feedback at high redshift

Feedback at High Redshift

Alice Shapley

(UC Berkeley)

May 4th, 2004

Overview and Motivation

• Importance of feedback

• Observations at z~3: winds and ionizing radiation

• Observations at z~2: more winds, the smoking gun

• What’s next: morphologies, ages, masses, z~1

High-res QSO spectra plus large galaxy samples serve as a powerful tool for understanding feedback during an important epoch of the Universe’s history

Schematic model of superwinds

• Collective effect of multiple SNe: mechanical energy input causes shock-heated expanding superbubble with T~108 K, expands, entrains cold ISM

• Superwind seen in local starbursts with >0.1 Msun/year/kpc2

(Heckman et al. 1990, Heckman 2002)

Outflows: Local Starbursts

M82• Nearby starburst galaxy

• Red is H emission from ionized gas above the plane of the galaxy

• outflow speed: >500 km/s

• plenty of detailed spatial information

(Subaru Image)

Importance of feedback/outflows

• Enrichment and heating of IGM

• Enrichment and entropy floor in ICM

• Problems in models of galaxy formation: overcooling and angular momentum

• Feedback often invoked as solution, but crudely modeled in both semi-analytic and numerical codes

• Observationally important to constrain mass, energy, metals escaping, and how these depend on galaxy properties

Observational Constraints on Feedback at High Redshift

Feedback at z~3

Typical L* LBG Spectrum

Unsmoothed Smoothed by 5 pix

RAB=24-25.51.5 hr exposure S/N ~ 2/pix, 9-12 AA resolution

Evidence for outflows in spectra

Velocity offsets (em-abs)

• Redshifted Ly

• Blueshifted IS abs

• Avg offset is 650 km s-1 (z=0.008) outflow

• Stellar photospheric features are too weak to detect, so we need to guess what the systemic redshift is

(Shapley et al. 2003)

Total LBG Composite Spectrum

Features• UV cont: O & B stars

• Stellar: photospheric and wind

• Outflow-related: Ly (v=+360), low and high ions (v=-170)

• Nebular emission

• Fine-structure emission


Empirical Outflow Results

• Stronger Ly • Bluer UV continuum• Weaker low-ion absorption• Smaller v(em-abs)

• Dependence of low- and high-ions decoupled

z~3 Galaxy/IGM Connection

Unsmoothed

• 8 fields with QSOs at z~3.5

• Survey galaxies and Ly forest in same cosmic volume

• Determine relative distributions of galaxies, HI, metals

(Adelberger et al. 2003)

z~3 Galaxy/IGM Connection

Deficit of HI near LBGs and strong LBG/CIV cross-correlation function (Adelberger et al. 2003)

less HI

more HI

A Physical PictureOutflows of neutral and ionized gas:

different neutral and ionized covering fractions?

Hotter gas we don’t see

What radius?

A Physical PictureDust:

UV extinction in outflow

Outflow geometry vs. what is seen in local superwinds

A Physical PictureEffect on IGM:

Gal/IGM correlations -->

Expected sphere of influence: 180 kpc (0.5-1 comoving Mpc)

Vwind >= vesc

The Search for Lyman-Continuum Emission

• Ionizing background: important for understanding reionization and Ly forest props; measured with QSO “proximity effect”

• Question: relative contribution of QSOs & gals vs. z??? (drop-off in QSO number density at high redshift)

•Lyman-Continuum Observations of Galaxies

• z~0: HUT spectra at z~0, fesc<0.01-0.15 (Leitherer et al.)

• z=1.1-1.7:HST/STIS UV imaging, fesc <0.002 (Malkan et al.)

• z~3: LBG composite spectrum, fesc~0.10 (Steidel et al.)

• Controversy at z~3!!

• HST/WFPC2 UBVi colors, fesc <0.039 (Fernandez-Soto et al.)

• VLT spectra of 2 gals, fesc<0.01 (Giallongo et al. 2002)

Detection of Ly-C Emission?Lyman Cont. Leakage

• 29 gals at <z>=3.4+/-0.09

• Significant Ly-cont flux in composite spectrum 5 times more ionizing flux than QSOs at z~3

• Bluest quartile in (G-R)0, strong Ly emission, IS abs lines weaker than cB58: is it representative?

• fesc different from local SB (Leitherer et al. 1995)(Steidel et al. 2001)

The Search for Lyman-Continuum Emission

• Ionizing background: important for understanding reionization and Ly forest props; measured with QSO “proximity effect”

• Question: relative contribution of QSOs & gals vs. z??? (drop-off in QSO number density at high redshift)

•Ly-C Observations of Galaxies

• z~0: HUT spectra at z~0, fesc<0.01-0.15 (Leitherer et al.)

• z=1.1-1.7:HST/STIS UV imaging, fesc <0.002 (Malkan et al.)

• z~3: LBG composite spectrum, fesc~0.10 (Steidel et al.)

• Controversy at z~3!!

• HST/WFPC2 UBVi colors, fesc <0.039 (Fernandez-Soto et al.)

• VLT spectra of 2 gals, fesc<0.01 (Giallongo et al. 2002)

New Ly-C Observations

• Spectra with 18+ hours of exp time for a sample of ~15 objects

• Red side: detailed observations of interstellar lines

• Blue side: sensitive observations of Lyman Continuum region

• Overcome some of the limitations of composite spectra

• Observations approach the quality of cB58, but larger sample

We may detect Ly-C emission for an individual object!

SSA22a-D3 z=3.07 Rs=23.37

P200 Rs HST/NICMOS F160W

2”

SSA22a-D3 z=3.07 Rs=23.37HST/NIC F160W

Keck/LRIS-B, 8 hours

Red side: strong abs lines

Blue side: Ly to atm cutoff

D3 is double, and upper brighter component appears to have significant flux below 912 AA

Lyman limit, 912 AA Ly

4950 AA 3710 AA

SSA22a-D3 z=3.07 Rs=23.37HST/NIC F160W Ly-C Ly Ly

Apparent detection of flux at rest-frame 880-912 AA (S/N~7). Other pair member is undetected.

SSA22a-D3 z=3.07 Rs=23.37HST/NIC F160W Ly-C Ly Ly

D3 is only object with apparent Ly-C flux out of 15 on mask. Why is it special?

Evolution of the Ly Forest• dn/dz governed by balance between ionizing bg (ionization) and Hubble expansion (recombination)

•At 1.5<z<4, dn/dz~(1+z)2.47

• At lower-z, dn/dz shallower (decrease in QSO density)(Kim et al. 2002)

Feedback at z~2

z>2 color-selection

• Adjust z~3 UGR crit. for z~2 (Adelberger et al. 2004) • Spectroscopic follow-up with optimized UV-sensitive setup (Keck I/LRIS-B) (Steidel et al. 2004)

Redshift Distributions

Unsmoothed

LBG: z~3 (940)

BX: z=2-2.5 (749)

BM: z=1.5-2.0 (107)

700 gals at z=1.4-2.5

5/7 survey fields contain bright bg QSOs

(Steidel et al. 2004)

Evidence for outflows in spectra

• Outflow kinematics

• Ly em at systematically higher redshift than IS abs

• observed in both z~2 and z~3 LBGs

• part of the gal/IGM connection

z~3 vs. z~2 outflow kinematics

Unsmoothed

• v=0 from rest-frame optical nebular emission lines: [OIII] at z~3 and H at z~2

• ISM kinematics similar at z~3 and z~2

• Typical velocities are 200-400 km/s wrt nebular emission lines

• (Ly-abs)=500-1000 km/s


z~3

z~2

z~2 Galaxy/IGM Connection•Much higher galaxy surface density (factor of 4 higher per unit solid angle)

–Further explore use of galaxy spectra to probe IGM

–Forest evolves extremely rapidly over the redshift range 3.51.8: how does the galaxy/forest relationship change?

•Many more QSO sightlines

–17 lines of sight in 5 fields

• Simultaneously obtain first extensive information on z~2 galaxies.

–Epoch of peak star formation and black hole growth?

–Redshifts z=1.9-2.6 are ideal for near-IR spectroscopic follow-up

Q1623: QSOs, gals at z=1.8-2.5

7 QSO probes (HIRES/ESI/LRIS-B spectra) in 16’ by 12’ field

z~2 Galaxy Proximity Effect?

(yellow:Adelberger et al. 2004, blue:simulations by Kollmeier and Weinberg)

z~2: 22 gals w/in 0.8h-1 comoving Mpc of QSO sightline

Less HI More HI

z~3 z~2

Less HI

More HI

The “Smoking Gun”

Q2343-BX587

• Bright bg QSO: z=2.52

• BX587: z=2.24, R=24, Ks=20.3, D=115 kpc

• Blue circles have 30”/60” (235/470 kpc)

Direct association between gals and broad OVI, NV, CIV

The “Smoking Gun”Galaxy Spectra • ∆(vneb-vism) = 460 km/s• O/H~solar• SFR~85 Msun/yr, M*~6 x 1010 Msun

HIRES QSO Spectrum• ∆v(CIV,NV)~570 km/s (wind: shock-heated and then cooling)• Weak associated Ly

zgal

D=115 kpc

OVI

The “Smoking Gun”: OVI

Z=2.44 Z=2.32v=0

is zgal

Galaxy: BX717 z=2.4353

D=218 kpc

Galaxy: MD103 z=2.3148

D=115 kpc

(Simcoe et al. 2002)

Q1700: Direct association between gals and OVI absorption!

Future DirectionsData

Higher spectral resolution obs of strong absorption lines Outflows vs. opt/IR colors (age, stellar mass)Outflows vs. Ly-C leakage (vs. covering fraction)Outflows vs. chemical abundanceGalaxy/galaxy pairs, spatially distinct probes of outflowsOutflow vs. morphology (HST/ACS)Extend similar studies down to z~1 (HST/FOS)

Simulations

What physical state of galaxies determines conditions in outflow? What is geometry of different phases of outflow? How much mass, energy, metals escape?

Spectra vs. Morphology

Spectra vs. Morphology• Combine Morphological and spectral information:

--> extended disk-like, merger, compact

--> Lya em/abs, low- and high-ionization abs

• Attempt to obtain spatial/geometric information about outflows (along with pairs)

• 240 UV-selected galaxies at z>1.4 in GOODS/ACS

-->multi-wave: x-ray, radio, submm, Spitzer

• 50 z~3 galaxies in SSA22a field with GDDS/ACS

Spectra vs. MorphologyKeck/LRIS-B spectrum HST/ACS Bviz

z=2.05; RAB=23.384”


z=2.22; RAB=23.284”


z=2.23; RAB=23.504”

A Special Case: The Pair at z=1.60/2.17

BX201 z=2.17

BM115 z=1.60

HST/WFPC2 F814W image=2” 11 h-1 kpc at z=1.6

Keck/LRIS spectra 3800-4100 AA

• Two UV-selected z~2 galaxies on one slit• Higher z galaxy probes outflow of lower-z gal at 11h-1 kpc• Outflowing gas: velocity & abs strength difference vs. radius

Examples of Deep LBG Spectra• LRIS-R spectra (LRIS-B covers Ly and Lyman continuum)

• Use these spectra to measure physical properties of abs. lines; connect with UV-color, Ly, Lyman continuum

• Obtain complete data set: near-IR imaging (ages) and spectra (O/H), morphologies

Summary• Evidence for SNe feedback & its effect on IGM at z~2-3

• Possible detection of Ly-Cont radiation at z~3

• Next step: determine detailed properties of galaxies sustaining superwinds: morphologies, ages, masses, geometry (how much mass and energy are involved? What determines appearance of spectra/outflow?)

• Combining deep spectroscopic observations with deep ACS images will provide great insight into the nature of feedback, when star-formation, stellar mass build-up, AGN activity were most active in the Universe.

Morphology vs. Outflow props• Use ACS BViz images of GOODS-N field, in which there are 240 galaxies with z>1.4

• Connect morph and spectroscopic outflow props: extended disk-like, merger, compact

• Ind. and avg.Galaxies at z=2.1-2.5


z=2.22; RAB=23.224”


z=2.55; RAB=23.294”


z=2.10; RAB=23.244”


z=2.08; RAB=23.204”

LRIS/NIRSPEC cross-check

• metallicity measured from both rest-UV and rest-optical features

• UV tells you about stellar and outflow Z

• Nebular tells you about HII region Z

• How do they compare?

LRIS/NIRSPEC cross-check

• crucial for measuring the evolution of enrichment in SF galaxies

• Also, since these gals pollute env-ironments, Z necessary for understanding IGM enrichment

Detailed Astrophysics: MS1512-cB58

Keck/ESI R=6000S/N>30

(Yee et al. 1996, Pettini et al. 2000, 2002)

• z=2.73, AB6540=20.41, magnification~30 due to lensing by foreground cluster at z=0.37

• Observations span submm – x-ray

• Stellar population, dust-content, chemical abundance pattern, large-scale velocity field, mass-outflow rate

z~3 LBG Metallicities: R23

LBG nebular O/H ~ 0.1-1.0 Zsun,

2-4 mags brighter than local L-Z relation(Pettini et al. 2001)

[NII]/H ratios: z~2 metallicities• targeted galaxies with bright K, red R-K

• > 50% have super-solar N2 (at z>2!!!!!!). Could’ve detected lower N2

• what are these galaxies?


LBG Spectroscopic Sample

• 811 z~3 LBGs

• Composite spectra

• Increased S/N

• Perfect for studying average properties and trends

• Group by Ly, UV color, v(em-abs), RAB, SFR, z, morph

Measuring Redshifts: z~3

High redshift

• Ly em/abs, IS abs at z>2.5

• At z =1.5-2.5, these features are in the near UV, while strong rest-frame optical emission lines have shifted into the near-IR

z~2 survey and goalsObservations

• 7 Fields: 5 QSO fields, HDF-N, Groth/Westphal

• Optical images and Keck I/LRIS spectra

• P200/WIRC K-band images in 3 fields (J is planned)

• Keck II/NIRSPEC spectra—initially to get systemic z’s

• Multi-wavelength data (X-ray, radio, SIRTF planned) in HDF-N, Westphal, Q1700

Goals

• Clustering, LF, IGM environments

• Detailed galaxy properties

Examples of Deep LBG Spectra

• Weaker low-ion absorption lines

• Note: spectrum with 2 redshifts (top, C47)

Ly Trends: LBG properties

• Broad distribution of Ly EWs

• Range from strong absorption (EW=-100 AA) to strong emission (EW>100 AA)

• Median EW~0 AA

• Only 25% wpuld be flagged by NB excess (EWobs = 80 AA)


LBG Ly Trends

v vs. Ly

• Ly is related to outflow kinematics

• As Ly emission increases, v(em-abs) decreases

• Different relationship in local results




• Ly forest decrement






• Outflow-related: Ly (v=+360), low ions (v=-170)






• Outflow-related: Ly (v=+360), high ions (v=-170)








• Fine-structure emission



• Where is the gas?

• r > 1.6h-1 kpc (abs strength)

• r < 25 h-1 kpc (gal-gal pairs)

A Physical Picture

Star-forming regions:

stellar features, nebular emission lines, r1/2=1.6h-1 kpc


low- and high-ion abs, v<=600km/s

z~2 survey and goalsObservations

• 7 Fields: 5 QSO fields, HDF-N, Groth/Westphal

• Optical images and Keck I/LRIS spectra

• P200/WIRC K-band images in 3 fields (J is planned)

• Keck II/NIRSPEC spectra—initially to get systemic z’s

• Multi-wavelength data (X-ray, radio, SIRTF planned) in HDF-N, Westphal, Q1700

Goals

• Clustering, LF, IGM environments

• Detailed galaxy properties

Metals in the Forest• Metals, traced by CIV, are found in the same regions of space that contain detected LBGs

– Highest N(CIV) systems appear to be one and the same as LBGs (but with R ~150 kpc proper); extent consistent with expected sphere of influence of winds– Even the weakest CIV systems are distributed like the observed LBGs

• Strongly suggests inhomogeneous enrichment of the IGM…and that most or all places that have observable metals have been recently “disturbed” at z~3

Implications of Winds• ICM metals in clusters of galaxies: these are after all the progenitors of rich environments today…

•“Entropy floor” in galaxy clusters?

•Feedback regulates star formation, suppresses subsequent star formation while wind-affected regions cool (~1-2 Gyr)

•Suppress formation of small galaxies within ~200 kpc of large ones?.

•The existence of winds is not surprising—what may be surprising is their strength and the suggestion that relatively massive galaxies (as opposed to dwarfs) may dominate the effects on the IGM, and not all of the effects are confined to very high redshifts (z>>3).

BX1163: z=1.4 RAB=21.8

• Stellar wind lines (CIV, SiIV, HeII) Salpeter IMF, Z=Zsun

• Stellar photospheric line indices Z=Zsun

• IS abs lines, different phases outflow properties

BX1163: Nebular Metallicity

• Stellar wind lines (CIV, SiIV, HeII) Salpeter IMF, Z=Zsun

• Stellar photospheric line indices Z=Zsun

• NIRSPEC H-band spectrum of H and [NII]

• [NII]/H=0.23 Z=Zsun

• Obtain deep spectra for more typical galaxies

(Stay tuned….more NIRSPEC results)

H kinematics: velocity dispersions

• more frequent instance of rotation at z~2 than z~3 (40% vs. 10%)

• growth of disks?

• (v) is 60% larger at z~2 than at z~3

• build-up of mass?

• H vs. [OIII]

(Erb et al. 2003, 2004)

Photometric Pre-selection

• Lyman discontinuity at rest-frame 912 A gives high-z galaxies very distinctive observed UGR colors


v vs. Ly: Explanation

• Ly vs. v: Emission increases with smaller v(em-abs)

• Larger v(em-abs) may reflect larger range of velocities in absorbing gas

• Ly only escapes when further redshifted bigger v(em-abs)

E(B-V)/Ly/Low-ions

E(B-V), Ly, low-ions all connected

• Ly and low-ions more strongly correlated

• E(B-V) dust-corrected SFR

v(em-abs) Trends: SummaryLow ions Ly E(B-V)

3 samples with v=340, 620, 890 km/s• Weaker trends than E(B-V)/Ly/low-ions

• Ly decreases for larger v

Outflow Properties: A Special Example

2 highest S/N LBGs: cB58 & Q0000-D6

• Very different Ly and low-ion EWs, comparable high-ion EW

• Same vFWHM difference in low-ion EW must be neutral covering fraction (Ly-cont leakage)

Low-ionization Linewidths

Measurable differences in low-ionization line-widths

• We know our spectral resolution.

• Spectral resolution is twice as high as in composite spectra

• We will be able to isolate physical parameters of neutral gas

High vs. Low-ionization

Clear difference in high-ion vs. low-ion linewidth

• Two galaxies with the same low-ion strength and linewidth

• Different SiIV linewidths, and possibly centroids

• May tell us something about the different phases of the outflow

Typical L* LBG Spectrum

Unsmoothed Smoothed by 5 pix

RAB=24-25.51.5 hr exposure S/N ~ 2/pix, 9-12 AA resolution

Stellar Systemic Redshifts

Stellar photospheric absorption lines detected for individual galaxies

• Absolute velocity field established on a case by case basis

• Much better than ambiguous v(em-abs)

LBG Ly Trends

4 quartiles of LBG spectroscopic sample, grouped by Ly EW

• Low-ion EW changes by factor of ~3

• High-ion EW stays roughly constant (weaker in sample with strong Ly em)

• Low- and high-ion lines probe outflows


LBG Ly Trends

UV color vs. Ly EWStrong em blue; strong abs red

Monotonic decrease in E(B-V) with increasing Ly em.

Absorbing Gas: CF vs. vFWHM

• Strong correlation between low-ionization lines, Ly and UV color

•What physical parameters govern low-ion EW?• Saturated covering fraction, vFWHM

• Need to know spectral resolution• Obtain intrinsic covering fraction, vFWHM

• Problem: resolution~vFWHM

• Higher spectral resolution necessary (<=250km/s)

Absorbing Gas: Column Density

• MS1512-cB58 (z=2.73) is gravitationally lensed by x30 (high-quality data). N(HI) is fit from spectrum.

• This is the only LBG with a measured N(HI). Can’t do it from composite spectra.

•Assuming geometry, convert N(HI) and v to mass outflow rate

KeckII/ESI spectrum R=6000 N(HI)=7x1020 cm-2

(Pettini et al. 2002)

MS1512-cB58: Outflow Kinematics

stellar systemic velocity

MS1512-cB58: Abundance Pattern

-1

• -elements have 0.4 solar abundance

• Fe-peak elements and N are less abundant

• cB58 is chemically young

(Pettini et al. 2002)

MS1512-cB58: Population Synthesis

• Top: Z=Zsun (dotted line)

• Bottom: Z=0.25Zsun (dashed line)

• Actual data (solid line)

(Leitherer et al. 2001)

Both models have 100 Myr continuous SF, Salpeter IMF, M=1-100Msun

50 GOODS-N Galaxies, z=1.5-2.0

94 z=2-2.5 Galaxies in the GOODS-N Field

Deep in the Desert: 10-20 hr Spectra w/LRIS-B (4-5 A resol’n)

The “Galaxy Proximity Effect ”?Galaxies “clear out” a region in the neutral H within ~700 kpc (co-

moving)?

There is an excess of HI absorption within ~6 Mpc

of galaxies, on average

Average flux in the Lyman alpha

forest at z=3

Adelberger, CS, Shapley, Pettini 2003

Croft et al 2002

feedback at high redshift

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