Evidence for Feedback in the IGM at High Redshift

Evidence for Feedback in the IGM at High Redshift

Barlow (CIT), Becker (CIT), Boksenberg(IoA),

Sargent (CIT), Simcoe (MIT), Rauch (OCIW)

(based on QSO absorption line data from Keck HIRES, ESI and LRIS)(based on QSO absorption line data from Keck HIRES, ESI and LRIS)

How does the undisturbed IGM look ?

A cosmic web of baryons formed A cosmic web of baryons formed mainly by gravitational instabilitymainly by gravitational instability

Main observational manifestation: Main observational manifestation: the Lyman alpha forestthe Lyman alpha forest

Cen & Ostriker et al Cen & Ostriker et al

Keck HIRESKeck HIRES

Interactions between Galaxies and the IGMInteractions between Galaxies and the IGM

GalaxiesGalaxies

• accrete gas (infall velocities ~ 100 km/s)

• merge (approaching c.o.m. with velocities ~ 200km/s)

• interact tidally, lose gas by ram pressure stripping

• move about, stir and heat the IGM ( T ~10^7 K)

• may have strong winds (outflows w. many 100 km/s)

• chemically enrich the IGM

• produce ionizing radiation

• accrete gas (infall velocities ~ 100 km/s)

• merge (approaching c.o.m. with velocities ~ 200km/s)

• interact tidally, lose gas by ram pressure stripping

• move about, stir and heat the IGM ( T ~10^7 K)

• may have strong winds (outflows w. many 100 km/s)

• chemically enrich the IGM

• produce ionizing radiation

z=4

z=3

z=1.8Boxsize 2 Mpc comov; vc=200km/s; Steinmetz (sim.)

gas phases in a hypothetical large scale filamentgas phases in a hypothetical large scale filament

100 kpc100 kpc

Observable EffectsObservable Effects

1. Metal enrichment: how much, when, how ?

2. Ionization: stellar/AGN ?

3. Signatures of in/outflows

4. Bulk motion and turbulence

5. Accretion vs winds

1. Metal enrichment: how much, when, how ?

2. Ionization: stellar/AGN ?

3. Signatures of in/outflows

4. Bulk motion and turbulence

5. Accretion vs winds

By z~3 the IGM is widely enriched with metals (C,O)By z~3 the IGM is widely enriched with metals (C,O)

Lognormal distribution with

75.085.2/ HO

– describes metallicity of about 50% of the mass and 5% of the volume of the universe

– probes down to overdensities > 1.6, i.e., to the edge of large scale filaments

(Simcoe, Sargent & Rauch 2004)(Simcoe, Sargent & Rauch 2004)

See talk by Joop SchayeSee talk by Joop Schaye

Latest results (Simcoe et al 2004):Latest results (Simcoe et al 2004):

The ‘Ultimate Closed Box’ model (Simcoe et al 2004)

Universal chemical evolution:

treat galaxies as sources of metals and the IGM as the mass reservoir

requires that on average

more than 14 % of a galaxy’s metals must be lost to the IGM to explain the observed IGM metallicity

The effect of the galactic radiation field least explored aspect of feedback: highly important for reionization but

observational evidence difficult to obtain.

Idea: different spectral shapes of the ionizing radiation produce different ratios among common metal ions

• strong CIV metal absorption systems (interior of LSS filaments, outer halos) are ionized by a stellar radiation field (T~40,000 K)

(Boksenberg, Sargent & Rauch 1998,2003)

• matching observed relative C and O metallicities in the IGM to those of metal-poor stars ([C/O]= -0.5) requires soft (stellar) radiation field

(Simcoe et al 2004)

Signatures of Bubbles and Winds in the ISMSignatures of Bubbles and Winds in the ISM

UVH

30 Dor (LMC); Wang 1999

Xray

• “spherical”, expanding shells

• compressed, shocked gas

• hot interior (10^6 K)

• transitory, cooling zone (OVI; 10^5 K)

• cool dense layer (MgII; few x 10^4 K)

• collisional + photoionization

• “spherical”, expanding shells

• compressed, shocked gas

• hot interior (10^6 K)

• transitory, cooling zone (OVI; 10^5 K)

• cool dense layer (MgII; few x 10^4 K)

• collisional + photoionization

Probe ISM gas with multiple lines of sight to lensed QSOs

A possible galactic HI shellA possible galactic HI shell

MgIIMgII absorption system at z~0.56absorption system at z~0.56

Curious two-component structure Curious two-component structure coherent over ~1kpc :coherent over ~1kpc :

LoS intersecting two bubble walls ?LoS intersecting two bubble walls ?

Do high z winds manage to get out of galaxies ?

Two approaches:Two approaches:

1.1. look directly into galaxies and their immediate neighbourhoodlook directly into galaxies and their immediate neighbourhood

- learn about individual winds, connection of winds and stelpops.- learn about individual winds, connection of winds and stelpops.

2. look at random places in spaces and do a blind search for winds2. look at random places in spaces and do a blind search for winds

- learn about global statistics of winds- learn about global statistics of winds

(Pettini et al 2000)(Pettini et al 2000)

Lyman break galaxies have outflows with Lyman break galaxies have outflows with several 100 km/s, similar to present day several 100 km/s, similar to present day superwindssuperwinds

Can we observe winds outside of galaxies ?

A lack of neutral hydrogen within 0.5 A lack of neutral hydrogen within 0.5 comoving Mpc from those objects may comoving Mpc from those objects may correspond to wind-blown cavitiescorrespond to wind-blown cavities

(Adelberger et al 2003)(Adelberger et al 2003)

• shock heated (collisionally ionized) gasshock heated (collisionally ionized) gas

• large, rapidly expanding shell structureslarge, rapidly expanding shell structures

• metal enriched gasmetal enriched gas

KT 1010

75~

2. Search the IGM directly for2. Search the IGM directly for

use OVI ion as a tracer of galactic windsuse OVI ion as a tracer of galactic winds

OVI survey at z ~2.5 with Keck HIRES (Simcoe et al 2002)OVI survey at z ~2.5 with Keck HIRES (Simcoe et al 2002)

1

exp1000100~ v kms

Z10 Z -2.8

Evidence for symmetric in/outflow: (Simcoe et al 2002)

~ ¼ of strong OVI absorbers show conspicuous double component structure in HI and other ions. Shocked shell ? Bi-polar outflow ?

OVI

HI Ly alpha

HI Ly alpha

OVI

Temperatures of OVI, CIV and SiIV

KOVIT 5102)(

If line widths predominantly If line widths predominantly thermal,thermal, the median the median temperature of the OVI phase istemperature of the OVI phase is

whereaswhereas

Simcoe et al 2002Simcoe et al 2002

KSiIVCIVT 4104),(

Probably shocked gas or thermal Probably shocked gas or thermal conduction in a hot bubbleconduction in a hot bubble

Properties of OVI systems

High metallicity 49.1/ HO

82.2/ HC

as opposed to average metallicity in the IGM,

Sizes L ~ 60 kpc, densities 3010~/

(Simcoe et al 2002)(Simcoe et al 2002)

Number density and cross section from rate of incidence per unit redshift

0.117.

2

kpc

R

Mpcprop

n3

If all bright Ly break galaxies had such an OVI halo around them (with If all bright Ly break galaxies had such an OVI halo around them (with comov. density ; Adelberger & Steidel 2000): comov. density ; Adelberger & Steidel 2000):3004.0

Mpc

At z = 2.5 At z = 2.5 Lybreak galaxiesLybreak galaxies could account for could account for all of the all of the observed OVI absorptionobserved OVI absorption in the Simcoe et al survey if they are in the Simcoe et al survey if they are embedded in embedded in hot bubbles out to radii ~ 40 kpchot bubbles out to radii ~ 40 kpc

Summary: Highly ionized (OVI) Gas Summary: Highly ionized (OVI) Gas (Simcoe et al 2002)(Simcoe et al 2002)

• OVI kinematically distinct from and hotter than other gas phases (CIV)OVI kinematically distinct from and hotter than other gas phases (CIV)

shocked gas ?shocked gas ?

• peculiar double component structure relatively common in strongest peculiar double component structure relatively common in strongest systems. systems. shells or cones ?shells or cones ?

• sizes a few tens of kpc, overdensities around 10 – 30 (as opposed to > sizes a few tens of kpc, overdensities around 10 – 30 (as opposed to > 100 for strong CIV/SiIV systems). 100 for strong CIV/SiIV systems).

external to galaxiesexternal to galaxies

• Metallicity [O/H] > -1.5 higher than general IGMMetallicity [O/H] > -1.5 higher than general IGM

outflow, as opposed to infalloutflow, as opposed to infall

• cross-section consistent with R~ 40 kpc hot bubbles around Lyman break cross-section consistent with R~ 40 kpc hot bubbles around Lyman break galaxies galaxies

Kinematic effects of feedback:

Bulk motion and turbulence in the IGM

Kinematics of the IGM

Probe bulk motion and turbulence with multiple lines of sight:

Lensed QSO

IGM

observer

grav. lens

Velocity and column density differences as a function of spatial scale, density

Becker et al 2004Becker et al 2004

Spatial coherence and kinematics in the IGMSpatial coherence and kinematics in the IGM

sep ~ 0.22 kpcsep ~ 0.22 kpc

sep ~ 260 kpcsep ~ 260 kpc

Expect:

Large scale motion represent Hubble expansion

Small scale motion are hydrodynamic disturbances (e.g., winds)

Large Scale Velocity Shear in the IGMLarge Scale Velocity Shear in the IGM

Differences between the velocities of the same absorber in two lines Differences between the velocities of the same absorber in two lines of sight separated by S:of sight separated by S:

• On On kpc scaleskpc scales, velocity shear consistent with , velocity shear consistent with zerozero..

• On On large scales (250 kpc)large scales (250 kpc) , , a significant velocity a significant velocity shear (~ 30km/s RMS) shear (~ 30km/s RMS) is visible. is visible.

• Its distribution can be reproduced assuming the Its distribution can be reproduced assuming the clouds are randomly orientated, freely expanding clouds are randomly orientated, freely expanding slabs. slabs.

kpcS 1.1

kpcS 250

Is the large scale motion consistent with the Hubble flow ?

Adopting a coherence length ~500 physical kpc (e.g., D’Odorico etal 1998), Adopting a coherence length ~500 physical kpc (e.g., D’Odorico etal 1998),

expansion velocity is about 70 % of Hubble flowexpansion velocity is about 70 % of Hubble flow..

Not clear whether one should expect to find clouds to follow Hubble flow Not clear whether one should expect to find clouds to follow Hubble flow exactly (column density limited sample, crude modelling, observational errors) exactly (column density limited sample, crude modelling, observational errors)

The Lyman alpha forest on kpc scalesas seen in two Lines of sight towards RXJ0911+0551 (z=2.80)

2.2 kpc

“0” kpc

degree of disturbances among two lines of sight degree of disturbances among two lines of sight

tells us about filling factor of windstells us about filling factor of winds

38L

upper limit on the upper limit on the volume filling factorvolume filling factor of ‘winds’: of ‘winds’:

Mechanical luminosityMechanical luminosity

gas densitygas density 5n

e.g., winds starting at z~4 cannot fill more than 18% of the volume.e.g., winds starting at z~4 cannot fill more than 18% of the volume.

(Rauch et al 2002)(Rauch et al 2002)

General low density IGM at z~3General low density IGM at z~3

• Large scale motions consistent with full Hubble Large scale motions consistent with full Hubble expansionexpansion

• Most of the intergalactic medium (by volume) is highly Most of the intergalactic medium (by volume) is highly homogeneous on kpc scales.homogeneous on kpc scales.

• The volume filling factor for strong winds arising later The volume filling factor for strong winds arising later than z~4 is less than 18% (possibly much less). than z~4 is less than 18% (possibly much less).

• Low density Lyman alpha forest probably well described Low density Lyman alpha forest probably well described by numerical simulations with finite resolution and by numerical simulations with finite resolution and without any feedback (without any feedback (but see metal absorption systemsbut see metal absorption systems))

Going to higher density regions…Going to higher density regions…

Spectra of UM673 A (red) and B (black)(z(QSO) = 2.72, sep. =2.24”)

metals !metals !

metals !

metals !

r = 480 pc

z~z(QSO); r = “0” pc

Traces of galactic winds in higher density, metal enriched CIV gas ?Traces of galactic winds in higher density, metal enriched CIV gas ?

Origin of velocity differences, spatial scales ?

~

a few – 200; velocity width < 300 km/sa few – 200; velocity width < 300 km/s

characteristic of the filamentary matrix in which characteristic of the filamentary matrix in which galaxies are embeddedgalaxies are embedded

VV BAV

V

Measure differences between lines of sight A and B as a Measure differences between lines of sight A and B as a function of transverse separation between the LoS:function of transverse separation between the LoS:

Column density weighted projected velocity:Column density weighted projected velocity:

transverse separation (kpc)transverse separation (kpc)

Fractional difference in column density:Fractional difference in column density:

NNNN

BA

BAN

max N

Results:Results:

• minimum size of CIV clouds (a few 100 pc)minimum size of CIV clouds (a few 100 pc)

• increasing velocity shear (70km/s @ 10 kpc)increasing velocity shear (70km/s @ 10 kpc)

V V2

What Does It Mean ?

or are measures of the turbulence of the gas on a spatial scale r, and of the rate of energy input, .

E.g., for Kolmogorov case,

rV r 3/22

A crude estimate of the energy transfer rate A crude estimate of the energy transfer rate from our data:from our data:

scm323

10~

i.e., the turbulent energy in CIV gas is much i.e., the turbulent energy in CIV gas is much less than for an actively starforming region less than for an actively starforming region (e.g., factors 100 -1000 less than for Orion).(e.g., factors 100 -1000 less than for Orion).

There is a finite amount of turbulent energy in the gas.

Defines a dissipation time scale (time it takes to transform the mean kinetic energy in the gas, at a rate into heat),

years.

The finite size of the CIV clouds defines relaxation time scale:

Without further energy input, pressure and density differences are wiped out by pressure waves during a sound crossing time :

years.

Structure on larger scales has not been wiped out

there is (at least intermittent) energy input into the gas.

diss

v2

2

1

s

skm

cspc

rr

css 120300~

17

104.1

109v 7

2

~2

1~ diss

Origin of the turbulence ?Origin of the turbulence ?Gas may have been stirred by mergers/tidal interactions or Gas may have been stirred by mergers/tidal interactions or

winds, or it may just be circling the drainwinds, or it may just be circling the drain

Timescales are similar to those of recurrent star formation events that have been Timescales are similar to those of recurrent star formation events that have been postulated for various environments:postulated for various environments:

• z~1 field galaxies (Glazebrook et al 1999)

• the Galaxy (Rocha-Pinto et al 2000)

• fluctuations in SFR in nearby spirals (Tomita et al 1996; Hirashita & Kamaya 2000)

• galactic nuclei (Krugel & Tutukov 1993)

• Lyman break galaxies (Papovich, Dickinson & Ferguson 2001)

CIV absorption from the filamentary LSS structure

SPH modelling of pre-enriched gas SPH modelling of pre-enriched gas undergoing gravitational collapse undergoing gravitational collapse reproduces all know properties of CIV reproduces all know properties of CIV systems systems

(except clustering – box too small)(except clustering – box too small)

Distribution of CIV line widthsDistribution of CIV line widths(thermal + turbulent) (thermal + turbulent)

Rauch, Haehnelt & Steinmetz 1997Rauch, Haehnelt & Steinmetz 1997

““structure function” of structure function” of the universe the universe

101.0~

2007~

Velocity-density-scale diagram

Summary: evidence for feedback in the IGM ?Summary: evidence for feedback in the IGM ?• Cosmic web widely metal enriched down to mean densityCosmic web widely metal enriched down to mean density

• CIV metal absorbers ionized by local stellar radiation fieldCIV metal absorbers ionized by local stellar radiation field

• General low density IGM (the universe by volume) kinematically undisturbed General low density IGM (the universe by volume) kinematically undisturbed by feedbackby feedback

• kinematic disturbances in the somewhat denser CIV gas; low level kinematic disturbances in the somewhat denser CIV gas; low level (intermittent) energy input; filamentary gas possibly stirred by galaxy motions, (intermittent) energy input; filamentary gas possibly stirred by galaxy motions, winds, circling the drainwinds, circling the drain

• Double component structure, temperatures, expansion velocities, and the Double component structure, temperatures, expansion velocities, and the high metallicity seen in some MgII (low ionization, dense gas) and OVI (high high metallicity seen in some MgII (low ionization, dense gas) and OVI (high ioniz., tenuous hot gas) point to ISM and IGM windsioniz., tenuous hot gas) point to ISM and IGM winds

• velocities and ionization structure around high z starburst gals. consistent with velocities and ionization structure around high z starburst gals. consistent with superwindssuperwinds

• Inevitable that some of the “wind” phenomena described here are not due to Inevitable that some of the “wind” phenomena described here are not due to winds but to gravitationally induced heating, motions,strippingwinds but to gravitationally induced heating, motions,stripping

• To date origin and and timing of most of the metal enrichment unclear; To date origin and and timing of most of the metal enrichment unclear; probably early (z>5) and by dwarf galaxiesprobably early (z>5) and by dwarf galaxies

When does the wide spread metal enrichment happen ?When does the wide spread metal enrichment happen ?

E.g., E.g.,

Early vs. late (ongoing) enrichment

Massive vs. dwarf galaxies

Gravitational vs. winds

• ambient universe much denser at high z, ram pressure from infalling ambient universe much denser at high z, ram pressure from infalling gas favors winds from dwarfs (e.g., Fujita et al 2004)gas favors winds from dwarfs (e.g., Fujita et al 2004)

• mass-metallicity relation may indicate mass loss to IGM dominated mass-metallicity relation may indicate mass loss to IGM dominated by dwarf galaxies (Tremonti et al 2004) by dwarf galaxies (Tremonti et al 2004)

• quiescence of Lyman alpha forest, ubiquity of metals appears to quiescence of Lyman alpha forest, ubiquity of metals appears to favour early, widespread (= dwarf?) enrichment, ongoing locally (OVI favour early, widespread (= dwarf?) enrichment, ongoing locally (OVI winds, CIV turbulence)winds, CIV turbulence)

Gravitational motionGravitational motion(accretion,tidal,merging)(accretion,tidal,merging)

winds

quiescence of general IGM consistent can’t be important

CIV turbulence consistent ? consistent ?

OVI systems temperatures consistent consistent

OVI kinematics (double components)

accretion shock wind shell

High OVI metallicity stripping of ISM metal rich winds

Depletion of HI @ Ly break gals. Ionized by accretion

shock, cluster radiation

blown away by wind

Gravitational effects vs. winds ?Gravitational effects vs. winds ?

Case I: possible old SN remnant at z = 3.62Case I: possible old SN remnant at z = 3.62

M

cm3

• Radius 13 < R < 48 pc

• thickness (LoS): 0.015 < L< 1.6 pc

•Mass range 0.4 < M < 2700

•Expansion velocity v > 195 km/s

•Number density 0.2 < n < 2

• metallicity

• age ~ 10,000 years

~Z Z

Interactions between Galaxies and the IGMInteractions between Galaxies and the IGM

GalaxiesGalaxies

• accrete gas (infall velocities ~ 100 km/s)

• merge (approaching c.o.m. with velocities ~ 200km/s)

• interact tidally, lose gas by ram pressure stripping

• move about, stirring and heating the IGM ( T up to 10^6 K)

• may have strong winds (outflows w. many 100 km/s)

• produce ionizing radiation

• accrete gas (infall velocities ~ 100 km/s)

• merge (approaching c.o.m. with velocities ~ 200km/s)

• interact tidally, lose gas by ram pressure stripping

• move about, stirring and heating the IGM ( T up to 10^6 K)

• may have strong winds (outflows w. many 100 km/s)

• produce ionizing radiation

‘‘Structure function’ of the universeStructure function’ of the universe

Evidence for individual winds ?Evidence for individual winds ?

General low density IGM at z~3General low density IGM at z~3

• Large scale motions consistent with full Hubble expansionLarge scale motions consistent with full Hubble expansion

• Most of the intergalactic medium (by volume) is highly Most of the intergalactic medium (by volume) is highly homogeneous on kpc scales.homogeneous on kpc scales.

• The fraction of the Lyman alpha forest disturbed by more than 5% in The fraction of the Lyman alpha forest disturbed by more than 5% in optical depth is < 23% (very conservative)optical depth is < 23% (very conservative)

• The volume filling factor for strong winds arising later than z~10 is The volume filling factor for strong winds arising later than z~10 is less than 20% (possibly much less). less than 20% (possibly much less).

• Low density Lyman alpha forest probably well described by Low density Lyman alpha forest probably well described by numerical simulations with finite resolution and without any numerical simulations with finite resolution and without any feedback (feedback (but see metal absorption systemsbut see metal absorption systems))

The Silence of the Lines:The Silence of the Lines:

Translate column density into baryon density fluctuations, Translate column density into baryon density fluctuations, making use of tight correlationmaking use of tight correlation

barHIN )(

Obtain RMS scatter of the baryon overdensity:Obtain RMS scatter of the baryon overdensity:

NN BA logloglog222

For a beam separation of 110 pc proper, and a sample of unsaturated For a beam separation of 110 pc proper, and a sample of unsaturated Lyalpha forest lines with 12<logN<14.13, Lyalpha forest lines with 12<logN<14.13,

the RMS fluctuations in the baryon density are less than about 3 %.the RMS fluctuations in the baryon density are less than about 3 %.

Similarly, RMS velocity differencesSimilarly, RMS velocity differences !!! !!! smBA VV /4002

What about What about large scale motionslarge scale motions ? ?

Consistent with Hubble flow ?Consistent with Hubble flow ?

Peculiar velocities ?Peculiar velocities ?

Signs of feedback (winds) ?Signs of feedback (winds) ?

Define ‘disturbed fraction of the Lyalpha forest’ = fraction of the spectrum where the optical depths differ by more than a certain amount

23.0fLoS

005|| BA

Measure

,12 2

22

zHnDn

vRcRf fwhms

LoS

Where is the width of the spectroscopic ‘footprint’ of a wind bubble intersecting a line of sight (two thermally broadened absorption lines from a crossing shell). and are the radius and expansion velocity of the shell, and is the space density of the sources of the wind events.

Adopt a model for and (e.g., superbubble model of Mac Low & McCray 1988 and solve for .

fLoS

zHD v fwhm/2

R R

n

n

R R

upper limit on the upper limit on the number density of number density of

galaxiesgalaxies producing ‘winds’: producing ‘winds’:

upper limit on the upper limit on the volume filling factorvolume filling factor of of ‘winds’:‘winds’:

There is a finite amount of turbulent energy in the gas.

Defines a dissipation time scale (time it takes to transform the mean kinetic energy in the gas, at a rate into heat),

years.

The finite size of the CIV clouds defines another time scale:

Without further energy input, pressure and density differences are wiped out by pressure waves during a sound crossing time :

years.

Structure on larger scales has not been wiped out

there is (at least intermittent) energy input into the gas.

diss

v2

2

1

s

skm

cspc

rr

css 120300~

17

104.1

109v 7

2

~2

1~ diss

(Pettini et al 2000)(Pettini et al 2000)

Lyman break galaxies have outflows with Lyman break galaxies have outflows with several 100 km/s, similar to present day several 100 km/s, similar to present day superwindssuperwinds

Can we observe winds outside of galaxies ?

A lack of neutral hydrogen within 0.5 A lack of neutral hydrogen within 0.5 comoving Mpc from those objects may comoving Mpc from those objects may correspond to wind-blown cavitiescorrespond to wind-blown cavities

(Adelberger et al 2003)(Adelberger et al 2003)

Low vs. high mass gals. as the origin of metals in the IGM

Evidence in favor of massive galaxies:

• superwinds at low z blow out of galaxies (e.g., Heckman 2001), and strong winds seen in Lyman break galaxies (Pettini et al 2000)

• Lack of neutral hydrogen around high z starburst galaxies (Adelberger et al 2003)

• superwinds grafted onto massive galaxies in large scale cosmological hydro-simulations manage to get the metals out

Evidence in favor of dwarf galaxies:

• high resolution simulations of winds: infall and high density of the IGM at high z favor dwarf galaxies outflows (e.g., Fujita et al 2004)

• z~0.1 mass-metallicity relation (Tremonti et al 2004): mass loss dominated by low mass galaxies.

• Lack of neutral hydrogen around starburst galaxies (Adelberger et al 2003) may have explanations other than winds (hot, highly ionized gas from accretion; photoionization by cluster radiation field).

(Pettini et al 2000)(Pettini et al 2000)

Spectra of massive high z starburst galaxies have Spectra of massive high z starburst galaxies have outflow features similar to present day superwindsoutflow features similar to present day superwinds

winds linked to individual galaxies

A lack of neutral hydrogen within 0.5 comoving Mpc A lack of neutral hydrogen within 0.5 comoving Mpc from those objects may correspond to wind-blown from those objects may correspond to wind-blown cavitiescavities (Adelberger et al 2003)(Adelberger et al 2003)

But: But:

• ambient universe much denser at high z, ram ambient universe much denser at high z, ram pressure from infalling gas favors winds from dwarfs pressure from infalling gas favors winds from dwarfs (Fujita et al 2004)(Fujita et al 2004)

• mass-metallicity relation indicates mass loss to IGM mass-metallicity relation indicates mass loss to IGM dominated by dwarf galaxies (Tremonti et al 2004) dominated by dwarf galaxies (Tremonti et al 2004)

But: But:

May have alternative explanations: merger-heated May have alternative explanations: merger-heated halo, cluster radiation field halo, cluster radiation field

Anecdotal evidence for the existence of ISM shells ok, but objects are much smaller and weaker than required for wind bubbles that leave the galaxy.

• Too quiescent to be directly Too quiescent to be directly related to starformationrelated to starformation

• residual turbulence and finite residual turbulence and finite cloud sizes suggest ongoing (at cloud sizes suggest ongoing (at z~3) low level, energy input on z~3) low level, energy input on timescales ~ 10-100 Mio years.timescales ~ 10-100 Mio years.

• Time scales are similar to those Time scales are similar to those involved in recurrent involved in recurrent starformation events. Winds or starformation events. Winds or galaxy encounters (accretion, galaxy encounters (accretion, mergers, stripping) may play a mergers, stripping) may play a role.role.

CIV Gas:

““structure function” of structure function” of the universe the universe

101.0~

2007~