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Chemical Evolution in the Universe (and galaxies)

Romeel Davé Kristian Finlator Ben D. Oppenheimer University of Arizona. Chemical Evolution in the Universe (and galaxies). Metals in the Universe. Most metals are not in galaxies (Pettini 99), but rather the IGM.

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Chemical Evolution in the Universe (and galaxies)

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  1. Romeel Davé Kristian Finlator Ben D. Oppenheimer University of Arizona Chemical Evolution in the Universe (and galaxies)

  2. Metals in the Universe • Most metals are not in galaxies (Pettini 99), but rather the IGM. • IGM tells us: Metals must be transported over large (~Mpc) scales, starting early on. • Outflows establish the balance of metals in various cosmic baryon phases. • … or in reverse, observations of metals in various phases can constrain outflows. • Idea: Use cosmological simulations + observations to constrain outflow properties and understand chemical enrichment.

  3. Outflows typical at high-z Common at z~1+: ΣSFR>>0.1 M⊙/kpc2 ΔvISM~ hundreds km/s Local SBs, z~1 SFG: vwvcircMomentum-driven winds? If so, outflow rate η1/vcirc where h = Moutflow/M*. How do outflows impact IGM & galaxies? Use metals as tracers. M82: Spitzer 8μ Martin 2005 100

  4. Outflows in Gadget-2 Kick particles with vw, in vxa direction. Monte Carlo: Proboutflow=ηProbSF vw and η related to Mgal(s) and SFR. For mom-driven winds (OD08): Recycling time ~1 Gyr, distance~100 physical kpc http://luca.as.arizona.edu/~oppen/IGM/

  5. Chemical Enrichment • Track 4 metals: C, O, Si, Fe. • 3 sources: Type II + Ia SN, AGB stars. • AGB stars return mass+Z into ISM. • Star-forming gas is continually self-enriched. When ejected, it carries metals into IGM. No diffusion. • Primary constraint: IGM enrichment. • Winds are only way to get metals out that far, that early!

  6. IGM too hot Too few metals in IGM Momentum-driven wind scalings! Too few metals produced wind speed Diffuse IGM unenriched mass loading IGM enrichment • Goldilocks & 3 winds: • Momentum-driven scalings • Weak (E<ESN) • Constant (vw~500km/s,η=2) ~ log δ Oppenheimer & RD 2006

  7. Luminosity functions Data: Bouwens etel 06 Models: =0.3, 8=0.9 RD, Finlator, Oppenheimer 06 • z~6 UVLF: large SF suppression. • Rapid consumption  must eject gas. • Macc = M*+Moutflow  SFR (1+h)-1 • z~2-4 LF: • Const ha~2+ • h ~ vc-1a~1.7 • z=0: Faint end slope of F(M*) not too bad! (bright end?… ugly)   

  8. Mass-Metallicity Relation Tremonti etal 04 • Observed: ZgasM*0.3 from M*~1061010.5M, then flattens. Low scatter, s≈0.1. • Conventional thinking: • Zgas reflects current stage of gas reservoir processing. • Winds carry metals more easily out of small galaxies. • WRONG !!! (at least according to our simulations) Lee etal 06

  9. z=2 Finlator&RD 08 MZR: Clues from Sims vs. Data • vwind=const, h=const fails. • vwind~vesc , h~1/vesc works! • Why? • Because outflows are greedy & destructive: • They don’t share their energy • They blow holes Z~M1/3 Analytic 3D simulation

  10. z=2 Finlator&RD 08 The Equilibrium Model   • Z ~ y M*/Macc ~ y (1+h)-1 • If vw>vesc, constant h constant Z. For vw<vesc, h0, Zy. Produces a feature in MZR-- not seen. • For mom-driven winds: h~M*-1/3~vc-1Z(M*)~M*1/3 • Zgas set by an equilibrium between recent inflow and outflows. Z~M1/3

  11. MZR Evolution • M*-Z relation is predicted to have slow evolution from z=40 (0.05 dex/z). • Only note slope, evolution, & scatter; amplitude ±0.3+. • Galaxies enrich early! • Turnover at hi-M due to h<1 at large s, not potential well (recall Z~y/(1+h) , h1/s) RD, Finlator, Oppenheimer 06

  12. MZR Scatter • Lee etal 06 noted that standard scenario over-produces scatter at low M*. • In our model, scatter comes from departures from Zeq from stochastic accretion/merging. • Timescale to return to Zeq: td=Mgas/Macc (dilution time). • Small td low scatter. • MD winds have td<tdyn at all epochs & masses.  Finlator & RD 07

  13. Baryon fractions • Winds keep galaxies gas-rich. • …but only if mass loading is large in small galaxies! • Galaxies lose sub-stantial mass early. • MW sized halo at z=0 has half its “share” of baryons. z=0 z=2

  14. ICM Enrichment & Pre-heating • LX-weighted [Fe/H]~1/3 Z, as observed. • No winds looks ok, but stellar baryon fraction >> observed; spurious! •  Need outflows to spread baryons in ICM. • Intragroup gas shows excess entropy over no winds; “pre-heating”. • ICM is pre-heated to correct levels naturally with outflows. RD etal in prep

  15. Summary Star formation and enrichment in galaxies strongly regulated by outflows. Generally, need more mass loss from smaller galaxies. Momentum-driven scalings work well: Mass-metallicity relation slope & scatter. IGM enrichment (CIV @z~2-4, OVI at z~0) Keeps small galaxies gas-rich, with less stars. Bonus: Consistent with observed winds. Mass-metallicity relation set by equilibrium between recent inflows and outflows, governed by outflow rate not potential wells.

  16. Discussion Topics • Best direct way to constrain outflows? • ISM absorption: Velocity info but not dM/dt. • X-ray emission: Energy info, but little else. • Best indirect way to constrain outflows? • IGM absorption (feedback tomography) • Mass-metallicity relation • Stellar mass evolution (i.e. SF efficiency) • Does [a/Fe] tell us anything about outflows? • How can MW studies of accretion/SF help? • Is a closed box model OK for passive gals? • Where do AGB products (e.g. C) end up?

  17. Reionization Epoch • Galaxy formation different? • Radiative feedback • Non-equilibrium ionization • Mini-halo contribution? • Top-heavy/Pop III IMF? • Mini-quasars? • Basic questions: • Topology: Outside-in, inside-out, or ??? • Enough photons from “normal” IMF?

  18. Typical SF Histories: Rapid, Early Assembly Gadget simulations vs. z>5.5 galaxies w/IRAC data. In most cases, simul-ated galaxies provide good fit (2<1). Best-fit galaxies… are fairly massive, have older stars, show 4000Å break. Typical SFH is constantly rising. log M*=9.3 log M*=8.7 log M*=10.1 log M*=10.1 log M*=9.2 log M*=9.4 Finlator, RD, Oppenheimer 06

  19. Let's do it right: Rad Hydro Moment-based scheme (like OTVET, without the “OT”, i.e. optically thin assumption). Use long characteristics to compute Eddington tension and close moment hierarchy. For now, post-process hydro outputs. SFHSpectrum (BC03) Working on combining w/Gadget. 1 2 Finlator, Ozel, RD 08 3

  20. If we suppress SF, does that hamper ability to reionize? Even w/10% escape fraction, plenty of photons! Key: Clumping factor much lower than often assumed (30). Clumping factor evolves strongly! Enough photons to reionize? Fan+06 Gnedin & Ostriker (1997) Pawlik & Schaye (2008); Bolton & Haehnelt (2008) Finlator et al 08, in prep

  21. Topology Evolution? • Outside-in? Miralda-Escude et al 00 • Inside-out? Simulations; eg Iliev etal 06 • Our result: Insideoutsidemiddle! (see also Choudhury etal) http://norno.as.arizona.edu/~kfinlator/rt/index.html

  22. Early Galaxy Formation Galaxies & IGM connected via outflows. Outflow rate >~ star formation rate Accretion ≃ SFR + Outflow rate Early star formation: It's NEVER too big for CDM (almost). Mass-metallicity relation from outflows: Not what you think. Are there enough photons to reionize the Universe by z=9?

  23. Constant winds Mom-driven winds No winds no winds, 8e-5 constant winds, 0.037 MD winds, 0.51 DLA Kinematics: Outflows? • Wide separation (v>vrot) DLAs hard to produce; protogalactic clump infall fails (Pontzen etal). • Momentum-drive winds puff out gas, produces wide-separation systems. S. Hong, Katz, RD etal, in prep Prochaska & Wolfe 01 KS test prob

  24. Constant CIV ≠ Early IGM Enrichment • CIV~constant (z=2-5.5). • Simple model: Pop III stars inject metals at z>6. • WRONG. • Successful wind models show CIV~constant, but CIV increasing by x10. • Early injection yields CIV increasingCIV! • Hence constant CIVsupports in situ enrichment. Oppenheimer & RD 06

  25. Missing metals Pettini 99: Metals in z~3 galaxies << Metals produced by stars. Strong outflows? Simulations: 40% of metals in diffuse IGM @ z=3; only 10% in stars, 10% in cold gas. Shocked IGM (WHIM) has ~20% at all z. But is it only metals ejected, or mass? RD & Oppenheimer 07

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