quasars probing quasars: shedding (quasar) light on high redshift galaxies joseph f. hennawi uc...
Post on 19-Dec-2015
222 views
TRANSCRIPT
![Page 1: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/1.jpg)
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
![Page 2: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/2.jpg)
Suspects
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Xavier Prochaska(UCSC)
Scott Burles(MIT)
Juna Kollmeier (Carnegie) & Zheng Zheng (IAS)
![Page 3: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/3.jpg)
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.
![Page 4: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/4.jpg)
MotivationMotivation
![Page 5: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/5.jpg)
A Simple ObservationA Simple Observation
Spectrum from Wallace Sargent
![Page 6: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/6.jpg)
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
![Page 7: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/7.jpg)
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
![Page 8: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/8.jpg)
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).
![Page 9: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/9.jpg)
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
![Page 10: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/10.jpg)
= 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
![Page 11: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/11.jpg)
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
![Page 12: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/12.jpg)
IGM PrimerIGM Primer
![Page 13: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/13.jpg)
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
![Page 14: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/14.jpg)
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
![Page 15: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/15.jpg)
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
![Page 16: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/16.jpg)
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
![Page 17: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/17.jpg)
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"
![Page 18: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/18.jpg)
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
![Page 19: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/19.jpg)
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?
![Page 20: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/20.jpg)
Quasar-Absorber Clustering
Quasar-Absorber Clustering
![Page 21: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/21.jpg)
Quasars Probing QuasarsQuasars Probing Quasars
Hennawi, Prochaska, et al. (2007)
![Page 22: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/22.jpg)
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
![Page 23: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/23.jpg)
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.
![Page 24: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/24.jpg)
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
![Page 25: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/25.jpg)
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
![Page 26: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/26.jpg)
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?
![Page 27: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/27.jpg)
Fluorescent Ly Emission
Fluorescent Ly Emission
![Page 28: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/28.jpg)
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!
![Page 29: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/29.jpg)
Near-IR Quasar RedshiftsNear-IR Quasar Redshifts
![Page 30: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/30.jpg)
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
![Page 31: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/31.jpg)
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
![Page 32: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/32.jpg)
Fluorescent PhasesFluorescent Phases
R
f/g QSOTransverse
b/g QSO
Absorber
Full Moon? Absorber
f/g QSO
Absorber
Proximate b/g QSO
![Page 33: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/33.jpg)
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
![Page 34: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/34.jpg)
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
![Page 35: Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007](https://reader036.vdocuments.us/reader036/viewer/2022062516/56649d385503460f94a11b8b/html5/thumbnails/35.jpg)
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.