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Dissecting the Red Sequence: Star Formation Histories & Mass to Light Ratios

Dissecting the Red Sequence: Star Formation Histories & Mass to Light Ratios. Genevieve J. Graves University of California, Santa Cruz with Sandra Faber & Ricardo Schiavon. M dyn  2 R e  2 L I e R e 2 I e R e. . . binning:  and  M dyn / L.

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Dissecting the Red Sequence: Star Formation Histories & Mass to Light Ratios

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  1. Dissecting the Red Sequence: Star Formation Histories & Mass to Light Ratios Genevieve J. Graves University of California, Santa Cruz with Sandra Faber & Ricardo Schiavon

  2. Mdyn2Re 2 L Ie Re2 IeRe   binning:  and Mdyn/L at fixed , Re : variations in Ie variations in Mdyn/L bin by  and Mdyn/L

  3. highMdyn /L high Metallicity Hyperplane (MHP) Trager et al. (2000) lowMdyn /L low the metallicity hyperplane

  4.  Mdyn /L   Mdyn /L Mdyn /L  (Age, [Fe/H]) (, Mdyn /L) MHP maps onto FP X-section

  5. Mdyn Mtot Mtot M,real M,real M,IMF M,IMF L Mdyn L = x x x dynamical mass estimator DM fraction IMF variations in Mdyn /L within Re stellar population (age, Z)

  6. SAURON Survey: SLACS Survey: Cappellari et al. (2006) - IFU data, dynamical models Bolton et al. (2007) - strong lensing dynamical mass estimator UW: May 27, 2008

  7. SLACS, SAURON Mdyn Mtot Mtot M,real M,real M,IMF M,IMF L Mdyn L = x x x dynamical mass estimator DM fraction IMF variations in Mdyn /L within Re stellar population (age, Z)

  8. constant M /L Bruzual & Charlot (2003) * the metallicity hyperplane

  9. M / L * M/L vs. Mdyn /L Mdyn / L (SSP) log Mdyn / L log M* / L

  10. SLACS, SAURON not enough Mdyn Mtot Mtot M,real M,real M,IMF M,IMF L Mdyn L = x x x dynamical mass estimator DM fraction IMF variations in Mdyn /L within Re stellar population (age, Z)

  11. Dark Matter, IMF: Mdyn / M  2Re  Mdyn FP midplane two tilts of the FP Stellar Population: M/L log Re M/L   residual tilt:Mdyn / M log Re log 

  12. M / L * M/L vs. Mdyn /L Mdyn / L log Mdyn / L log M* / L

  13. ETG star formation histories = 2-D parameter space • (variations with  and with Mdyn/L) • 2-D family of star formation histories = X-section of FP • Stellar population effects cannot account for observed tilt • of the FP, or the observed thickness of the FP • variations in the IMF or central DM fraction required • high Mdyn/M correlated with short duration star formation • The two tilts of the FP: • Stellar population effects (M/L) and variable IMF or DM • fraction (Mdyn/M) tilts rotate the FP around different axes observational conclusions

  14. more at low end M*/L from Chabrier IMF variations in the IMF? need some galaxies with higher M/L M log (dN / d log M) more at high end high end more attractive to match [Mg/Fe] 0.1 1 10 100 log M (M)

  15. Mdyn /L is measured within Re variation in DM fraction? • genuine lack of stellar mass for given halo mass • (low star formation efficiency) • - early truncation of star formation through quenching? • (by AGN or massive halo) • redistribution of stellar and dark matter inside/outside Re • - gas-rich vs. dry mergers?

  16. early quenching: low Ie, high Mdyn/L Cattaneo et al. (2008) low sf efficiency: halo quenching? late quenching: high Ie, low Mdyn/L naturally produces correlation between Mdyn /L , short duration star formation @ fixed  0 2 4 6 8 z

  17. Nesvadba et al. (2008) 600 0 km/s -600 Galaxy w/ Powerful Radio Jets @ z=2.4 [OIII]5007 emission: * aligned w/ radio lobes * large outflow velocities * outflow mass-loading and lifetime can carry out ~ few x 1010M low sf efficiency: AGN feedback? SF truncated in high Mdyn/L objects

  18. gas fraction of major-merger changes Mdyn / M gas fraction redistribution of stars? 1% ~0.2 dex fgasvaries w/ mass  contributes to FP tilt 40% log Mdyn / M could also have fgasvariations @ fixed   FP thickness long-duration SF  gas-rich mergers R / Re Robertson et al. (2006)

  19. future work • test variable IMF vs. variable DM fraction • - look at galaxy cores where DM should be unimportant • - look for central starburst contribution from gas-rich merger • (2-component galaxy light profiles) • chemical evolution models • - what forms of variable IMFs match both Mdyn/M and [Mg/Fe]? • the role of environment: • - both merger and massive halo explanations imply environment • plays a role • - relations for central galaxies vs. satellites

  20. M / L M / L * * (constant SFR) M/L vs. Mdyn /L Mdyn / L (SSP) log Mdyn / L log M* / L

  21. M/L from Age, [Fe/H]

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