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The Impact of Galactic Outflows Across Cosmic Scales

The Impact of Galactic Outflows Across Cosmic Scales. Romeel Davé Ben D. Oppenheimer Kristian Finlator. Halo mass function, scaled by W b / W m. Galactic Outflows. Outflows. Feedback process from young stars drive mass, metals & energy from star-forming regions.

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The Impact of Galactic Outflows Across Cosmic Scales

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  1. The Impact of Galactic Outflows Across Cosmic Scales Romeel Davé Ben D. Oppenheimer Kristian Finlator

  2. Halo mass function, scaled by Wb/Wm. Galactic Outflows Outflows • Feedback process from young stars drive mass, metals & energy from star-forming regions. • Regulates SF, along with BHs, photoheating, … • Galactic outflows thought to be responsible for: • preventing overcooling • flattening faint-end of LF • enriching IGM & ICM(?) • mass-metallicity relation • …? AGN

  3. Erb etal 06 z~2 SFG’s Galactic Outflows • Difficult to observe & quantify • Tenuous, hot, multiphase gas • Asymmetric & intermittent • Rare locally, but common during heydey of galaxy formation (z~2) • Can we constrain outflows by comparing structure formation models with data? M82: Optical + Ha M82: Spitzer/MIPS M82: Chandra

  4. Martin 2005 Quantifying Outflows • Two basic parameters: • Outflow velocity: vw • Mass loading factor: h • Martin 05, Rupke etal 05 (using NaI absorbers): Starbursts show vwvcirc. • Such a scaling arises in momentum-driven winds: vws, h1/s • Murray, Quataert, Thompson 05: Dust is radiation-driven, couples to gas out to ~Rvir, drives outflow. log h MQT05

  5. Simulating Cosmic-scale Outflows • Gadget-2 (Springel 05): PM-Tree-ECSPH. • SF: Subgrid multi-phase ISM model incorporating thermal feedback. Continual enrichment. • Cooling: Primordial + metal-line cooling (SD93). • Ionizing background: Haardt & Madau 2001 (zr≈9) • 2x2563 particles, box sizes from 864 Mpc/h. • Monte Carlo ejection of star-forming particles, kicked with velocity vw in vxa, with probabilityh. • Wind models: (many more tried; see OD06) • cw- Constant winds (SH03): vw=484 km/s, h=2 • m/vzw- Momentum-driven winds: L/Led=1.05-2, h=300/s. • nw- No winds • New: Track C, O, Si, Fe individually from Type II & Ia SNe and stellar (AGB) mass loss.

  6. Erb et al 2006 Prevents Overcooling?  • 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; dependent on dust,s8,IMF Data: Bouwens etal 06, z~6 RD, Finlator, Oppenheimer 06 Oppenheimer & RD 06

  7. Successful winds Weak winds Enriches IGM?  • WCIV shows curious constancy from z~62: Early (z>6) enrichment? • NO…constancy of WCIV reflects evolving ionization state, not non-evolving metallicity. • Wind energy heats IGM! Oppenheimer & RD 06

  8. d2N dNHIdz Enriches IGM?  • Spatial distribution of CIV (relative to HI) best reproduced in momentum-driven wind models. • Must not overheat IGM (i.e. too many wide lines). •  Broad constraints on vw, h.: Must be • high enough h and vw to get metals out • …but not so high as to over-pollute and overheat IGM.  log d fraction Oppenheimer & RD 06

  9. Galaxy 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 have characteristic speed, so they carry metals more easily out of small galaxies (Dekel & Silk 86). • WRONG !!! (at least according to our simulations) Lee etal 06

  10. Momentum- driven scalings Constant vw,h What Drives the MZR? • Momentum-driven scalings uniquely match z~2 data. • MZR is an equilibrium state of gas accretion (ACC) vs. star formation (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! No winds Finlator & RD 07

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

  12. ICM Enrichment?  RD etal in prep • New 64 Mpc/h run to z=0 tracking individual metals • Identify clusters as virialized halos, compute LX, TX, s, Fe/H, O/H, etc. • LX-weighted [Fe/H]~1/3 Z for T>0.5 keV, as observed! • ICM enrichment occurs naturally using same outflows needed to enrich IGM, etc.

  13. ICM “Pre-heating”?  RD etal in prep • X-ray scaling relations (e.g. LX-TX) deviate from self-similarity as observed. • ICM pre-heating also occurs naturally with outflows. • Note: Does NOT solve cooling flow problem – need AGN/conduction/?

  14. Summary • It is now possible to constrain basic outflow parameters across cosmic time by comparing sophisticated hydro simulations to data. • IGM CIV absorbers and early SF require high mass outflow rates at early times. • Mass-metallicity relation suggests h~1/s, with h~1 at M*≈1010.5M. • ICM enrichment and “pre-heating” occurs naturally with such outflows. • Momentum-driven wind scalings are amazingly successful at matching a wide range of data. • We must be on to something here… but what does it actually mean??

  15. The M*-SFR Relation Daddi etal 07 z~1.4-2.5 • Gas accretionstar formation • M*-SFR constrains SFH form: • Observations of SFGs (z~0-2): • M*SFR0.7-0.9at all z. • Small scatter (<0.3 dex) around “main sequence” of SFGs. • Evolution is M*-independent. Elbaz etal 07 z~0.8-1.2 Noeske etal 07 z~0.2-1.1

  16. M*-SFR vs. Models • Green: Millenium SAM • Red, magenta: SPH • Blue: Data (s=0.3) • Slope <~unity?  • Scatter small?  • Evolves independent of M*?  • Evolves at observed rate? ×

  17. Models Data 1011M 1010.5 log SFR (Mo/yr) 1010 109.5 Star Formation Activity Parameter (i.e. fraction of Hubble time required to form M* at current SFR). • Models: asf~1 at all z. • Cold accretion  similar forms of SFH at all M*. • Observed: asf(z) evolves strongly. Oops! • Possibilities: • Simulated SFH wrong? • Measurements wrong? • Or…

  18. IMF wrong?[insert Stacy McGaugh MOND dance] • Need less M* formed per unit high-mass SF • Conservatively, SFR/M* should be reduced by ~x3 at z=2, and ~x2 at z=1: This would yield unevolving asf. • Larson (98,05): IMF today has Mchar≈0.5 M. High-z ISM hotter  Mchar higher. • “Evolving Kroupa” IMF (0.1-100 M): dN/dlogMM-0.3 for M<Mchar. dN/dlogMM-1.3 for M>Mchar. Mchar=0.5(1+z)2 M from PEGASE modeling

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