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Shedding (Quasar) Light on High Redshift Galaxies
Shedding (Quasar) Light on High Redshift Galaxies
Joseph F. HennawiUC Berkeley
Hubble Fellowship SymposiumApril 2, 2007
Suspects
Jason X. Prochaska(UCSC)
Juna Kollmeier (Carnegie) & Zheng Zheng (IAS)
Hubble Fellow Class of 2001
Hubble Fellow Classes of 2006 and 2004
OutlineOutline
• Finding close projected quasar pairs
• IGM Physics Primer
• Fluorescent Ly Emission
Bottom Line: The physical problem of a quasar illuminating a high redshift galaxy is very simple compared to other problems in galaxy formation.
The AGN Unified ModelThe AGN Unified Model
BLAGN Steffen et al. (2003)
unidentified
non-BLAGN
The AGN unified model breaks down at high luminosities.
“Nearly all (~ 90%) luminous quasars are unobscured . . . ”
Barger et al. (2005)
AGN unified model
BLAGN
obscured non-BLAGN
Ω=4πnBLAGN
nhard X-ray
Mining Large SurveysMining 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 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 (Å)
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
• 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
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
Fluorescent Ly EmissionFluorescent Ly Emission
• In ionization equilibrium ~ 60% of recombinations yield a Ly photon
• Since 1216 > 104 912 , Ly photons must ‘diffuse’ out of the cloud
• Photons only escape from tails of velocity distribution where Ly is small
• LLSs ‘reflect’ ~ 60% of UV continuum in a fluorescent double peaked line
Zheng & Miralda-Escude (2002)
In self shielding skin
912 ~ 1; Ly ~ 104
Self-Shielded HI
UV Background
x =ν −ν0
νD
= 0e−(x2 /2)
Only Ly photons in tail can escape
P(x)
Escape Probability
Resonant Line Emission Profile
x
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
Transverse Fluorescence?Transverse Fluorescence?
Implied transverse flux
gUV = 6370 UVB!
fLy< 410-18 erg/cm2/s
Could detect signal to
R|| < 7.5 R = 170 kpc/hbackground QSO spectrum
2-d spectrum
f/g QSO z = 2.29
PSF subtracted 2-d spectrum
(Data-Model)/Noise
Hennawi & Prochaska (2007)
b/g QSO z = 3.13
2 hours Keck LRIS-B
f/g QSO
R||
b/g QSO
R = 22 kpc/h
Probability of null detection:
P(Ω=4) = 9%
P(Ω=2) = 77%
Near-IR Quasar RedshiftsNear-IR Quasar Redshifts
Transverse Fluorescence?Transverse Fluorescence?
metals at this zBackground QSO spectrum
2-d spectrum
f/g QSO z = 2.27
PSF subtracted 2-d spectrum
(Data-Model)/Noise
Hennawi & Prochaska (2007)
b/g QSO z = 2.35
6 hours Gemini GMOS
Implied ionizing flux
gUV = 7870 UVB!
fLy< 510-18 erg/cm2/s
Could detect signal to
R|| < 7.8 R = 295 kpc/h
f/g QSO
R||
b/g QSO
R = 38 kpc/h
near-IR f/g z
Probability of null detection:
P(Ω=4) = 5%
P(Ω=2) = 76%
PunchlinePunchline
• With projected QSO pairs, QSO environments can be studied down to ~ 20 kpc where ionizing fluxes are as large as 104 times the UVB.
• QSO-absorber pairs provide new laboratories to study Ly fluorescent emission without at 30m telescope.
R
f/g QSO
b/g QSO
Absorber
Aperture SpectraLy Emissivity
Kollmeier et al. (2007); Hennawi, Kollmeier, Prochaska, & Zheng (2007)
• The physics of self-shielding and Ly resonant line radiative transfer are very simple compared to other problems in galaxy formation.