quasars probing quasars joseph f. hennawi berkeley hubble symposium april 20, 2006 z = 2.53 z = 2.44...
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Quasars Probing QuasarsQuasars Probing Quasars
Joseph F. HennawiBerkeley
Hubble SymposiumApril 20, 2006
z = 2.53
z = 2.44
f/g QSO
b/g QSO
R
Suspects
Michael Strauss(Princeton)
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Jason Prochaska(UCSC)
Scott Burles(MIT)
OutlineOutline
• Primer on quasar absorption lines
• Proximity effects
• Fluorescent Ly Emission
• Anisotropic clustering of absorbers around
quasars
• Shedding light on DLAs
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
Cosmology with Quasar PairsCosmology with Quasar PairsClose Quasar Pair Survey
• Discovered ~ 100 sub-Mpc pairs (z > 2)
• Factor 20 increase in number known
• ~ 30 systems with beam < 100 kpc/h
= 5.4”, z = 2.05; Beam =86-99 kpc/h
Spectrum from Keck LRIS-B
Keck Gemini-N MMT
Gemini N-S
Science Goals• Small scale structure of Ly forest
• Transverse proximity effects
• Constrain dark energy from AP test
• Moderate Resolution Spectra
• Near-IR Foreground QSO Redshifts
Fluorescent EmissionFluorescent 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 (2005)
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
egσ cm -2σ-1W" mLyα = 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
5700 UV background!
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!
Perhaps DLAs are strongly clustered around quasars?
I should spend less time at Keck, and more time in Vegas $$
Chuck Steidel
Absorbers Near QuasarsAbsorbers Near Quasars
z = 2.53
z = 2.44
z = 2.17 z = 2.07
z = 1.98z = 2.11
= 16”, R= 97 kpc/h, gUV = 365 = 23”, R= 139 kpc/h, gUV = 420
LLS: NHI = 1019 cm-2
Hennawi, Prochaska, et al. (2006)
DLA: NHI = 1020.3 cm-2LLS: NHI = 1019.7 cm-2
= 13”, R= 78 kpc/h, gUV = 630
Absorption probability for LOS as predicted by transverse clustering
DLAs from
Russell et al. (2006)
No clustering
Anisotropic ClusteringAnisotropic Clustering
• 29 new QSO-LLSs with R < 2 Mpc/h
• High covering factor for R < 100 kpc/h
• Assuming T(r) = (r/rT)-g and g = 1.6, rT
= 9 1.7 (2.9 QSO-LBG)
Transverse clustering predicts every QSO
should have an absorber along the LOS
Hennawi, Prochaska et al. (2006); Hennawi & Prochaska (2006a)
Chuck’s object
= Keck = Gemini = SDSS
= has absorber = no absorber
En
han
cem
ent
over
UV
Bz
(re
dsh
ift)
Proximity Effects: Open QuestionsProximity Effects: Open Questions• There is a LOS proximity effect but not a transverse one.
• Measured T(r) gives, PChuck = 1/60.
• Fluorescent emission proves Chuck’s DLA was illuminated.
• Clustering anisotropy suggests most systems may not be.
• 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 at = 20” (120 kpc/h). Current best limit: tQSO > 104
• Can we measure the average opening angle?
– Yes, but it requires a model for absorbers and QSO-HI clustering.
– Much easier for optically thin transverse effect (coming soon).
• Does high covering factor conflict with obscured fractions (~ 30%)
of luminous QSOs?
• Where are the metals from evaporated DLAs/LLSs near QSOs?
Shedding Light on DLAsShedding Light on DLAs
f/g QSO
b/g QSO
R = 280 kpc/h
gUV = 5700
QSO is to DLA . . . as . . . O-star is to interstellar cloud
‘Typical’ numbers for DLA: Γ =nphotons
nH
= 3 ×10−3 S56
RMpc2
nH
10-2
⎛⎝⎜
⎞⎠⎟
−1
= 2.2
δ =500nH
10−2
⎛⎝⎜
⎞⎠⎟
−1NHI = 1020.3 cm-2 and r ~ 5 kpc
nH ~ 0.01 cm-3
Hennawi & Prochaska (2006a)
ionization parameter
Survival requires nH > 9 cm-3 r < 11 pc. But Chuck’s
fluorescence was resolved in 0.5” seeing r ~ 4 kpc? Two phase medium? Is a disk shielding the galactic halo?
δ =0.29Γ
10−3
⎛⎝⎜
⎞⎠⎟
NHI
1020.3cm-2
⎛⎝⎜
⎞⎠⎟
−1
< 1
Otherwise it is photoevaporatedBertoldi (1989), Bertoldi & Mckee (1989)
Cloud survives provided
Got Fluorescence?Got Fluorescence?
= 6.2”, R= 37 kpc/h
LLS: NHI = 1018.85 cm-23.5 hour integration on Gemini
mLyα ~ 19.5 mag/W"
• gUV = 7900 UVB
expect
(Chuck’s gUV = 5700)
• Two other similar systems show no fluorescence
• ‘Odd’ HI profiles? Unresolved emission?
background QSO spectrum
2-d spectrum
b/g QSO
f/g QSO
PSF subtracted 2-d spectrum
Hennawi & Prochaska (2006b)
Summary: Quasars Probing QuasarsSummary: Quasars Probing Quasars
• QSO-absorber pairs probe anisotropy of luminous QSO
emission at z > 2.
• With fluorescents emission, LLSs act as mirrors giving us
another view of high redshift QSOs.
• New measure of the clustering of faint galaxies around quasars.
• New laboratories to study fluorescent emission. LLSs
illuminated by quasars are as bright as
• Detection of fluorescence constrains quasar lifetime, tQSO
> tcross , for individual QSOs!
• New opportunities to study the distribution of HI in high-z
proto-galaxies subject to extreme UV radiation.
mLyα : 19.5 mag/W"
dN
dz=
dNdz
1+ c(R⊥ ,z)[ ]
Quantifying Absorber Clustering Quantifying Absorber Clustering
• dN/dz only constrains product of number density and cross section.
• Size does not matter for transverse. It does matter for line of sight.
• Only rare close pairs probe small scales for transverse.
• Every isolated line of sight probes small scales.
Far from a QSO
R
Transverse Line of Sight
isolated QSO
dN
dz=nA
dDdz
dN
dz=
dNdz
1+ c(v)[ ]
f/g QSO
Cosmic Average
z r c =1
Vξ (r)dV∫
b/g QSO
z z
cutoff
Close Pairs and the LyClose Pairs and the Ly Forest Forest
Neutral Gas
FWHM
Perfect20 km/s40 km/s80 km/s
160 km/s
1 pair at S/N=20Ability of single pair to distinguish WDE = 0.7 from WDE = 0.8 (courtesy of Pat McDonald)
Goal: Measure transverse Ly correlations of close pairs with z > 2
quasar
– Probe WDE at z ~ 2 with the Alcock - Paczynski test
pair
– Measure ‘Jeans Mass’ of Ly clouds
thermal history of IGM
Science:– Extend power spectrum measurements to small scales
Small Scale Power at z = 2Small Scale Power at z = 2 = 5.4” z = 2.05, 2.09 Beam =86-99 kpc/h (comoving)
Small Scale Power at z = 3Small Scale Power at z = 3 = 13.8” z = 3.0 Beam =274-306 kpc/h (comoving)
Common Absorbers
Tomography with Quasar GroupsTomography with Quasar Groups
8’
5’
z = 2.08 z = 1.8
z = 2.17 z = 2.39
z = 2.6
Keck LRIS mask