1. 1 / 17 The Elemental Abundance Distributions of Milky Way Satellite Galaxies Evan Kirby (HF09) Caltech Small Magellanic Cloud, HST/ACS credit: NASA, ESA, and A. Nota (STScI/ESA)

2. 2 / 17 in collusion with... Mike Bolte (HF90) Judy Cohen Anna Frebel Marla Geha (HF03) Raja Guhathakurta (HF92) Bob Kraft Steve Majewski (HF92) Connie Rockosi (HF01) Michael Siegel Josh Simon Tony Sohn Chris Sneden

3. 3 / 17 Milky Way halo probably consists of dissolved dwarf satellites Chemical abundances in satellites that survive today don't look like chemical abundances in the halo What causes the differences? Evolution of the Milky Way Johnston et al. (2008) ApJ 689, 936 Venn et al. (2004) ApJ 128, 1177 [Mg/Fe] [Ca/Fe] [Ti/Fe] [Mg+Ca+Ti/3Fe] [Fe/H] Venn & Hill (2008) ESO Messenger 134, 23 [Ca/Fe] [Fe/H]

4. 4 / 17 rest wavelength (Å) residual flux observed synthetic [α/Fe] = 0.0 observed synthetic [α/Fe] = +0.3 Method to Collect a Bunch of Abundances in dSphs Keck + DEIMOS

5. 5 / 17 Accuracy of [Fe/H]

6. 6 / 17 Accuracy of [X/Fe]

7. 7 / 17 Overview of Galactic Chemical Evolution Pagel (1992) IAU Symp., Stellar Populations of Galaxies halo metallicity distribution: [Fe/H] [O/H] Δ N Pagel (1992) IAU Symp., Stellar Populations of Galaxies within the solar cylinder (G dwarf problem): [Fe/H] [O/H] Δ N

8. 8 / 17 Metallicity Distributions EK et al. (2009) ApJ 705, 328 Frebel, EK, & Simon (2010) Nature 464, 72. Uranologists have detected a relic from the former universe – a star that may have been among the second generation of stars to form subsequently the Big Bang. … The team suspected that the methods used to find metal-poor stars in midget galaxies were colored in a way that caused the surveys to miss the most metal- poor stars. Team member Evan Kirby, a Caltech uranologist, highly-developed a method to estimate the metal copiousnesss of large numbers of stars at a time, making it possible to expeditiously search for the most metal-poor stars in midget galaxies. ––– http://science.knopok.net/?p=221 Uranologists have detected a relic from the former universe – a star that may have been among the second generation of stars to form subsequently the Big Bang. … The team suspected that the methods used to find metal-poor stars in midget galaxies were colored in a way that caused the surveys to miss the most metal- poor stars. Team member Evan Kirby, a Caltech uranologist, highly-developed a method to estimate the metal copiousnesss of large numbers of stars at a time, making it possible to expeditiously search for the most metal-poor stars in midget galaxies. ––– http://science.knopok.net/?p=221

9. 9 / 17 Metallicity-Luminosity Relation

10. 10 / 17 Metallicity Spread vs. Luminosity

11. 11 / 17 Radial Gradients

12. 12 / 17 Alpha Elements: Star Formation Timescales [Fe/H] [O/Fe] burst continuous burst quiescent bursts continuous superimposed burst Gilmore & Wyse (1991) ApJL 367, L55

13. 13 / 17 Fornax age (Gyr) [M/H] SFR ( M ʘ Myr -1 ) Dolphin et al. (2005) arXiv:astro-ph/0506430 [Mg/Fe] [Si/Fe] [Ca/Fe] [Ti/Fe] [ α /Fe] [Fe/H]

14. 14 / 17 Sculptor age (Gyr) [M/H] Dolphin et al. (2005) arXiv:astro-ph/0506430 [Fe/H] [Mg/Fe] [Si/Fe] [Ca/Fe] [Ti/Fe] [ α /Fe] SFR ( M ʘ Myr -1 )

15. 15 / 17 Draco age (Gyr) [M/H] SFR Grebel (1998) Moriond Astrophysics Meeting, Dwarf Galaxies and Cosmology [Fe/H] [Mg/Fe] [Si/Fe] [Ca/Fe] [Ti/Fe] [ α /Fe]

16. 16 / 17 Trends of Alpha Elements [Fe/H] [Mg/Fe] [Si/Fe] [Ca/Fe] [Ti/Fe] [ α /Fe]

17. 17 / 17 Conclusions Abundances trends with increasing luminosity:  Larger ‹[Fe/H]›  Larger σ(Z/Z ʘ )  More gas infall  Flatter [α/Fe] at high [Fe/H] Mass or redshift of infall into Milky Way gravitational potential may determine star formation history

18. 18 / 17 Hypothesis: Infall Redshift Bullock et al. (2009) ApJ, submitted, arXiv:0912.1873