Joseph F. Hennawi UC Berkeley &
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Transcript of Joseph F. Hennawi UC Berkeley &
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Joseph F. HennawiUC Berkeley
&
OSUOctober 3, 2007
Xavier Prochaska(UCSC)
Quasars Probing QuasarsQuasars Probing Quasars
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A Simple Observation
Spectrum from Wallace Sargent
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The Basic Picture
HI cloud
Line-of-SightQSO
Transverseb/g QSO
f/g QSOR||
R
HI cloud
• Ly absorption can probe 8 decades in NHI (Ly is large!).
• Neighboring sightline provides a another view of the QSO. • Redshift space distortions from kT motions (~ 20 km/s )
smooth with Gaussian of Rprop ~ 60 kpc = 10” @ z = 2.
• Need projected QSO pairs to study small scales!
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What Can Proximity Effects Teach Us?
• How is HI distributed around quasars?• What is the quasar duty cycle tQSO/tH ?• What is the obscured fraction (1- Ω/4)?• Can we constrain episodic QSO variability, tburst?• Directly observe impact of AGN feedback on the IGM?
nQSO (> L) :
tQSOtH
Ω4
⎛⎝⎜
⎞⎠⎟nHot/Relic(> ?) ;
Ω4π
=nQSO
nQSO + nobscured
Physics of IGM well understood no sub-grid physics or semi-analytical recipes!
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Mining 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 confirmationfrom ARC 3.5m and MMT 6.5m
MMT 6.5m
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= 3.7”
2’ 55”
ExcludedArea
Finding Quasar Pairs
SDSS QSO @ z =3.13
4.02.0
3.0
2.03.0
3.0
2.04.0
low-zQSOs
f/g QSO z = 2.29
b/g QSO z = 3.13
Keck LRIS spectra l (Å)
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Cosmology 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• About 50 Keck & Gemni nights.
= 13.8”, z = 3.00; Beam =79 kpc/hSpectra 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
Collaborators: Jason Prochaska, Crystal Martin, Sara Ellison, George Djorgovski, Scott Burles
Ly Forest Correlations
CIV Metal Line Correlations
Nor
mal
ized
Flu
x
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Quasar 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 t912 > 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
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Self 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
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Neutral Gas
Isolated QSO
Proximity 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
Ω4
⎛⎝⎜
⎞⎠⎟nHot
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Transverse Optically Thick
Hennawi, Prochaska, et al. (2007)
zbg = 3.13; zfg= 2.29; R = 22 kpc/h; logNHI = 20.5
zbg = 2.07; zfg= 1.98; R = 139 kpc/h; logNHI = 19.0
zbg = 2.21; zfg= 2.18; R = 61 kpc/h; logNHI = 18.5
zbg = 2.53; zfg= 2.43; R = 78 kpc/h; logNHI = 19.7
zbg = 2.35; zfg= 2.28; R = 37 kpc/h; logNHI = 18.9
zbg = 2.17; zfg= 2.11; R = 97 kpc/h; logNHI = 20.3
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Transverse Optically Thick ClusteringHennawi, Prochaska et al. (2007);
Hennawi & Prochaska (2007)
= Keck = Gemini = SDSS
= has absorber = no absorber
Enh
ance
men
t ove
r U
VB
z (
reds
hift
)
= 2.0 = 1.6
QSO-LBG
• 29 new QSO-LLSs with R < 2 Mpc/h
• High covering factor for R < 100 kpc/h
• For T(r) = (r/rT)-, = 1.6, log NHI > 19
rT = 9 1.7 Mpc/h (3 QSO-LBG)
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Line-of-Sight Clustering
Prochaska, Hennawi, & Herbert-Fort (2007)
• Factor 5-10 fewer PDLAs then expected from transverse clustering. • Transverse clustering strength at z = 2.5 predicts that ~ 90% of QSO’s 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.
Transverse prediction
1 + c |
|(∆v)
z
Line-of-Sight Clustering Strength
Extrapolation of trans. predictions
Line-of-sight measurements
Proximate DLA DLA within v < 3000 km/s
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Photoevaporation
f/g QSO
b/g QSO
R
QSO is to DLA . . . as . . . O-star is to interstellar cloud
Γ =nphotons
nH
= 2.6 ×10−4S56RMpc-2 n−1
H, -1
Hennawi & Prochaska (2007a)
δ =trect IF
= 500ΓNH
1020.3cm-2⎛⎝⎜
⎞⎠⎟
−1
< 1
Otherwise it is photoevaporatedBertoldi (1989), Bertodi & McKee (1989)
Cloud survives provided
r = 17r = 19r = 21
nH = 0.1
log NHI = 20.3
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Emission AnisotropyObscuration/Beaming
f/g QSO
b/g QSO
Absorber
R
Ω > 104 yr
• Episodic Variability QSO’s vary significantly on timescale t < tcross ~ 4 105 yr @ = 20” (120 kpc/h).
Current best limit is tburst > 104 yr.
Episodic Variability
f/g QSO
b/g QSO
Absorber
We observe light emitted at time t = t0
Ionization state of gas depends on QSO at time t = t0 - R/c R
t = t0
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• Optically Thick LLSs and DLAs (today’s talk)– Nature of absorbers near QSO’s is unclear.
• Gas entrained from AGN driven outflow? (AGN feedback!)
• Absorption from nearby dwarf galaxies?
– To measure tQSO/tH or (Ω/4) we need to model absorbers and do radiative transfer (hard).
• Optically Thin Ly Forest (in progess)– Best for constraining tQSO/tH and (Ω/4).
– Why? Because we can predict the Ly forest fluctuations ab initio from N-body simulations (easy).
Proximity Effects: Thick and Thin
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Optically Thin (Sneak Preview)Hennawi, et al. (2007), in prep
= Gemini
= accurate z = no accurate z
Enh
ance
men
t ove
r U
VB
z (
reds
hift
)
Sample• 1.6 < z < 4.5; 20 kpc < R < 10 Mpc
• 59 pairs with gUV > 100.
• 30 accurate near-IR redshifts.
l (m
)
, , = Keck , = SDSS
gUV ≡1+FQSOFUV B
; ′tLyα = τ Lyα gUV
z = 2.4360z = 44 km/s
Gemini NIRI K-band spectrum
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Transverse Proximity Effect?
z = 3.8135z = 44 km/s
zbg = 4.11, zfg= 3.81
= 34”, R = 175 kpc/h
tcross = 5.7107 yr
gUV = 626!
with f/g QSO
without f/g QSO
RealReal
SimulatedSimulated
Hennawi et al. 2007, in prep.
Gemini NIRI K-band spectrumSpectrum from Keck ESI
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Summary• With projected pairs, QSO environments can be probed down
to ~ 20 kpc where ionizing flux is ~ 104 times the UVB. • Clustering of optically thick absorbers around QSOs is highly
anisotropic. • Paucity of PDLAs implies photoevaporation has to occur. • Physical arguments indicate DLAs < 1 Mpc from a QSO can
be photoevaporated. • There is a LOS optically thick proximity effect but no
transverse one.• Either QSOs emit anisotropically or are variable on
timescales < 106 yr.• The optically thin proximity effect will distinguish between
these two possibility and yield new quantitative constraints.