star formation at high redshift: observational progress and theoretical perspectives
DESCRIPTION
Romeel Davé. movie by B. Oppenheimer. Star Formation at High Redshift: Observational Progress and Theoretical Perspectives. Cosmic SF History. Madau et al 1996. x10 from z=1-0. ~flat z=4-1. rising to z~4. - Systematics >~x2 - Sample overlap?. Hopkins & Beacom 2006. - PowerPoint PPT PresentationTRANSCRIPT
Star Formation at High Redshift:Star Formation at High Redshift:Observational Progress and Observational Progress and
Theoretical PerspectivesTheoretical Perspectives
Romeel DavéRomeel Davé
movie by B. Oppenheimer
Cosmic SF HistoryCosmic SF HistoryMadau et al 1996
Hopkins & Beacom 2006
x10 from z=1-0
~flatz=4-1
risingto z~4
- Systematics >~x2- Sample overlap?
Breaking down cosmic SFBreaking down cosmic SF Bursty or quiescent?Bursty or quiescent? How important are mergers?How important are mergers? How much is obscured?How much is obscured? Stellar mass growth vs. SFR?Stellar mass growth vs. SFR? Is hi-z SF systematically different?Is hi-z SF systematically different?
Main Sequence of Galaxy Main Sequence of Galaxy
FormationFormation
SFR ~ MSFR ~ M**0.7-0.90.7-0.9, scatter 0.3 dex., scatter 0.3 dex.
Evolves down independently of MEvolves down independently of M** SFR quiescent, not burst, dominatedSFR quiescent, not burst, dominated
Noeske etal 07z~0.2-1.1
Daddi etal 07z~1.4-2.5
Elbaz etal 07z~0.8-1.2
Labbe etal 10z~7
SFR from mergers?SFR from mergers?
Close pairs: <10% global SF in >3:1 mergersClose pairs: <10% global SF in >3:1 mergers Morphological: <30% global SF in interactingMorphological: <30% global SF in interacting BUT– Asymmetry: ~50% z~1 SF in “mergers”BUT– Asymmetry: ~50% z~1 SF in “mergers” Non-interacting galaxies dominate SFRDNon-interacting galaxies dominate SFRD
Robaina et al 2009
Jogee et al 2009
Shi+09
Bouwens+09
Obscured star formationObscured star formation
Most SF obscured; peaks at z~2.Most SF obscured; peaks at z~2. LIRGs/ULIRGs dominate to z~1,2…but don’t LIRGs/ULIRGs dominate to z~1,2…but don’t
interpret as local ULIRG analogs!interpret as local ULIRG analogs!
Dust productionSF to disks
Seymour+09
SFR vs. dMSFR vs. dM**/dt/dt
dM*/dt << SFR (+IMF) at z~2-3dM*/dt << SFR (+IMF) at z~2-3 Completeness? (Reddy+09)Completeness? (Reddy+09) Is SFR at z~2-3 fundamentally different?Is SFR at z~2-3 fundamentally different?
RD 08
Wilkins+ 09
How Do We Understand All How Do We Understand All
this?this? ComputersComputers!!
A Not-totally-wrong Story A Not-totally-wrong Story for Star-forming Galaxiesfor Star-forming Galaxies
Cold flowsCold flows Smooth accretionSmooth accretion Regulation by galactic outflowsRegulation by galactic outflows The Galaxy-IGM connectionThe Galaxy-IGM connection Truncation by mergers/AGNTruncation by mergers/AGN
Cold mode Cold mode accretionaccretion
Cold flows dominate gas infall for ALL star-forming galaxies.
Hot halos for >1012 M
InfallfromIGM
disk
Rvir
Rcool
Dekel+ 09 z=2, AMR
At z>~1-2, flows penetrate hot halo.
At low-z, flows break up into clouds (HVCs?)
z=2, 1012M halo z=1, 1013M halo
Keres+ 09
Cold Mode -- in every hydro sim ever doneCold Mode -- in every hydro sim ever done
SFR tracks accretionSFR tracks accretion
SFGs at all masses, epochs SFGs at all masses, epochs process accreted gas into process accreted gas into stars on t<<tstars on t<<tHH
Keres+09
Accretion is SmoothAccretion is Smooth
Accretion is ~smooth Accretion is ~smooth (& filamentary).(& filamentary).
Mergers subdominant.Mergers subdominant.
Keres etal 09
Generic predictionsGeneric predictions Tight SFR-MTight SFR-M** relation, relation,
evolves indep of Mevolves indep of M** Mergers/bursts sub-Mergers/bursts sub-
dominant in SFRD.dominant in SFRD. Disturbed morphology due Disturbed morphology due
to rapid accretionto rapid accretion Early galaxies grow Early galaxies grow
rapidly.rapidly.
… … too too rapidly!rapidly!
Need feedback.Need feedback.RD 08
Bournaud+ 07: Unstable disk sim
Data: Bouwens+06 z~6RD et al 06
Feedback Regulates SFFeedback Regulates SFHalo mass function, scaled by b/m.
Baldry+ 08
Cosmic Feedback CycleCosmic Feedback Cycle
Outflows: Observations & Outflows: Observations & ImplicationsImplications
Common at z~1+: ΣSFR>>0.1 M⊙/kpc2
ΔvISM~ hundreds km/s Local SBs, z~1 SFG: vwvcirc
Momentum-driven winds? If so, mass loading factor
η1/vcirc Note: Similar scalings may
arise from other physical mechanisms.
M82: Spitzer 8μ
Martin 2005
100
Correct (early) evolution of cosmic SFR IGM enriched to match CIV, OVI absorbers Mass-metallicity with right slope & scaller High gas fractions in low-M galaxies DLA kinematics w/enough wide systems Non-grav entropy in intracluster gas
… all from including one simple scaling of outflows with galaxy mass.
Such Outflows Yield…Such Outflows Yield…
Mass in outflows >> Mass in stars
Winds recycle a lot; recycled wind accretion dominates at z<~1.
Many baryons blown out of even large halos
Outflows keep galaxies gas rich (not poor).
MZR set by balance of inflows and outflows, not gas processing rate
… … Some Surprising Some Surprising ImplicationsImplications
Mwind ~ 3 M*
Median Nrecyc~3
BDO & RD 08
Z~M1/3
The “Equilibrium” The “Equilibrium” MZR ModelMZR Model
z=2
Finlator&RD 08
Z ~ y M*/Macc ~ y (1+)-1
If vw>vesc, constant constant Z. For vw<vesc, 0, Zy. Produces a feature in MZR-- not seen.
For mom-driven winds: ~M*
-1/3~vc-1 Z(M*)~M*
1/3
Zgas set by an equilibrium between recent inflow and outflows.
680 km/s
340 km/s
vw~vcirc
Recycling sets the GSMFHalo mass function, scaled by b/m.
Baldry+ 08
trec short;Lots of recycled wind mode
trec longer;Lessrecycled wind mode
trec > thubble;Norecycled wind mode
trec irrelevant;Need to quench star formation!
Galaxies as “Gas Galaxies as “Gas Processing Engines”Processing Engines”
Obtain gas via cold, smooth accretionObtain gas via cold, smooth accretion Creates tight evolving MCreates tight evolving M**-SFR relation.-SFR relation.
Process into stars (some) or eject into Process into stars (some) or eject into outflows (most) on a short timescale.outflows (most) on a short timescale. SFR, gas content, metallicity set by SFR, gas content, metallicity set by
balance of inflow vs outflow.balance of inflow vs outflow. Ejected material recycles, moreso in Ejected material recycles, moreso in
larger galaxies.larger galaxies. Sets shape and evolution of galaxy stellar Sets shape and evolution of galaxy stellar
mass function.mass function.
SFR-MSFR-M**: Close : Close but no cigarbut no cigar
Models get right:Models get right: SlopeSlope ScatterScatter General evolutionGeneral evolution
But But amplitude amplitude evolution is evolution is wrong!wrong!
Data has higher Data has higher SFR at given M*.SFR at given M*.
But wait… cold But wait… cold accretion sets accretion sets maximum maximum rate!rate!
RD 08
•Green: Millenium SAM •Red, magenta: SPH sims •Blue: Data (=0.3)
Birthrate evolution: Huh?Birthrate evolution: Huh?
Discrepant during the peak dusty SF epoch.Discrepant during the peak dusty SF epoch. Something different? Calibrations? IMF?Something different? Calibrations? IMF?
Gonzalez+ 10
Simulations
RD 08
SummarySummary 3 regimes of cosmic SFH: Early growth (z>4),
rapid phase (1<z<4), late decline (z<1) Dominated by fairly smooth, filamentary cold
accretion. Mergers & bursts subdominant. Dust embedded SF peaks @ z~2. Before
that, less dust; after, SF morphology change? Generally, trends well explained by
Cold mode accretion, smooth & filamentary Outflows that eject more mass from small gals.
Mismatch between SFR and M* evolution, both vs. data and theory?
Diff recycling governs GSMF Without wind mode,
GSMF~halo MF (scaled). Wind recycling boosts
higher M* galaxies, flattens GSMF.
Once trecyc > tHubble, reverts to steep slope, modulated by outflows (vzw shallower since ~1/vcirc).
Halo baryonHalo baryoncontentcontent
Winds drive lots of baryons out of halos.
Big galaxies lose baryons early.
MW-like halo today has lost ~½ baryons
Peak SF “efficiency” @ 1013M .
Qualitatively similar to observations.
Winds recycle!Winds recycle! Mwinds >> Mstars
wind ~ 0.2 b ejected ~ 0.5 b Compare: * ~ 0.08 b
Median # ejections: 3
Turnaround radius ~100 physical kpc high-z: Enrich IGM low-z: Halo fountains
Median trecyc ~ 1 Gyr
Constraints from IGM Constraints from IGM enrichmentenrichment Outflows are the only way to enrich IGM z~2-4 CIV absorbers very constraining;
favors momentum-driven wind scalings: vw~vcirc, ~vcirc
-1.
win
d sp
eed
mass loading
Too fewmetals in IGM
IGM too hot
Diffuse IGM unenriched
Too fewmetalsproduced
Momentum-driven wind scalings!
Met
allic
ity
Overdensity
Oppenheimer & RD 2006Oppenheimer & RD 2008Oppenheimer & RD 2009a,b
Gas content fgas(M*) strongly dependent
on outflows. M-D winds keep low-mass
galaxies gas rich by suppressing SF.
Strong outflows make galaxies gas rich, not gas poor.
Galaxies are the antithesis of closed boxes: They process gas as supplied.
Z~M1/3
Mass-Metallicity Mass-Metallicity RelationRelation
z=2
Finlator&RD 08
Conventional thinking: Zgas reflects stage of processing Galaxies lose metals based on .
NO! Why? Outflows are greedy & destructive: They don’t share their energy --
they blow holes!
Analytic 3D simulation
“Wind mode” accretion
Differential RecyclingDifferential Recycling ttrecyclingrecycling goes inversely with mass goes inversely with mass
680 km/s
340 km/s
vw~vcirc
Luminosity functionsLuminosity functions z~6: Large SF
suppression. Rapid consumption
must eject gas. Macc = M*+Moutflow
SFR (1+)-1
z~2-4: Const ~2+ ~ vc
-1 ~1.7 z=0: Faint end slope
~1.3; less steep! (bright end?…fugly)
Data: Bouwens etel 06Models: =0.3, 8=0.9
RD, Finlator, Oppenheimer 06
DLA Kinematics: Outflows?DLA Kinematics: Outflows? Wide separation (v>vrot) DLAs hard to produce;
protogalactic clump infall fails (eg Pontzen etal). Momentum-drive winds puff out gas, produces wide-
separation systems.Prochaska & Wolfe 01
KS test probno winds, 8e-5
constant winds, 0.037
MD winds, 0.51
No winds Mom-driven windsConstant winds
S. Hong, Katz, RD etal, in prep
Feedback Feedback TomographyTomography
Background sources Background sources observe outflows in observe outflows in action.action.
Tough now, but will Tough now, but will become routine at become routine at z~2+ in 30m era.z~2+ in 30m era.
COS enables at z<1COS enables at z<1 Also possible in Also possible in
emission around emission around galaxies.galaxies.
The next frontier of The next frontier of observational galaxy observational galaxy formation!formation!