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Finding & Using BHB Stars to Investigate Galactic Halo Dynamics

Peter Mares Cornell University REU CTIO 2008 Mentors: Roberto de Propris and Craig Harrison. Finding & Using BHB Stars to Investigate Galactic Halo Dynamics. What are BHB Stars?. Blue Horizontal Branch Stars A-type stars Post MS and Red Giant Constant luminosity Distance indicators

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Finding & Using BHB Stars to Investigate Galactic Halo Dynamics

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  1. Peter Mares Cornell University REU CTIO 2008 Mentors: Roberto de Propris and Craig Harrison Finding & Using BHB Stars to Investigate Galactic Halo Dynamics

  2. What are BHB Stars? • Blue Horizontal Branch Stars • A-type stars • Post MS and Red Giant • Constant luminosity • Distance indicators • A-type contaminates • MS stars • Blue Straggler (BS) stars

  3. The 2df QSO Redshift Survey • 2QZ Survey • Anglo-Australian Obs. • Color range • Two 75° by 5° strips • 16<bJ<20.85

  4. Using the 2QZ Database and Object Counts • “Star”...13444 • White Dwarfs, Cataclysmic Variables, Dwarf Binary Systems...9576 • No Spectra?...9341 • Inaccurate Radial Velocities...8931 • Bad spectra...2153 • 666 Stars fitting criteria

  5. Radial Velocity Corrections • Determining Radial Velocities • SDSS templates • Our spectra as templates • U. Munari (2005) synthetic templates

  6. BHB Selections • Identification of BHB stars vs. Blue Straggler stars • Measure width of Hδ and Hγ lines at 80% (Yanny 2000)‏ • Surface gravity of candidate stars • Unsuccessful attempt to use L. Clewley (2004) identification method • Convolution of Sersic profile fit and Gaussian • D0.15—color • Scale-width—shape methods (b-c)

  7. The Catalog • Positions (x,y,z) • Motion (Proper Motion, Radial Velocity) • Colors • Apparent magnitude bJ • u-bJ • bJ-r • 80% widths of Balmer Lines (Hδ and Hγ)

  8. R.A. vs Distance of our BHB Stars

  9. Galactic Latitude b vs Distance

  10. G.L. b vs u-bJ of our BHB Stars

  11. Future Work with the Catalog • Catalog work • Formation of the phase space • Metallicity measurements • More error calculations • Possible uses of the catalog • Stellar population studies • Stellar groups or streams • Curvature and Shape of the Halo • Mass of the Halo & the Milky Way

  12. Thank You!! • Craig and Roberto • CTIO • NSF REU grant

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