# Presentation: 233789

## Evolution of the Highest Redshift Quasars

**Evolution of the Highest Redshift Quasars**

***Xiaohui Fan***
***University of Arizona***

- Collaborators: Becker, Bertoldi, Carilli, Cox,
***Diamond-Stanic***, Hennawi, Ivezic***, Jiang, Kelly***,
- Richards, Schneider, Strauss, ***Vestergaard***, Walter,
- Wang, White, SDSS collaboration

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

##      Quest to the Highest Redshift Quasars

***SDSS***

***Radio***

***CCD***

***IR survey***

**Notes:**

We have been carrying out a survey for high-z quasars using SDSS for the past five-six years.
 Now we have surveyed more than 6000 sq.deg. 
The high-z quasar sample now includes about 1000 quasars at z>4, 
allows us to beat down statistics and study the evolution of population. 
So far we have discovered 19 quasrs at z>5.7. 
The highest is still the 6.42 quasar discovered three years ago. 
The sdss imaging data collection will come to a close in the next couple of seasons. 
We are now using the coadded data in areas with multiple observations 
to push for fainter mag, and hopefully will be able to increase this sample. 

##    The Highest Redshift Quasars Today

- z>4: >1000 known
- z>6: 14
- SDSS i-dropout Survey:
- Completed in June 2006:
***7600 deg******2,  ******z******AB****** < 20***
***25 luminous quasars at 5.7<z<6.4***
- Other on-going z~6 quasar surveys:
***AGES**** (Cool et al.): **Spitzer** **selected**, 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.*

***SDSS******2**** : ***faint quasars in the deep SDSS stripe (****Jiang, XF et al.****), ~10 - 30 additional z~6 quasars in next three years (three z~6 quasar in pilot obs)**

**Notes:**

We have been carrying out a survey for high-z quasars using SDSS for the past five-six years.
 Now we have surveyed more than 6000 sq.deg. 
The high-z quasar sample now includes about 1000 quasars at z>4, 
allows us to beat down statistics and study the evolution of population. 
So far we have discovered 19 quasrs at z>5.7. 
The highest is still the 6.42 quasar discovered three years ago. 
The sdss imaging data collection will come to a close in the next couple of seasons. 
We are now using the coadded data in areas with multiple observations 
to push for fainter mag, and hopefully will be able to increase this sample. 

## Slide 4

**Notes:**
Here are the spectra of the 19 quasars, from 5.74 to 6.42. Note the two 
prominent spectral features: the presence of strong emission lines, 
not only ly a, but also strong metal lines, from N, C, Si etc., indicating
 high metallicity in the quasar env; 
and the strong evolution and complete absorption of ly a forest, 
where the complete or almost complete g-p troughs appear at z>6. 
Now we will discuss the properties in detail. 

## Outline

- Goal: 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-M******sun****** BH?***
- Evolution of quasar luminosity and mass function
***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?***
- Evolution of quasar host galaxies

## 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 massive dark matter halo environment?***
***Assembly of supermassive BHs?***

- Fan et al. 2004

## 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..
- How to assemble such mass BHs and their host galaxies in less than 1Gyr??
- The universe was ~20 tedd old
- Initial assembly from seed BH at z>>10 with non-stop accretion
- Non-trivial for standard thin-disk Eddington-limited accretion
- Low radiative efficiency, super-Eddington or massive seed BH?

- z=6.2

- z=0

- Dark matter

- galaxy

- Springel et al. 2005

## Evolution of Quasar LF Shape

**Evolution of Quasar LF Shape**

- High-z quasar LF different from low-z
- Bright-end slope of QLF is a strong function of redshift
- Transition at z~2.5 (where quasar density peaks in the universe)
***Different formation mechanism at low and high-z?***
***Next step: BH Mass Function (see Vestergaard talk)***

- Richards, et al.; Fan et al. 2006

- NV

- OI

- SiIV

- Ly a

- Ly a forest

***The Lack of Evolution in Quasar Emission Line Properties***

- Fan et al.2004

- Strong metal emission  ***consistent with supersolar metallicity***; rapid chemical enrichment
- Lack of spectral evolution  ***no metallicity evolution***
- Emission line ratio: probing enrichment history
- NV emission  multiple generation of star formation from enriched pops
- Fe II emission  type II SNe... some could be Pop III?
***Does this lack of evolution in rest-frame UV also apply to other wavelength?***

- Nagao et al. 2006

**Notes:**
The other major findings of evolution of the highest z quasars is the striking lack of evolution
 in the spectral energy distribution of quasars, which is in sharp contrast to the strong 
 density evolution, and is highlighted here:
The composite spectrum of z~6 quasars is almost identical to z~0 quasars
 in terms of both slope and emission line strength.
This similarity also extends to other wavelengths, in terms of X-ray, IR and radio prop.
The lack of SED evolution indicates that quasar environment have high metallicity
  and rapid enrichment, and quasar evn matured very early on. 

## Quasar spectral energy distribution

***Spitzer***

-  Dust torus

- Cool Dust in
-   host galaxy

- hot dust

- BLR

- disk

## Hot dust in z~6 Quasars

- To the first order, quasar SEDs are very similar at high and low-z
- 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

- Jiang, XF et al. 2006a

***No hot dust??***

## Where did the hot dust go?

- typical

- J0005

- 8.0m

- 24m

- 5.6m

- 4.8m

- 3.5m

- Host dust contribution

- luminosity

*** ******J0005 (z=5.85):***
-  SED consistent with disk continuum only
-  No similar objects known at low-z
-  ***formation of the first dust ?*** Larger sample...

- Jiang, XF 2006a

## Supernova Dust in z~6 quasar?(Maiolino et al. 2004)

- SDSS J1048 (z=6.2)
- Highest-z Low-BAL
- Typical SED at near UV  moderate dust
- But blue in far-UV
- SED suggesting unusual dust extinction

- Age of the universe < 1Gr
- No time for  dust from evolved low – intermediate mass stars...
- Dust extinction produced by SN dust fits the data

## 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

- Luminosity dependence:
***RLF ~ L******0.5***
- 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)

- Mi

- Jiang, XF et al. 2006b

-       log(radio-loud fraction)

## Lineless quasars: radio quiet BL Lac or quasars with no BLR?

- No emission line, radio-quiet quasars at z>4
- ~1% of high-z quasars
- No obvious low-z counterparts
- No BL Lac signature
- A separate population of quasars?

- Fan et al. 2006

- Ly  distribution

- Diamond-Stanic et al. 2006

***Lineless ***
***Quasars:***
***EW(Ly************)<10***

**Log EW (Ly ********)**

**Notes:**
However, this is not always the case. 
During our high-z quasar survey, we have noticed a class of peculiar quasars:
They have no, or very little, detectable emission lines
But many of them do not show typically features of a beamed source, such as BL Lac,
   including strong ratio/X-ray non-thermal radiation, variability or polarization.
These objects are rare, probably 1% of the high-z population.
The highest redshift example is shown here,  which has an upper limit on the
 Ly a EW of smaller than 5A, while the average is like 70A. 
We don’t really know what they are, but are in the process of carrying out multiwave
 obs to figure it out. See poster. 

## Probing the Host Galaxy Assembly

***Spitzer***

-  Dust torus

- Cool Dust in
-   host galaxy

**Probing the Host Galaxy Assembly**

- Sub-mm and Radio Observation of High-z Quasars
- Probing dust and star formation in the most massive high-z systems; No AGN contamination
- Negative K-correction for both continuum and line luminosity at high-z
- Provides estimates of star formation rate and host ISM properties

## 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

- Mailino et al.  2005

- [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~ 10******3****** M******sum***

## High-resolution CO Observation of z=6.42 Quasar

- 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?***
***Shields et al.: cosmic evolution of M-sigma***
- Are luminous quasars biased?
- Are CO observations biased?
***Need detailed simulations of dust***
***     ******and gas properties of high-z quasar ***
***    ******host galaxies****** ***

- Walter et al. 2004

**1 kpc**

- VLA CO 3—2 map

*********60 km/s*********

- Channel Maps

## Summary: High-z vs. Low-z Quasars

- LF and BH mass evolution:
**Flattening of luminosity functions**
- Billion solar mass BH existed at z~6
**Evolution of accretion rate and mass function? (Vestergaard talk)**
***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? (Shields talk)***
- Wish list:
***Larger sample and fainter quasars to break degeneracy***
***Better models/observations in dust/gas***