Quasars Probing Quasars: Quasars Probing Quasars: Shedding (Quasar) Light on Shedding (Quasar) Light on

High Redshift GalaxiesHigh Redshift Galaxies

Joseph F. HennawiUC Berkeley

Ohio StateFebruary 20, 2007

Suspects

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Xavier Prochaska(UCSC)

Scott Burles(MIT)

Juna Kollmeier (Carnegie) & Zheng Zheng (IAS)

OutlineOutline

• Motivation

• Finding close quasar pairs

• IGM Primer

• Quasar-Absorber Clustering

• Fluorescent Ly Emission

Bottom Line: The physical problem of a quasar illuminating an optically thick cloud of HI is very simple compared to other problems in galaxy formation.

MotivationMotivation

A Simple ObservationA Simple Observation

Spectrum from Wallace Sargent

Quasars Evolution for PoetsQuasars Evolution for Poets

nQSO(> L) :

tQSO

tH

Ω4π

⎛⎝⎜

⎞⎠⎟nRelics(> MBH )

Com

ovin

g N

um

ber

Den

sity

L*(

z)/L

*(0)

Dramatic evolution of number density/ luminosity

look back time

Boyle et al. (2001)

Richards

et al. (2006)Tremaine et al. (2002)

z (redshift)

nQSO(> L) :

tQSO

tH

Ω4π

⎛⎝⎜

⎞⎠⎟nHosts

Quasar Evolution for PunditsQuasar Evolution for Pundits

BLAGN Steffen et al. (2003)

unidentified

non-BLAGN

The AGN unified model breaks down at high luminosities.

“Almost all luminous quasars are unobscured . . . ”

Barger et al. (2005)

AGN unified model

106 M

3105 M

105 M Engargiola et al. (2002)

HI in High Redshift Galaxies?HI in High Redshift Galaxies?

Image credit: Fabian Walter

Radial CO and HI profiles for 7 nearby galaxies

(Wong & Blitz 2002).

M33 HI/H/Optical M33 HI/CO

• The HI is much more extended than the stars and molecular gas.

• Until SKA, no way to image HI at high redshift.

• HI is what simulations of galaxy formation might predict (reliably).

The Power of Large SurveysThe Power of Large SurveysApache Point Observatory (APO) • Spectroscopic QSO survey

– 5000 deg2

– 45,000 z < 2.2 ; i < 19.1– 5,000 z > 3; i < 20.2– Precise (u,g,r, i, z) photometry

• Photometric QSO sample– 8000 deg2

– 500,000 z < 3 ; i < 21.0– 20,000 z > 3 ; i < 21.0 – Richards et al. 2004; Hennawi et al. 2006

SDSS 2.5m

ARC 3.5m

Jim Gunn

Follow up QSO pair confirmation

from ARC 3.5m and MMT 6.5m

MMT 6.5m

= 3.7”

2’55”

ExcludedArea

Finding Quasar PairsFinding Quasar Pairs

SDSS quasar @ z =3.13

4.02.0

3.0

2.03.0

3.0

2.04.0

low-zQSOs

Cosmology with Quasar PairsCosmology with Quasar PairsClose Quasar Pair Survey

• Discovered > 100 sub-Mpc pairs (z > 2)

• Factor 25 increase in number known

• Moderate & Echelle Resolution Spectra

• Near-IR Foreground QSO Redshifts

• 45 Keck & Gemni nights. 8 MMT nights

= 13.8”, z = 3.00; Beam =79 kpc/h

Spectra from Keck ESI

Keck Gemini-N

Science• Dark energy at z > 2 from AP test

• Small scale structure of Ly forest

• Thermal history of the Universe

• Topology of metal enrichment from

• Transverse proximity effects

Gemini-S MMT

Collaborators: Jason Prochaska, Crystal Martin, Sara Ellison, George Djorgovski, Scott Burles, Michael Strauss

Ly Forest Correlations

CIV Metal Line Correlations

Nor

mal

ized

Flu

x

IGM PrimerIGM Primer

Quasar Absorption LinesQuasar Absorption Lines

DLA (HST/STIS)

Moller et al. (2003)

LLS

Nobody et al. (200?)

Lyz = 2.96

Lyman Limitz = 2.96

QSO z = 3.0 LLS

Lyz = 2.58

DLA

• Ly Forest– Optically thin diffuse IGM / ~ 1-10; 1014 < NHI < 1017.2

– well studied for R > 1 Mpc/h

• Lyman Limit Systems (LLSs)– Optically thick 912 > 1

– 1017.2 < NHI < 1020.3

– almost totally unexplored

• Damped Ly Systems (DLAs)– NHI > 1020.3 comparable to disks

– sub-L galaxies?

– Dominate HI content of Universe

Self Shielding: A Local ExampleSelf Shielding: A Local Example

Sharp edges of galaxy disks set by ionization equilibrium with the UV background. HI is ‘self-shielded’ from extragalactic UV photons.

Braun & Thilker (2004)M31 (Andromeda) M33 VLA 21cm map

DLA

Ly forest

LLS

What if the MBH = 3107 M black hole at Andromeda’s center started accreting at the Eddington limit? What would M33 look like then?

bump due

to M33

Average HI of Andromeda

Neutral Gas

Isolated QSO

Proximity EffectsProximity Effects

• Proximity Effect Decrease in Ly forest absorption due to large ionizing flux near a quasar

• Transverse Proximity Effect Decrease in absorption in background QSO spectrum due to transverse ionizing flux of a foreground quasar– Geometry of quasar radiation field (obscuration?)

– Quasar lifetime/variability

– Measure distribution of HI in quasar environments

Are there similar effects for optically thick absorbers?

Ionized Gas

Projected QSO Pair

nQSO :

tQSO

tH

Ω4π

⎛⎝⎜

⎞⎠⎟nHosts

Fluorescent LyFluorescent Ly Emission Emission

• In ionization equilibrium ~ 60% of recombinations yield a Ly photon

• Since 1216 > 104 912 , Ly photons must ‘scatter’ out of the cloud

• Photons only escape from tails of velocity distribution where Ly is small

• LLSs ‘reflect’ ~ 60% of UV radiation in a fluorescent double peaked line

Zheng & Miralda-Escude (2002)

912 ~ 1 in self shielding skin

Shielded HI

UV Background

x =δυ /υσ / c

= 0e−(x2 /2)

Only Ly photons in tail can escape

P(v)

v dist of cloud

Imaging Optically Thick AbsorbersImaging Optically Thick Absorbers

Cantalupo et al. (2005)

Column Density Ly Surface Brightness

• Expected surface brightness:

• Still not detected. Even after 60h integrations on 10m telescopes!

or

Sounds pretty hard!

SBLy =3.7 ×10−20 J −22

912

4⎛

⎝⎜⎞

⎠⎟1+ z4

⎛⎝⎜

⎞⎠⎟

−4

ergs cm-2s-1W" μLyα = 30 mag/W"

Help From a Nearby QuasarHelp From a Nearby Quasar

Adelberger et al. (2006)

DLAtrough

2-d Spectrum of Background Quasar

Spatial Along Slit (”)W

avel

engt

h

extended emission

r = 15.7!

Doubled Peaked Resonant Profile?

Background QSO spectrum

Transverse flux = 5700 UVB!

f/g QSO

R = 384 kpc

11 kpc

4 kpc

Why Did Chuck Get So Lucky?Why Did Chuck Get So Lucky?

f/g QSO

R||

b/g QSO

R = 280 kpc/h

DLA must be in this

region to see emission

• Surface brightness consistent with expectation for R|| = 0

• R|| constrained to be very small, otherwise fluorescence would be way too dim.

If we assume emission was detected at (S/N) = 10, then (S/N) > 1 requires:

R|| < R [(S/N) -1]1/2 = 830 kpc/h or dz < 0.004

Since dN/dz(DLAs) = 0.2, then the probability PChuck = 1/1000!

I should spend less time at Keck, and more time in Vegas $$

Chuck Steidel

Perhaps DLAs are strongly clustered around quasars?

Quasar-Absorber Clustering

Quasar-Absorber Clustering

Quasars Probing QuasarsQuasars Probing Quasars

Hennawi, Prochaska, et al. (2007)

Transverse ClusteringTransverse Clustering

• 29 new QSO-LLSs with R < 2 Mpc/h

• High covering factor for R < 100 kpc/h

• For T(r) = (r/rT)-, = 1.6, and NHI > 1019

cm-2, rT = 9 1.7 (2.9 QSO-LBG)

Hennawi, Prochaska et al. (2007); Hennawi & Prochaska (2007)

Chuck’s object

= Keck = Gemini = SDSS

= has absorber = no absorber

En

han

cem

ent

over

UV

Bz

(re

dsh

ift)

= 2.0 = 1.6

QSO-LBG

Proximate DLAs: LOS clusteringProximate DLAs: LOS clustering

• Found 12 PDLAs out of ~ 2000 z < 2.7 quasars

Prochaska, Hennawi, & Herbert-Fort (2007)

dN

dz(< 3000 km/s) =(1.4 ±0.3)

dNdz

• Transverse clustering strength at z = 2.5 predicts that nearly every QSO

should have an absorber with NHI > 1019 cm-2 along the LOS??

• Rapid redshift evolution of QSO clustering compared to paucity of

proximate DLAs implies that photoevaporation has to be occurring.

PhotoevaporationPhotoevaporation

f/g QSO

b/g QSO

R

QSO is to DLA . . . as . . . O-star is to interstellar cloud

Γ =nphotons

nH

= 2.6 ×10−4 S56RMpc-2 n−1

H, -1

Hennawi & Prochaska (2007)

δ =500ΓNH

1020.3cm-2

⎛⎝⎜

⎞⎠⎟

−1

< 1

Otherwise it is photoevaporatedBertoldi (1989), Bertodi & McKee (1989)

Cloud survives provided

r = 17r = 19r = 21

nH = 0.1

Proximity Effects: SummaryProximity Effects: Summary

• There is a LOS proximity effect but not a transverse one.

• Photoevaporation plausible for absorbers near quasars.

• Our measured T(r) gives, PChuck = 1/65.

• Fluorescent emission proves Chuck’s DLA was illuminated.

• Clustering anisotropy suggests transverse systems are not.

• Two possible sources of clustering anisotropy:

– QSO ionizing photons are obscured (beamed?)

– QSOs vary significantly on timescales shorter than crossing time:

tcross ~ 4 105 yr @ = 20” (120 kpc/h).

Current limit: tQSO > 104 yr

Proximity Effects: Open QuestionsProximity Effects: Open Questions

• Can we measure the average opening angle?

– Yes, but must model photoevaporation assuming an

absorber density profile.

– Much easier for optically thin transverse effect (coming

soon).

• Does high transverse covering factor conflict with

obscured fractions (~ 10%) of luminous QSOs?

• Why did Chuck’s DLA survive whereas others are

photoevaporated?

Fluorescent Ly Emission

Fluorescent Ly Emission

Transverse Fluorescence?Transverse Fluorescence?

background QSO spectrum

2-d spectrum

f/g QSO z = 2.29

PSF subtracted 2-d spectrum

(Data-Model)/Noise

Hennawi, Prochaska, & Burles (2007)

b/g QSO z = 3.13 Implied transverse ionizing flux

gUV = 6370 UVB!

Near-IR Quasar RedshiftsNear-IR Quasar Redshifts

Transverse Fluorescence?Transverse Fluorescence?

Background QSO spectrum

2-d spectrum

f/g QSO z = 2.27

PSF subtracted 2-d spectrum

(Data-Model)/Noise

Hennawi, Prochaska, & Burles (2007)

b/g QSO z = 2.35 Implied transverse ionizing flux

gUV = 7870 UVB!

metals at this z

LyLy Emission from DLAs Emission from DLAs

Could the proximate DLA emission be fluorescence excited by the quasar ionizing flux?

Moller et al. (2004)

HST STIS Image

2-d Spectrum

QSO zQSO zDLAf Ly

(10-17 erg s-1 cm-2)

L Ly

(1042 erg s-1)

PKS 0458-02 2.286 2.0395 5.4 0.17

PC0953+4749 4.457 3.407 0.7 0.77

Q 2206-1958 2.559 1.9205 26 14

DMS 2247-0209 4.36 4.097 0.5 0.9

PHL 1222 1.922 1.9342 90 25

B 0405-331 2.57 2.570 ??? ???

PSK 0528-250 2.77 2.8115 7.4 0.49

SDSSJ 1240+1455 3.107 3.1078 43 39

Q2059-360 3.10 3.0830 20 18

Intervening DLAs

Proximate DLAs

Fluorescent PhasesFluorescent Phases

R

f/g QSOTransverse

b/g QSO

Absorber

Full Moon? Absorber

f/g QSO

Absorber

Proximate b/g QSO

A Fluorescing PDLA?A Fluorescing PDLA?

• Ly brighter than 95% of LBGs --- unlikely to be star formation.

• Detection of N(N+4) > 1014.4 cm-2 consistent with hard QSO spectrum and requires R|| < 700 kpc.

• Large fLy = 4.310-16 erg s-1 cm-2 suggests R|| ~ 300 kpc.

• If emission is Ly from QSO halo, then we can image DLA in silhouette.

Hennawi, Kollmeier, Prochaska, & Zheng (2007)

R||

DLA

b/g QSO

New Probes of HI in High-z GalaxiesNew Probes of HI in High-z Galaxies

• These observables are predictable given a model for HI distribution in high-z galaxies.

• The physics of self-shielding and resonant line radiative transfer are straightforward compared to other problems in galaxy formation.

Hennawi, Kollmeier, Prochaska, & Zheng (2007)

Statistics of PDLAs Fluorescent Ly Emission

Photo-evaporation of DLAs

Ly Emissivity Map Aperture Spectra

Hennawi, Prochaska,

& Herbert-Fort (2007)

Column distribution near QSOs

SummarySummary

• With projected QSO pairs, QSO environments can be studied down to ~ 20 kpc where ionizing fluxes are as large as 104 times the UVB.

• Clustering pattern of absorbers around QSOs is highly anisotropic.

• Rapid redshift evolution of QSO clustering compared to paucity of proximate DLAs implies that photoevaporation has to be occuring.

• Physical arguments indicate that DLAs within 1 Mpc of a luminous quasar can be photoevaporated.

• QSO-LLS pairs provide new laboratories to study Ly fluorescence.

• Null detections of fluorescence and clustering anisotropy suggest that quasar emission is either anisotropic or variable on timescales < 105 yr.

• Photoevaporation and fluorescent emission provide new physical constraints on the distribution of HI in high-z proto-galaxies. The input physics is relatively simple and it can be easily modeled.