The Impact of Galactic Outflows Across Cosmic Scales

1
The Impact of Galactic Outflows Across Cosmic
Scales

• Romeel Davé
• Ben D. Oppenheimer
• Kristian Finlator

2
Galactic Outflows
Halo mass function, scaled by Wb/Wm.

• 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
• ?

Outflows
AGN
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Galactic Outflows

• Difficult to observe quantify
• Tenuous, hot, multiphase gas
• Asymmetric intermittent
• Rare locally, but common during heydey of galaxy
  formation (z2)
• Can we constrain outflows by comparing structure
  formation models with data?

M82 Optical Ha
M82 Spitzer/MIPS
M82 Chandra
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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
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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 (zr9)
• 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) vw484 km/s, h2
• m/vzw- Momentum-driven winds L/Led1.05-2,
  h300/s.
• nw- No winds
• New Track C, O, Si, Fe individually from Type II
  Ia SNe and stellar (AGB) mass loss.

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Prevents Overcooling? ?

• Early SF suppressed by factor SFR/ACC ? (1h)-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, z6
RD, Finlator, Oppenheimer 06
Oppenheimer RD 06
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Enriches IGM? ?

• WCIV shows curious constancy from z6?2 Early
  (zgt6) enrichment?
• NOconstancy of WCIV reflects evolving ionization
  state, not non-evolving metallicity.
• Wind energy heats IGM!

Oppenheimer RD 06
8
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
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Galaxy Mass-Metallicity Relation
Tremonti etal 04

• Observed Zgas?M0.3 from M106?1010.5M?, then
  flattens. Low scatter, s0.1.
• 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
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What Drives the MZR?

• Momentum-driven scalings uniquely match z2 data.
• MZR is an equilibrium state of gas accretion
  (ACC) vs. star formation (SFR).
• Zeq y SFR/ACC y/(1heff).
• cw M1010M? have halos with vescvw484 km/s,
  hence above this heff?0.
• cw generically predicts a feature in MZR at
  vescvw!
• vzw heffh, so for low M, Z?1/h?s?M1/3,
  flattens _at_ h1 As observed!

No winds
Finlator RD 07
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MZR Scatter

• Lee etal 06 noted that DekelSilk scenario
  over-produces scatter at low M.
• In our model, scatter comes from departures from
  Zeq from stochastic accretion.
• Timescale to return to Zeq tdACC/Mgas (dilution
  time).
• Small td ? low scatter.
• Only MD winds have tdlttvir at all epochs masses.

Finlator RD 07
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ICM Enrichment? ?
RD etal in prep

• New 64 Mpc/h run to z0 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 Tgt0.5 keV, as
  observed!
• ICM enrichment occurs naturally using same
  outflows needed to enrich IGM, etc.

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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/?

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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 h1/s, with
  h1 at M1010.5M?.
• 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??

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The M-SFR Relation
Daddi etal 07 z1.4-2.5

• Gas accretion ? star formation
• M-SFR constrains SFH form
• Observations of SFGs (z0-2)
• M?SFR0.7-0.9 at all z.
• Small scatter (lt0.3 dex) around main sequence
  of SFGs.
• Evolution is M-independent.

Elbaz etal 07 z0.8-1.2
Noeske etal 07 z0.2-1.1
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M-SFR vs. Models

• Green Millenium SAM
• Red, magenta SPH
• Blue Data (s0.3)
• Slope ltunity? ?
• Scatter small? ?
• Evolves independent of M? ?
• Evolves at observed rate?

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Star Formation Activity Parameter

• (i.e. fraction of Hubble time required to form
  M at current SFR).
• Models asf1 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

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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 z2, and x2 at z1 This would yield
  unevolving asf.
• Larson (98,05) IMF today has Mchar0.5 M?.
  High-z ISM hotter ? Mchar higher.
• Evolving Kroupa IMF (0.1-100 M?)
• dN/dlogM?M-0.3 for MltMchar.
• dN/dlogM?M-1.3 for MgtMchar.
• Mchar0.5(1z)2 M? ? from PEGASE modeling