Simulations of Reionization- Epoch Galaxies Romeel Davé (Arizona) Kristian Finlator, Ben D. Oppenheimer

Galaxies at z>6: Why? Responsible for reionizing the universe. Responsible for reionizing the universe. Test early galaxy formation models. Test early galaxy formation models. Now observed! Now observed! What are their physical properties? What are their physical properties? What constraints do they place on models? What constraints do they place on models? Movie by N. Gnedin z~7 arc in Abell 2218 Kneib et al 2004

Cosmological Hydro Simulations Gadget-2 (PM-Tree-eSPH), with new momentum-driven wind models + metal-line cooling (no H 2 ). Gadget-2 (PM-Tree-eSPH), with new momentum-driven wind models + metal-line cooling (no H 2 ). Reproduces observed IGM metals at z~2-5 (Oppenheimer & RD 06) Reproduces observed IGM metals at z~2-5 (Oppenheimer & RD 06) 2x256 3 runs,  CDM, [8,16,32,64]h -1 Mpc, various outflows. 2x256 3 runs,  CDM, [8,16,32,64]h -1 Mpc, various outflows. No radiative transfer, uniform HM01 (QG01) z~9. No radiative transfer, uniform HM01 (QG01) z~9. Feedback cycle tracked self-consistently; geometry critical. Feedback cycle tracked self-consistently; geometry critical. Movie by B. Oppenheimer 3 Mpc/h comoving

Rest-UV Luminosity Functions nw: no winds; cw: “constant” winds, v w =484 km/s (Springel & Hernquist 2003); mzw/vzw: momentum-driven winds, v w  (from local starbursts; Martin 2005). nw: no winds; cw: “constant” winds, v w =484 km/s (Springel & Hernquist 2003); mzw/vzw: momentum-driven winds, v w  (from local starbursts; Martin 2005). Matches rest-UV LF at z~4-6; steep faint-end! Matches rest-UV LF at z~4-6; steep faint-end! z~6: Large suppression of SF needed at early times, across all masses. z~6: Large suppression of SF needed at early times, across all masses. GOODS B-dropouts Bouwens et al 06 RD, Finlator, Oppenheimer 06

Stellar Mass buildup Despite large suppression, stellar mass builds up quickly. Despite large suppression, stellar mass builds up quickly. At z=7, space density of M * >10 10 M  objects ~ SDSS LRG’s today. At z=7, space density of M * >10 10 M  objects ~ SDSS LRG’s today. Halos masses ~100M * ~ M   Atomic line cooling dominates. Halos masses ~100M * ~ M   Atomic line cooling dominates. Tight M*-SFR relation driven by cold-mode accretion (Keres etal 05). Tight M*-SFR relation driven by cold-mode accretion (Keres etal 05). RD, Finlator, Oppenheimer 06 ~JWST depth

Galaxies Self-Reionize Early Lots of SF  lots of ionizing photons Lots of SF  lots of ionizing photons Stromgren sphere overlap as a function of M * : Percolation at z»9 for M * <10 9 M . Stromgren sphere overlap as a function of M * : Percolation at z»9 for M * <10 9 M . Combined with large v circ  Rad Xfer not critical for studying 6<z<9 galaxies. Combined with large v circ  Rad Xfer not critical for studying 6<z<9 galaxies. RD, Finlator, Oppenheimer 06 Zahn et al 2006

Galaxies Self-Enrich Quickly …despite strong outflows that enrich IGM. …despite strong outflows that enrich IGM. Typical ~ Z z~6, very little evolution with z. Typical ~ Z z~6, very little evolution with z. M * -Z rel’n evolves slowly to z~2, agrees with Erb etal 06. M * -Z rel’n evolves slowly to z~2, agrees with Erb etal 06. Very little “metal free” SF (Z<10 -3 Z  ); bulk of IMF normal. Very little “metal free” SF (Z<10 -3 Z  ); bulk of IMF normal. RD, Finlator, Oppenheimer 06 Points: Erb etal 06 z~2 Line: SDSS z~0

Case Study: Abell 2218 KESR z~6.7 galaxy well-fit by simulated, independent of outflows/cosmology. z~6.7 galaxy well-fit by simulated, independent of outflows/cosmology. This galaxy is typical: M * and SFR fall exactly on simulation’s tight M * -SFR correlation. This galaxy is typical: M * and SFR fall exactly on simulation’s tight M * -SFR correlation. Star formation history best characterized by steady rise; NOT constant, decaying, or single-burst; yet all models fit with  2 <1. Star formation history best characterized by steady rise; NOT constant, decaying, or single-burst; yet all models fit with  2 <1. Finlator, RD, Oppenheimer 06

SPOC: Physical Constraints from Simulated Galaxies SPOC: Bayesian engine to constrain physical parameters from photometric data by comparison with simulated sample. SPOC: Bayesian engine to constrain physical parameters from photometric data by comparison with simulated sample. Provides tighter constraints than “toy model” SFHs because simulated SFHs are ~self-similar. Provides tighter constraints than “toy model” SFHs because simulated SFHs are ~self-similar. Also tests model: If “prior” is wrong, no good fit obtained! Also tests model: If “prior” is wrong, no good fit obtained! Finlator, RD, Oppenheimer 06

Constraining z~6 Galaxies 6 observed objects have M * ~ M , SFR~2-50 M  /yr. 6 observed objects have M * ~ M , SFR~2-50 M  /yr. All well-fit by simulated galaxies except GLARE#3001; this one poorly fit by ALL models, seems “bursty”. All well-fit by simulated galaxies except GLARE#3001; this one poorly fit by ALL models, seems “bursty”. SPOC identifies outlier objects that critically test models. SPOC identifies outlier objects that critically test models. Finlator, RD, Oppenheimer 06  2 ~3  2 ~8

Summary Galaxies at 6 ~0.1Z , live in reionized regions by z~9. Galaxies at 6 ~0.1Z , live in reionized regions by z~9. Simulations can match observed luminosity function if feedback heavily suppresses star formation by z~6. Simulations can match observed luminosity function if feedback heavily suppresses star formation by z~6. Mass-metallicity relation evolves very slowly, and even at z~9 there is little Population III star formation. Mass-metallicity relation evolves very slowly, and even at z~9 there is little Population III star formation. Individual observed galaxies are straightforwardly accommodated in simulations, and in turn models be used to constrain physical parameters using SPOC. Individual observed galaxies are straightforwardly accommodated in simulations, and in turn models be used to constrain physical parameters using SPOC.