global accretion and feedback processes in galaxy formation
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Global Accretion and Feedback Processes in
Galaxy Formation Romeel Davé
Ben D. Oppenheimer
Kristian Finlator
Galactic Galactic OutflowsOutflows• 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!
Quantifying Quantifying OutflowsOutflows
• Outflows rare locally, but probably the norm at z>~2.
• Two basic parameters:
– Outflow velocity: vw
– Mass loading factor: • Martin 05, Rupke etal 05:
Starbursts show vwvcirc. • Such a scaling arises in
momentum-driven winds: vw, 1/
• Implement into Gadget-2, Monte Carlo ejection of particles, computed from Mgal using on-the-fly finder.
Martin 2005log
Erb etal 06z~2 SFG’s
M82 MIPSEngelbracht etal
High-z Luminosity High-z Luminosity FunctionsFunctions
• Early SF suppressed by factor SFR/ACC (1+)-1.
• Momentum-driven winds work well because 1/ is large for early galaxies.
• Poor constraint on winds; depends on dust,8,IMF,…
RD, Finlator, Oppenheimer 06
Oppenheimer & RD 06
Erb et al 2006
Data: Bouwensetal 06, z~6
Gas & Baryonic ContentGas & Baryonic Content• 1/ keeps smaller galaxies
more gas-rich; decent match to z=2 data (Erb etal).
• Other wind models don’t match.• Baryons ejected from halos: By
z=0, ~40% of baryons in MW halo have gone into the IGM!
Green: z=3Black: z=0
Galaxy Mass-Galaxy Mass-Metallicity Metallicity RelationRelation
• Observed: ZgasM*0.3 from
M*~1061010.5M, then flattens. Low scatter, ≈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)
Tremonti etal 04
Lee etal 06
What Drives the What Drives the MZR?MZR?
• Momentum-driven scalings uniquely match z~2 data.
• MZR set by an equilibrium between accretion & SFR.
• Zeq = y SFR/ACC ≈ y/(1+eff).• cw: M*~1010M have halos
with vesc~vw=484 km/s, hence above this eff0.
• cw generically predicts a feature in MZR at vesc≈vw!
• vzw: eff~, so for low M*, Z1/M*
1/3, flattens @ ~1: As observed! Finlator & RD 07
Momentum-drivenscalings
Constant vw,
No winds
Intergalactic Intergalactic FountainsFountains
• New models: Mgal1/3,
metals from Type II, Ia, stellar evol.
• CIV 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
RecyclingRecycling• Recycling time ~ 1 Gyr, • Strong decrease with Mgal,
because of denser environment.
Oppenheimer & RD, in prep
Trouble in Trouble in Paradise: Paradise:
M*-SFR RelationM*-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
SummarySummary• 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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