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Lecture 3: The Highest Redshift Quasars: Early Black Hole Evolution and the End of Reionization. Xiaohui Fan AGN Summer School, USTC May 25, 2007. Background: 46,420 Quasars from the SDSS Data Release Three. Quest to the Highest Redshift Quasars. IR survey. SDSS. CCD. Radio.

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lecture 3 the highest redshift quasars early black hole evolution and the end of reionization

Lecture 3: The Highest Redshift Quasars:Early Black Hole Evolution and the End of Reionization

Xiaohui Fan

AGN Summer School, USTC

May 25, 2007

Background: 46,420 Quasars from the SDSS Data Release Three

the highest redshift quasars today
z>4: >1000 known

z>6: 15

SDSS i-dropout Survey:

Completed in June 2006:

7700 deg2, zAB < 20

27 luminous quasars at 5.7<z<6.4

Other on-going z~6 quasar surveys:

AGES (Cool et al.): Spitzerselected, one quasar at z=5.8

FIRST-Bootes (Becker et al.): radio selected, one quasar at z=6.1

QUEST, CFHT: i-dropout surveys similar to SDSS

Future IR-based survey: UKIDSS, VISTA, allows detection up to z~8-9.

SDSS2 : faint quasars in the deep SDSS stripe (Jiang, XF et al.), ~10 - 30 additional z~6 quasars in next three years (six z~6 quasar in pilot obs)

The Highest Redshift Quasars Today
what have changed in quasar properties since z 6
What have changed in quasar properties since z~6?
  • Luminous, “normal” looking quasars existed at z>6, half Gyr after the first star-formation
    • Timescale for formation of the first billion-Msun BH?
    • Timescale for the establishment of AGN structure: do quasar spectra at z~6 really look the same as at z~0?
    • Timescale for the establishment of M-sigma relation?
outline
Outline
  • Quasar luminosity function and BH mass function
    • Evolution in accretion properties?
  • Quasar SEDs at high-redshift
    • First signs of cosmic evolution?
  • Star-formation and dust in quasar host galaxies
    • Evolution of M-sigma relation?
  • Probing Reionization with high-redshift quasars
  • Summary
slide8

46,420 Quasars from the SDSS Data Release Three

5

Ly forest

3

Ly

2

CIV

redshift

CIII

MgII

FeII

1

FeII

OIII

H

0

wavelength

4000 A

9000 A

quasar density at z 6
From SDSS i-dropout survey

Density declines by a factor of ~40 from between z~2.5 and z~6

Cosmological implication

MBH~109-10 Msun

Mhalo ~ 1012-13 Msun

rare, 5-6 sigma peaks at z~6 (density of 1 per Gpc3)

Assembly of supermassive BHs?

Assembly of dark matter halo?

Quasar Density at z~6

Fan et al. 2006

simulating z 6 quasars
Simulating z~6 Quasars
  • The largest halo in Millennium simulation (500 Mpc cube) at z=6.2
    • Virial mass 5x1012 M_sun
    • Stellar mass 5x1010 M_sun
    • Resembles properties of SDSS quasars
    • Such massive halos existed at z~6, but..

Dark matter

galaxy

z=6.2

z=0

Springel et al. 2005

constraining early bh growth
Constraining Early BH Growth
  • Timescale
    • At z~6, the Universe is about 20 tedd old (radiative efficiency of 0.1)
    • Enough time to grow 109 Msun BH?
  • Semi-analytic model of early BH growth (Volonteri & Rees 2006)
    • Traces halo merger and BH accretion/merger history
    • Negative feedbacks slowing down BH growth:
      • Rocket effect from BH mergers (BH kicked out from shallow potential wells)
      • Spin up of BHs
        • Increased radiative efficiency and Eddington timescale
    • Extremely difficult for standard thin-disk, Eddington-limited growth from stellar seed BHs… but still allowed
  • Predictions on BH properties
    • Only BHs with ideal growth conditions (negative feedback not important) can grow to billion Msun at z~6
    • Low BH fraction in halos at the high luminosity (mass) end
      • Steep quasar luminosity function?
quasar luminosity function at z 6
Quasar Luminosity Function at z~6
  • Based on:
    • SDSS Wide: 7700 deg2, 17 quasars, zAB <20
    • SDSS Deep: ~150 deg2, 6 quasars, 20<zAB<21
    • AGES: 1 quasar in 5 deg2 at zAB<21.5
  • Steeppening of LF:
    • L<-3.1
    • Comparing to L-2.4 at z~4
  • At z~7-8, quasar growth will severely limited by timescale: intermediate mass seeds and/or super-Eddington accretions may be needed

Jiang, XF et al. in prep

outline13
Outline
  • Quasar luminosity function and BH mass function
    • Evolution in accretion properties?
  • Quasar SEDs at high-redshift
    • First signs of cosmic evolution?
  • Star-formation and dust in quasar host galaxies
    • Evolution of M-sigma relation?
  • Probing Reionization with high-redshift quasars
  • Summary
slide14

The Lack of Evolution in Quasar Emission Line Properties

Ly a

NV

Ly a forest

OI

SiIV

Fan et al.2004

  • Rapid chemical enrichment in quasar vicinity
  • Quasar env has supersolar metallicity : no metallicity evolution
  • Does this lack of evolution in rest-frame UV also apply to other wavelength?
high metallicity at high z
High Metallicity at high-z
  • Strong metal emission  consistent with supersolar metallicity
  • NV emission  multiple generation of star formation from enriched pops
  • Fe II emission  type II SNe… some could be Pop III?

Barth et al. 2003

Nagao et al. 2006

quasar metallicity at z 6
Quasar Metallicity at z~6

near-IR spectroscopy:

Gemini + Keck

Jiang, XF et al. 2007

early enrichment of quasars
Metallicity in BLR of z~6 quasars: 1 -- 10 solar

Nuclear synthesis model shows:

Normal IMF is sufficient (given high SFR)

Type Ia is not critical in Fe production

Mostly Pop III under-produce N/C

“normal” stars existed at very high-z in quasar environment.

Early enrichment of quasars

Top-heavy IMF

PopIII

Normal IMF

Venkatesan et al. 2004

quasar spectral energy distribution
Quasar spectral energy distribution

BLR

 Dust torus

hot dust

disk

Spitzer

  • Cool Dust in

host galaxy

evolution of quasar seds x ray to radio
Evolution of Quasar SEDs: X-ray to radio
  • To the first order, average SEDs of z~6 quasar consistent with low-z template
  • However, detailed analysis might be indicating first signs of SED evolution:
    • Dust properties (Spitzer and extinction)
    • Fraction of radio-loud quasars

Jiang, XF et al. 2006a

hot dust in z 6 quasars
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)
  • Two unusual SEDs among 13 objects observed.

dust

No hot dust??

Jiang, XF et al. 2006a

where did the hot dust go
Where did the hot dust go?

typical

J0005

luminosity

3.5m

4.8m

5.6m

8.0m

24m

  • J0005 (z=5.85):
    • SED consistent with disk continuum only
    • No similar objects known at low-z
    • formation of the first dust ? Larger sample…
    • ~80 objects in Spitzer Cycle 4

Host dust contribution

Jiang, XF 2006a

evolution of radio loudness
Evolution of Radio-loudness
  • Match all SDSS quasars to FIRST and NVSS catalog:
    • For the whole flux-limited sample, radio-loud fraction doesn’t strongly depend on luminosity or redshift
    • However, this seems to be an artifact of marginal distribution…

Jiang, XF et al. 2006b

radio loud fraction is a strong function of luminosity and redshift
Radio-loud fraction is a strong function of luminosity and redshift

log(radio-loud fraction)

  • Luminosity dependence:
    • RLF ~ L0.5
    • At z~1: RLF changes from 17% (M=-27) to 2% (M=-22)
  • Redshift dependence:
    • RLF ~ (1+z)-1.7
    • For M=-27: RLF changes from 17% (z=1) to 2% (z=5)

Log(1+z)

Jiang, XF et al. 2006b

Mi

outline24
Outline
  • Quasar luminosity function and BH mass function
    • Evolution in accretion properties?
  • Quasar SEDs at high-redshift
    • First signs of cosmic evolution?
  • Star-formation and dust in quasar host galaxies
    • Evolution of M-sigma relation?
  • Probing Reionization with high-redshift quasars
  • Summary
co formation of bh galaxy at high z
Co-formation of BH/Galaxy at high-z
  • Host galaxies of z~6 quasars should have ULIRG properties
    • Star formation rate?
    • Mass of host galaxies?
    • FIR/radio observations:
      • Direct probes of star formation
      • Future: Hershel/ALMA

Li et al. astro-ph/0608190

sub mm and radio observation of high z quasars
Sub-mm and Radio Observationof High-z Quasars
  • Probing dust and star formation in the most massive high-z systems
  • Advantage:
    • No AGN contamination
    • Negative K-correction for both continuum and line luminosity at high-z
    • Give measurements to
      • Star formation rate
      • Gas morphology
      • Gas kinematics
sub mm observations of high z quasars
Sub-mm Observations of High-z Quasars
  • Using IRAM and SCUBA: ~30% of radio-quiet quasars at z>4 detected at 1mm (observed frame) at 1mJy level

 submm radiation in radio-quiet quasars

come from thermal dust

with mass ~ 108 Msun

  • Among z~6 quasars: 5(+2)/19 detected in

submm

  • If dust heating came from starburst

 star formation rate of

500 – 2000 Msun/year

  • Support for star formation origin of

FIR luminosity:

      • z~6 quasars follow starburst galaxy

FIR/radio relation

      • No correlation between FIR and UV
      • Heating source still open question

Arp 220

Bertoldi et al.

submm and co observation of z 6 42 quasar probing the earliest ism
Submm and CO observation of z=6.42 quasar:probing the earliest ISM
  • Strong submm source:
    • Dust T: 50K
    • Dust mass: 7x108 Msun
  • Strong CO source (multiple transitions)
    • Tkin ~ 100K
    • Gas mass: 2x1010 Msun
    • nH2 ~ 105
  • Gas/dust, Temp, density typical of local SB

Bertoldi et al.

cii detection of z 6 42 quasar
[CII] detection of z=6.42 quasar
  • [CII] 158m line:
    • Brightest ISM line
    • Direct probe of SF region
  • J1148 (z=6.42)
    • Both [CII] and LFIR consistent with the brightest local ULIRGs
    • SFR~ 103 Msum

Mailino et al. 2005

high resolution co observation of z 6 42 quasar
High-resolution CO Observation of z=6.42 Quasar

VLA CO 3—2 map

  • Spatial Distribution
    • Radius ~ 2 kpc
    • Two peaks separated by 1.7 kpc
    • CO brightness similar to typical ULIRG SF core.
  • Velocity Distribution
    • CO line width of 280 km/s
    • Dynamical mass within central 2 kpc: ~ 1010 M_sun
    • Total bulge mass ~ 1011 M_sun < M-sigma prediction
  • BH formed before

complete galaxy assembly?

1 kpc

Walter et al. 2004

Channel Maps

60 km/s

m relation at high z
M- relation at high-z
  • Host mass from CO
    • 15 CO detections at z>2
    • Line width all ~200 - 300 km/s
    • Taking at face value:
      • Strong evolution of M-  BH forms early
      • Similar results from HST studies of lensed quasar host (Peng et al.)
  • Caveats:
    • Are luminous quasars biased?
    • Are CO observations biased?
    • Need detailed simulations of dust and gas properties of high-z quasar host galaxies

Shields et al. 2006

summary high z vs low z quasars
Summary: High-z vs. Low-z Quasars
  • LF and BH mass evolution:
    • Flattening of luminosity/mass functions
    • Billion solar mass BH existed at z~6
    • Average Eddington ratio might be increasing at high-z
    • Are high-z and low-z quasars accreting differently?
  • Spectral evolution:
    • Little or no evolution in continuum/emission line properties
    • Strong evolution in radio, Dust and X-ray properties might be evolving as well.
    • Approaching the epoch of AGN structure formation?
  • BH/galaxy co-evolution
    • ISM of high-z quasar hosts similar to that of local ULIRGs
    • narrow CO line width
    • Large BH in small hosts at high-z?
  • Wish list:
    • Larger sample and fainter quasars to break degeneracy
    • Better models/observations in dust/gas
outline34
Outline
  • Quasar luminosity function and BH mass function
    • Evolution in accretion properties?
  • Quasar SEDs at high-redshift
    • First signs of cosmic evolution?
  • Star-formation and dust in quasar host galaxies
    • Evolution of M-sigma relation?
  • Probing Reionization with high-redshift quasars
  • Summary
slide35

reionization

Two Key Constraints:

WMAP 3-yr: zreion=11+/-3

2. IGM transmission: zreion > 6

From Avi Loeb

searching for gunn peterson trough
Searching for Gunn-Peterson Trough
  • Gunn and Peterson (1965)
    • “It is observed that the continuum of the source continues to the blue of Ly-α ( in quasar 3C9, z=2.01)”
    • “only about one part of 5x106 of the total mass at that time could have been in the form of intergalactic neutral hydrogen ”
  • Absence of G-P trough  the universe is still highly ionized
  • First detection of complete G-P trough: SDSS J1030 (z=6.28, Becker et al. 2001)
  • G-P optical depth  evolution of ionizing background and neutral fraction of the IGM
slide38

Keck/ESI 30min exposure 

Gunn-Peterson Trough

in z=6.28 Quasar

Keck/ESI 10 hour exposure 

White et al. 2003

end of reionization epoch open questions
End of Reionization Epoch:Open Questions
  • What’s the Status of IGM at z~6?
    • Measurements of Gunn-Peterson optical depth
    • Evolution of UV background
    • Constraints on IGM neutral fraction
  • Was the Universe mostly neutral by z~6-8?
    • Distribution of dark gaps
    • Evolution of Lyman alpha emitters
  • What is the source of reionization?
accelerated evolution at z 5 7
Optical depth evolution accelerated

z<5.7:  ~ (1+z)4.5

z>5.7:  ~ (1+z)>11

> Order of magnitude increase in neutral fraction of the IGM

 End of Reionization

Dispersion of optical depth also increased

Some line of sight have dark troughs as early as z~5.7

But detectable flux in ~50% case at z>6

End of reionization is not uniform, but with large scatter

Accelerated Evolution at z>5.7

(1+z)11

(1+z)4.5

Fan et al. 2006

ionization state of the igm
Ionization State of the IGM
  • G-P optical depth at z~6:
    • Small neutral fraction needed for complete G-P trough
    • By itself not indication that the object is beyond the reionization epoch
  • The evolution of G-P optical depth:
    • Tracking the evolution of UV background and neutral fraction of the IGM (McDonald & Mirada-Escude 2000)
    • Assuming photoionization:

 ~  2 / 

: IGM overdensity

: photoionizing rate

evolution of ionization state
UV Ionizing background:

Assuming photoionization and model of IGM density distribution

UV background declines by close to an order of magnitude from z~5 to 6.2

Increased dispersion suggests a highly non-uniform UV background at z>5.8

From GP optical depth measurement, volume averaged neutral fraction increase by >~ order of magnitude from z~5.5 to 6.2

Evolution of Ionization State

UV background

Neutral fraction

XF et al. 2006

evolution of proximity zone size around quasars
Evolution of Proximity Zone Size Around Quasars
  • Size of Proximity Zone region

Rp ~ (LQ tQ / fHI )1/3

  • Size of quasar proximity zone decreases by a factor of ~2.4 between z=5.8 and 6.4 (Fan et al. 2006)
  • Consistent with neutral fraction increased by a factor of ~15 over this narrow redshift range
  • But see eg Bolton and Haehnelt (2006) for complications in this intepretation

zem

Haiman, Mesinger, Wyithe, Loeb et al.

Proximity zone size (Mpc)

redshift

Fan et al. 2006

uncertainties in interpretation of proximity zone sizes
Uncertainties in interpretation of proximity zone sizes
  • Bolton & Haehnelt (2006), Maselli et al. (2006)
    • Observed size of proximity zone much smaller than true HII region size
    • Neutral fraction <~ a few percent
    • Consistent with G-P constraints
  • Mesinger et al. (2004), Wyithe et al. (2005)
    • Neutral fraction ~10-30%
  • Better models and simulated spectra needed…

Maselli et al.

2006

Bolton & Haehelt 2006

what ionized the universe agns star formation or else
What ionized the Universe: AGNs, Star Formation or Else

Density of quasars

SFR of galaxies

Bouwens et al.

Exponential decline of quasar

density at high redshift, different

from normal galaxies

Richards et al. 2005,

Fan et al. 2005

reionization by agns
Reionization by AGNs?

XF et al. 2003

  • Can quasars do it?
    • No too few quasars
  • Can low-luminosity AGNs ionize the IGM by z~6?
    • Stacking X-ray image of LBGs in UDF… too few faint AGNs
  • Can accretion to seed BHs ionize the IGM by z~15?
    • Dijkstra, Haiman & Loeb (2004)
    • Soft X-ray background overproduced if quasars produce ~10 photons/H atom
    • ‘Preionization’ to f(HI)~50% by X-rays is still allowed (e.g. Ricotti et al.)

Observerd UV background

Contributions from AGN

Hopkins et al. 2006

slide49

Reionization by stellar sources?

  • Large uncertainties in reionization photon budget:
    • IGM clumpiness
    • UV radiation and escape efficiency
    • Large cosmic variance in deep field data
    • Galaxy luminosity function at high-z

Necessary for reionization 6<z<9 (Stiavelli et al 2003)

Bouwens & Illingworth

surveys of quasars at z 7
Surveys of quasars at z~7

UKIDSS: YJHK photometry

LBT: LBC-Red

i-z-Y selection (1 deg2/night)

y band survey highest redshift qusars and coolest brown dwarfs
Y-band survey: highest-redshift qusars and coolest brown dwarfs

Reionization history: 2 hour on LBT/Lucifer

summary of igm measurements
Summary of IGM Measurements
  • IGM evolution accelerated at z>6
    • Neutral fraction increased by order of mag from z=5.5 to z>6
    • fHI a few percent; IGM not neutral yet at z~6.5
  • IGM evolution is not uniform
    • ~order of mag fluctuation in large scale UV background
  • IGM is not mostly neutral at z~6
    • Transmission spikes in GP trough
  • z~6 marks the end of overlapping stage of an inhomogeneous reionization