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Global Accretion and Feedback Processes in Galaxy Formation

Global Accretion and Feedback Processes in Galaxy Formation. Romeel Davé Ben D. Oppenheimer Kristian Finlator. Galactic Outflows. Cold mode accretion is dense & filamentary  Need bouncer feedback to prevent overcooling: Outflows

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Global Accretion and Feedback Processes in Galaxy Formation

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  1. Global Accretion and Feedback Processes in Galaxy Formation Romeel Davé Ben D. Oppenheimer Kristian Finlator

  2. Galactic Outflows • Cold mode accretion is dense & filamentary  Need bouncer feedback to prevent overcooling: Outflows • Constrain outflow properties by comparing hydro simulations to outflow-related observations, e.g.: • IGM enrichment [Oppenheimer & RD 06] • Early galaxies & overcooling [RD, Finlator, Oppenheimer 07] • Mass-metallicity relation [Finlator & RD 07] • DLA kinematics [S. Kim, Katz etal in prep] • ICM metals & energy [RD etal in prep] • A single wind scaling relation matches all these!

  3. Martin 2005 Quantifying Outflows Erb etal 06 z~2 SFG’s • Outflows rare locally, but probably the norm at z>~2. • Two basic parameters: • Outflow velocity: vw • Mass loading factor: h • Martin 05, Rupke etal 05: Starbursts show vwvcirc. • Such a scaling arises in momentum-driven winds: vws, h1/s • Implement into Gadget-2, Monte Carlo ejection of particles, s computed from Mgal using on-the-fly finder. M82 MIPS Engelbracht etal log h

  4. Erb et al 2006 High-z Luminosity Functions • Early SF suppressed by factor SFR/ACC  (1+h)-1. • Momentum-driven winds work well because h1/s is large for early galaxies. • Poor constraint on winds; depends on dust,s8,IMF,… Data: Bouwens etal 06, z~6 RD, Finlator, Oppenheimer 06 Oppenheimer & RD 06

  5. Gas & Baryonic Content • h1/s keeps smaller galaxies more gas-rich; decent match to z=2 data (Erb etal). • Other wind models don’t match. • Baryonsejectedfrom halos: By z=0, ~40% of baryons in MW halo have gone into the IGM! Green: z=3 Black: z=0

  6. Tremonti etal 04 Lee etal 06 Galaxy Mass-Metallicity Relation • 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 have characteristic speed, so they carry metals more easily out of small galaxies (Dekel & Silk 86). • Wrong! (at least according to our models)

  7. No winds Momentum- driven scalings Constant vw,h What Drives the MZR? • Momentum-driven scalings uniquely match z~2 data. • MZR set by an equilibrium between accretion & SFR. • Zeq = y SFR/ACC ≈ y/(1+heff). • cw: M*~1010M have halos with vesc~vw=484 km/s, hence above this heff0. • cw generically predicts a feature in MZR at vesc≈vw! • vzw:heff~h, so for low M*, Z1/hsM*1/3, flattens @ h~1: As observed! Finlator & RD 07

  8. Intergalactic Fountains • New models: sMgal1/3, metals from Type II, Ia, stellar evol. • WCIV evol matches data; Carbon from AGB stars imporant at z<0.5. • Winds always exceed escape energy, but much less so at low-z. Oppenheimer & RD, in prep

  9. Recycling • Recycling time ~ 1 Gyr, • Strong decrease with Mgal, because of denser environment. Oppenheimer & RD, in prep

  10. Trouble in Paradise: M*-SFR Relation • M*-SFR reflects form of star formation history. • Models match at z~0, progressively low SFR and/or high M* to z~2. (x5 @ z~2) • Model SFH’s (i.e. cold accretion) generically wrong? • Systematics in SFR/M*? Possible, but requires something dramatically different from z~0. • Top-heavy IMF? Don’t go there… Models Data

  11. Summary • It is now possible to constrain basic outflow parameters across cosmic time by comparing sophisticated hydro simulations to data. • Momentum-driven wind scalings can match a wide range of data; some interesting insights. • Generically, need lots of gas ejected from early/small galaxies. • Feedback cycle returns ejected materials on ~Gyr timescales; lower mass galaxies throw material farther out. • Many questions: Does AGN feedback screw this up? Are winds really mom-driven? How tightly do data constrain scalings? Other data? …

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