Download Evolution of the Highest Redshift Quasars

The Most Distant Quasars
Xiaohui Fan
University of Arizona
June 7, 2010
Collaborators: Brandt, Carilli, de Rosa, Jiang, Kurk,
Richards, Schneider, Shen, Strauss, Vestergaard,
Walter, Wang
Background: 46,420 Quasars from the SDSS Data Release Three
Quasar of the day
• Last night’s astro-ph: Willott et al. new highestredshift quasar at z=6.44
Quest to the Highest Redshift
30 at z>6
60 at z>5.5
>100 at z>5
Key Questions
• When did the first supermassive BH form?
– Measurement of quasar luminosity function and BH
mass at z>6
• When did the first quasar form?
– (lack of ?) Evolution of spectral energy distribution
• Co-evolution of the earliest BHs and galaxies
– Does M-σ relation exist at z>6?
Formation of z~6 quasars
from hierarchical mergers
Li et al. 2007
Theorists Tell us
• These luminous z~6 quasars:
– The most massive system in early
Universe
– Living in the densest environment
– BH accreting at Eddington
– Host galaxies have ULIRG properties
with maximum starburst
Li et al. 2007
Quasar Evolution at z~6
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•
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Strong density evolution
– Density declines by a factor of ~40
from between z~2.5 and z~6
Black hole mass measurements
– MBH~109-10 Msun
– Mhalo ~ 1012-13 Msun
– rare, 5-6 sigma peaks at z~6 (density of
1 per Gpc3)
Luminosity function at z~6
– Bright end slope steep
– LF breaks at M~-25
• Not likely significant contributor
to reionization budget
• bad news for deep quasar surveys
Fan et al. 2006
Low-z
z~6
Willott et al. 2010
Eddington Ratios in z~6 Quasars
z~6 quasars
• Quasar BH mass measured
from near-IR spectroscopy in
CIV and MgII regions
• On average: at or close to
Eddington accretion
See De Rosa poster
Are there luminous quasars at z>>7
• Black Holes do not grow arbitrarily fast
– Accretion onto BHs dicitated by Eddington Limit
– E-folding time of maximum supermassive BH growth: 40 Myr
– At z=7: age of the universe: 800 Myr = maximum 20 e-folding
• Billion solar mass BH at z>7
• Non-stop, maximum accretion from 100 solar mass BHs at
z=15 (collapse of first stars in the Universe)
• Theoretically difficult for formation of z>7 billion solar
mass BHs by Eddington-limited accretion from stellar seeds
• What if we find them:
– Direct collapse of “intermediate” mass BHs?
– More efficient accretion model “super-Eddington”?
non-evolution of quasar (black hole) emission
z~6 composite
Low-z composite
Ly a
NV
Ly a forest
OI
SiIV
XF et al. 2010
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•
•
Jiang, XF et al. 2008
Rapid chemical enrichment in quasar vicinity
Quasar env has supersolar metallicity : no metallicity evolution
High-z quasars are old, not yet first quasars, and live in metally enriched env
similar to centers of massive galaxies
When did the first quasar form?
Dust: emitting
in infrared
radiation from X-ray to radio as a result of black hole
accretion and growth
Hot dust in z~6 Quasars
• Lack of evolution in UV,
emission line and X-ray  disk
and emission line regions form in
very short time scale
• But how about dust? Timescale
problem: running out of time for
AGB dust
• Spitzer observations of z~6
quasars: probing hot dust in dust
torus (T~1000K)
• Three unusual SEDs among ~30
objects observed.
dust
Jiang, XF et al. 2006, 2010
No hot dust??
Disappearance of Dust Torus at z~6?
typical
J0005
3.5m
4.8m
5.6m 8.0m 16m
24m
• quasars with no hot dust
• Spitzer SEDs consistent
with disk continuum only
• No similar objects known
at low-z
• no enough time to form
hot dust tori? Or formed in
metal-free environment?
Jiang, XF et al. 2010
Epoch of first quasars?
Dust/Bolometric
Dust-free quasars:
Dust/Bolometric
• Only at the highest redshift
• With the smallest BH mass
• First generation supermassive
BHs from metal-free environment?
• How are they related to PopIII?
BH mass
Jiang, XF et al. 2010
Probing quasar host galaxies at high-z
[OIII]
Direct imaging: hard!
Radio/sub-mm!
CO
Star Formation in z~6 Quasars
• 30% of z~6 quasars
detected at 1mJy level
in 1-mm ->
– LFIR~ 1013Lsun
– T~50K
– SFR~1000 Msunyr-1 (if
dust heated by SB)
• New CO observations
– eight quasars detected
in CO
– Probing ISM properties
and host galaxy masses
Wang et al. 2008, 2009
Maximum starburst in z=6.4 quasar ?
•
Spatially resolved CO and [CII] emissions:
– Size: ~1.5 kpc from [CII] (0.3”)
– Continuum has >50% extended component: SB heating?
– Star formation rate of: ~1000 Msunyr-1kpc-2
• Eddington limited maximum star formation rate
(Thompson et al.)?
• Gas supply exhaused over a few tdyn
– Similar SF intensity to Arp 200 but 100 times larger!
• Dynamical mass:
1kpc
Walter et al. 2004
– CO/CII line width ~300km/s
– Dynamical mass ~1011Msun?
– BH formed earlier than completion of galaxy assembly?
–
Walter et al. 2009
Do z~6 Quasars Live in the
Densest Environments?
• High-redshift quasars are strongly clustered
Shen et al. 2007
• But efforts to look for overdensity around z~6
quasars have mostly produced non-results (Willott
et al., Kim et al., Kurk et al., Zheng et al.)
Do z~6 Quasars Live in the
Densest Environments?
• Non-detection of significant overdensity around
z~6 quasars:
– Quasars suppress dwarf galaxy formation?
– Quasar hosts are not massive?
– Needs deeper and wider surveys
Overzier et al. 2008
Conclusions and Questions
• Rapid evolution of quasar density at z~6
– Are we closing in to the epoch of the earliest SBH formation?
• First hot dust at z~6
– Are we closing in to the epoch of first AGN structure?
• Luminous quasars seem to live in modest environments
– Narrow CO line width  small host mass
– No significant overdensity of galaxies
– How closely tied are the earliest SBHs and galaxies? Or are we
just picking up early starters in term of BH accretion in the
most luminous quasars?
• Important changes at z~6: needs to push for
higher redshift and lower luminosities
Quest to the Highest Redshift
Quest to the Highest Redshift
090423
080913
050904
000131
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970228
Probing Reionization History
WMAP