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? …