Adams (1914; 1925): spectrum is white, gravitational redshift measured. - White dwarf: very dense remnant of a hydrogen burning star (no fuel).

  9. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 8 Space Telescope Science Institute: Hubble Science Briefings White Dwarf Fact Sheet Composition: Carbon core under extreme pressure….a diamond! Golden Jubilee Diamond VS Average White Dwarf Discovery: 1985 1862 Size: 5 cm 1,000,000,000 cm Mass: 0.1 kg 1 X 1030 kg Density: 5 g/cm3 1,000,000 g/cm3 Value: >10 million USD -----------------

  10. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 8a Space Telescope Science Institute: Hubble Science Briefings White Dwarf Fact Sheet Composition: Carbon core under extreme pressure….a diamond! Golden Jubilee Diamond VS Average White Dwarf Discovery: 1985 1862 Size: 5 cm 1,000,000,000 cm Mass: 0.1 kg 1 X 1030 kg Density: 5 g/cm3 1,000,000 g/cm3 Value: >10 million USD ----------------- Finders Fee:$$$$$ <<10 million USD

  11. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 9 Space Telescope Science Institute: Hubble Science Briefings A Few Reasons to Study White Dwarfs 1.) Over 97% of all stars will eventually form white dwarfs. Unique link to the distribution of first generation stars in old stellar populations. 2.) White dwarfs cool predictably with time use as chronometers. 3.) Upper mass limit to white dwarf production = lower limit to type II SNe. 4.) Constraining fundamental stellar evolution and stellar mass loss. 5.) Theoretical calibration of evolutionary models of AGB and PN phases.

  12. Diamonds in the Rough: The Oldest Stars in the Galaxy Open Star Clusters (Intermediate age) 1000’s of stars Globular Star Clusters (old and rich) 100,000’s of stars Stellar Associations (young and sparse) 10’s of stars June 11th, 2009 - 10 Space Telescope Science Institute: Hubble Science Briefings How Do We Find These Gems? Should be faint and blue. Search rich stellar populations.

  13. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 11 Space Telescope Science Institute: Hubble Science Briefings White Dwarfs in Globular Clusters? Buonanno et al. (1994, A&A, 290, 69)

  14. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 12 Space Telescope Science Institute: Hubble Science Briefings Ultra-deep HST Imaging of the Nearest Clusters Measure the ages of nearby globular clusters using white dwarf cooling theory. 1st study - Messier 4 - 123 orbits of HST/WFPC2 awarded in Cycle 9. 2nd study - NGC 6397 - 126 orbits of HST/ACS awarded in Cycle 13. 3rd study - 47 Tuc - 121 orbits of HST/ACS and WFC3 to be executed in Cycle 17. Hansen et al. (2007, ApJ, 671, 380)

  15. Kalirai et al. (2008, ApJL, 682, 37)

  16. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 16 Space Telescope Science Institute: Hubble Science Briefings The Age of the MW Halo NGC 6397 126 HST/ACS orbits Richer et al. (2006, Science, 313, 936) Hansen et al. (2007, ApJ, 671, 380)

  17. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 -16a Space Telescope Science Institute: Hubble Science Briefings The Age of the MW Halo NGC 6397 126 HST/ACS orbits Kalirai et al. (2007, ApJL, 657, 93) Richer et al. (2006, Science, 313, 936) Hansen et al. (2007, ApJ, 671, 380)

  18. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 -16b Space Telescope Science Institute: Hubble Science Briefings The Age of the MW Halo NGC 6397 126 HST/ACS orbits Kalirai et al. (2007, ApJL, 657, 93) Richer et al. (2006, Science, 313, 936) Hansen et al. (2007, ApJ, 671, 380)

  19. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 -16c Space Telescope Science Institute: Hubble Science Briefings The Age of the MW Halo NGC 6397 126 HST/ACS orbits Kalirai et al. (2007, ApJL, 657, 93) Richer et al. (2006, Science, 313, 936) Hansen et al. (2007, ApJ, 671, 380)

  20. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 17 Space Telescope Science Institute: Hubble Science Briefings Signature of a White Dwarf

  21. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 -17a Space Telescope Science Institute: Hubble Science Briefings Signature of a White Dwarf

  22. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 -17b Space Telescope Science Institute: Hubble Science Briefings Signature of a White Dwarf

  23. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 18 Space Telescope Science Institute: Hubble Science Briefings Signature of a White Dwarf NGC 6397 Richer et al. (2006, Science, 313, 936) Kalirai et al. (2007, ApJL, 657, 93) Kalirai et al. (2009, ApJ, submitted)

  24. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 19 Space Telescope Science Institute: Hubble Science Briefings Dating the Oldest Stars NGC 6397 126 HST/ACS orbits Hansen et al. (2007, ApJ, 671, 380) Conclusions: The Luminosity and Age of the Faintest White Dwarfs 1.) These white dwarfs are more than 1 billion times fainter than the faintest stars seen with the naked eye! 2.) The first stars formed in our Galaxy 12 Gyr ago, 1.7 Gyr after the Big Bang. 3.) The disk of our Galaxy formed much later, 8 Gyr ago.

  25. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 20 Space Telescope Science Institute: Hubble Science Briefings WDs in Globular Clusters: >400 HST orbits! NGC 6397 126 HST/ACS orbits Kalirai et al. (2009, ApJ, submitted)

  26. June 11th, 2009 - 21 Space Telescope Science Institute: Hubble Science Briefings The End!

  27. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 22 Space Telescope Science Institute: Hubble Science Briefings The Age of the MW Disk White dwarf mass function: Liebert, Bergeron & Holberg (2005)

  28. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 23 Space Telescope Science Institute: Hubble Science Briefings Summary of Globular Cluster Work: White dwarf cooling age of NGC 6397 = 11.5-12.0 Gyr (t = 10.1-12.5 for M4). NGC 6397: = +3.56 +/- 0.04 mas/yr, = -17.34 +/- 0.04 mas/yr. Cluster orbit suggests frequent interactions with bulge/disk. Proper motion cleaned study of low mass cluster mass function. z = 0.1 extragalactic globular cluster system found. …and Open Cluster Work: age/distance/reddening/binary fraction/etc… measured for a large sample. Mfinal = (0.109 +/- 0.007)Minitial + (0.394 +/- 0.025) Msun. Age of Galactic disk = 8 Gyr, Age of Galactic halo = 12 Gyr. Mass loss is more efficient in higher metallicity environments. NGC 6791 stars evolved along three channels…no age issue, 2nd peak.

  29. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 24 Space Telescope Science Institute: Hubble Science Briefings Some CFHT CMDs

  30. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 - 25 Space Telescope Science Institute: Hubble Science Briefings Kalirai et al. (2008, ApJ, 676, 594) Weidemann + Reimers & Koester (1980’s) Claver et al. (2001) Dobbie et al. (2004, 2006) Williams et al. (2004, 2007) Kalirai et al. (2005) Liebert et al. (2005) Kalirai et al. (2008, ApJ, 676, 594)

  31. Diamonds in the Rough: The Oldest Stars in the Galaxy June 11th, 2009 -25a Space Telescope Science Institute: Hubble Science Briefings Kalirai et al. (2008, ApJ, 676, 594) Weidemann + Reimers & Koester (1980’s) Claver et al. (2001) Dobbie et al. (2004, 2006) Williams et al. (2004, 2007) Kalirai et al. (2005) Liebert et al. (2005) Kalirai et al. (2008, ApJ, 676, 594)

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