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Connection between Abundances in the Intergalactic Medium and Metal-Poor Galactic Halo Stars

Connection between Abundances in the Intergalactic Medium and Metal-Poor Galactic Halo Stars. Yong-Zhong Qian University of Minnesota November 28, 2005 Qian 2005, ApJL, submitted. Metals in the IGM. Lognormal distribution (Schaye et al. 2003). Metals in the IGM (Continued).

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Connection between Abundances in the Intergalactic Medium and Metal-Poor Galactic Halo Stars

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  1. Connection between Abundances in the Intergalactic Medium and Metal-Poor Galactic Halo Stars Yong-Zhong Qian University of MinnesotaNovember 28, 2005 Qian 2005, ApJL, submitted

  2. Metals in the IGM Lognormal distribution (Schaye et al. 2003)

  3. Metals in the IGM (Continued) • No evolution over pregalactic outflowsprovided the inventory by z~4 • Fixed Si/C and C/O ratios (Aguirre et al. 2004; Simcoe et al. 2004) well-defined composition due to extensive mixing of pregalactic outflows

  4. Metals in Galactic Halo Stars Enrichment by a single Fe-producing SN II Hydrostatic burning: C, N, O, …, Na, Mg, Al; Explosive burning: Si, …, Ca, Sc, Ti, …, Fe, … Zn Expectation: widely-varying ratios at [Fe/H] < -2.3

  5. Metals in Galactic Halo stars (Continued) Observed: regular pattern from Na to Zn over -4 < [Fe/H] < -2.5 (e.g., Cayrel et al. 2004; Cohen et al. 2004) Proposed explanation: formed at z < 4 but before local SNe II occurred to produce Na to Zn inherited well-defined composition of IGM

  6. Tests of the Connection • Only C, O, Si measured in the IGM • Complications for comparison of C/O and Si/C in the IGM and halo stars Modification of stellar C abundance: internal mixing (dredge-up) and external contamination (AGB companion) Uncertainties in stellar O abundance: [OI] line sensitive to granulation in atmosphere (3-D models required)

  7. Tests of the Connection (Continued) Fixed C/Fe in the IGM lognormal distribution of (Fe/H) 17 unmixed & uncontaminated stars (Spite et al. 2005)

  8. 253 stars from Barklem et al. (2005)

  9. Effect of scatter in [C/Fe] on the metallicity distribution? Not any if due to internal mixing or external contamination after birth

  10. 119 stars with 0 < [C/Fe] < 0.4

  11. Effect of scatter in [Neutron Capture/Fe] on the metallicity distribution? Not any if due to external contamination after birth or pre-enrichment by sources that do not produce Na to Zn

  12. Hill et al. (2002); Westin et al. (2000) CS 31082-001 HD115444HD122563

  13. 127 stars with -0.2 < [Sr/Fe] < 0.2

  14. The Big Picture • Pregalactic outflows provided IGM with a well-mixed inventory of metals by z~4 • Lognormal metallicity distribution of IGM (mean and scatter depend on density) • Halo stars with [Fe/H] < -2.3 formed out of infalling gas from IGM before local SNe II occurred to produce Na to Zn

  15. The Big Picture (Continued) • Halo stars with [Fe/H] < -2.3 have regular pattern from Na to Zn and their metallicity distribution follows that of IGM • Scatter in [C/Fe] due to internal mixing or external contamination after birth • Scatter in [Neutron Capture/Fe] due to external contamination after birth or pre-enrichment by sources that do not produce Na to Zn

  16. The Big Picture (Continued) • At [Fe/H] ~ -2.3, regular SNe II that produce Na to Zn start to increase their abundances in the ISM beyond the IGM inventory • Metallicity distribution of halo stars with [Fe/H] > -2.3 depend on star formation history in the halo, whereas that for [Fe/H] < -2.3 is determined by IGM

  17. Future Tests • Measurements of C/O and Si/C in IGM: sensitivity to UV background model[C/O] ~ -0.5 to 0 (Simcoe et al. 2004) [Si/C] ~ 0.4 to 0.7 (Aguirre et al. 2004) • Measurements in 17 unmixed metal-poor stars: uncertainties in O and Si [C/O] ~ -0.5 to 0, [Si/C] ~ -0.2 to 0.8 (Cayrel et al. 2004; Spite et al. 2005)

  18. Importance of [Si/C] • VMS ( ): [Si/C]=1.18 (Heger & Woosley 2002) • SNe II ( ): [Si/C]=0.42 (Woosley & Weaver 1995) ~50% of the Si from VMS (Qian & Wasserburg 2005a)

  19. Massive Black Holes (MBH) from VMS (Qian & Wasserburg 2005b) • VMS of produce pair instability SN (PI-SN) • VMS of higher masses produce MBH (Heger & Woosley 2002)

  20. Relation to SuperMassive BH • Baryonic mass fraction of SMBH (e.g., Marconi et al. 2004) • MBHSMBH ( ) (Madau & Rees 2001) >10% of SMBH from MBH mergers (Islam et al. 2004)

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