Download The 2dF QSO Redshift Survey

AGN Surveys
Phil Outram
University of Durham
17th February 2005
Cen A
Type I
Type II
Can observe many different types of AGN in many different wavebands
However, time is short…
So I’ll focus on optically-selected QSO (Luminous Type I AGN) surveys
QSOs and Galaxy Formation
Studying QSOs Probes:
– Accretion history of BHs in the Universe (S. White)
– Relation of BH growth and galaxy evolution
– Large Scale Structure  Cosmology
– State of intergalactic medium
– History of reionization
In this talk I will outline some of the main results
from the 2dF & SDSS surveys…
QSO Surveys
in the last decade
• 1996: Veron-Veron catalogue
– 8609 QSOs
– 2833 AGNs
• 2dF QSO survey (1997 – 2002)
– 25,000 QSOs at z<3
• SDSS QSO survey (1999 – 2005+)
– Currently: >50,000 QSOs
– Goal: 100,000 QSOs
– z<6.5
Selecting QSOs
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QSO candidates selected from multiband optical images
Identity confirmed (+ redshift measured) by spectroscopy
At z<2.5 QSOs typically blue stellar objects
Main contaminants include stars (inc. WDs) + NL galaxies
At low z, host galaxy may make QSO appear extended/redder
z>2.5 Ly forest makes QSO redder
2.5<z<3 QSO colour similar to main sequence stars
Intrinsically reddened / ‘buried’ QSOs may be missed
Trade-off between COMPLETENESS & EFFICIENCY
z=0.1
z=0.3
z=1.3
z=2.0
z=2.5
z=3.0
z=3.8
z=4.5
z=5.0
z=6.43
The 2dF QSO Redshift
Survey
3
Lya
2
CIV
redshift
CIII
MgII
1
OIII
0 4000 Å
observed wavelength
8000 Å
Properties of 2QZ
•QSOs selected from
stellar sources using
U-B:B-R colours
•0.3<z<2.5
•~23000 B<21 QSOs in
final catalogue
•Volume probed
~4 x109h-3Mpc3
www.2dfquasar.org
Croom et al. 2002, MNRAS, 322, L29
Croom et al. 2004, MNRAS, 349, 1397
The 2dF QSO Redshift Survey
The SDSS QSO Survey
NGP
SGP
QSOs selected from imaging in
5 wavebands – u g r i z
Multi-colour selection 
Sensitive to QSOs at high
redshift (z<6.5)
Schneider et al. 2003, AJ, 126, 2579
Currently ~50000 QSOs in DR3
i<19 (main sample) i<20 (high-z sample)
www.sdss.org
Evolution of Quasar
Luminosity Function
Strong evolution in
luminosity density is seen
back to z~2.
SFR of Normal Gal
At z>3 the observed space
density of QSOs declines.
Exponential decline of
quasar density at high
redshift, different from
normal galaxies
Evolution of LF shape
PDE
PLE
At low-z: LF is well fit by double power law with pure luminosity
evolution
PLE  A single population of rare, long-lived QSOs?
At z~4: quasar
luminosity function
much FLATTER than
LF at z~2
COMBO-17
Due to the relatively bright
magnitude limits of the SDSS
and 2QZ surveys, the LF
analysis is restricted to relatively
bright QSOs – especially at high
redshift.
What about fainter QSOs?
2SLAQ survey extending 2QZ a
magnitude deeper:~10000
g<21.85 QSOs on the way…
Photometric selection of 192
1.2<z<4.8 QSOs using COMBO17, reaching R~24
Wolf et al. (2003)
The evolving LF can be adequately described by either PLE (dashed line) or PDE
(solid line) – largely due to the absence of an obvious break
QSO Clustering
Do QSOs trace:
 the large scale structure of dark matter,
 the distribution of normal galaxies, or,
 just the most overdense regions (a
highly-biased distribution)?
We can answer this question by
determining the amplitude of QSO
clustering 
The 2-Point Correlation Function
Croom et al. 2004
Redshift Evolution
2dF
Croom et al. 2004
Fan et al.
Decreasing bias  upper limit to lifetime of QSOs ≲ 6x108 years at z~2
2dF QSO
clustering
amplitude at
fixed z vs
MB
(Loaring et al. in prep)
BLR Emission Line Widths
Measure v & apply virial theorem:
MBH ~ R v 2
Assume: R ~ L 0.68
- observed locally (Netzer 2002)
where R is the BLR radius.
MBH ~ v 2 L 0.68
Line widths  MBH ~ L0.93
Corbett et al 2003, MNRAS, 343, 705
Assuming that radiusLuminosity relation
independent of z then can
derive M/L evolution:
Little evolution in M/L seen
This also does not agree
with PLE
Caveat…
Large L ( R) evolution
seen, but what if R ~ M not
L??
Evolution in BH mass function
McLure & Dunlop 2003
QSO BH masses appear to drop towards lower redshift! (“Downsizing”)
However… Direct imaging  host galaxies do not appear any larger at
high redshift (e.g. Croom et al 2004)
Understanding QSOs: summary of evidence so far…
Locally: QSOs cluster like average galaxies
z~2: higher clustering amplitude + MUCH more luminous / numerous
Little correlation between luminosity / clustering amplitude
QSOs seen out to z>6
LF well described by PLE
QSO BH mass  as z  ?
BHs seen in ALL bulges – tight correlation:
Possible scenario…
In hierarchical galaxy merging paradigm - all major galaxies have short-lived QSO
phase:
QSO lit up when gas funnelled into galaxy centre after merger
QSO stage when halo has mass ~ 1012-13 M‫ ~ סּ‬constant with z
Fewer mergers, less gas around now – fewer, lower L QSOs
 Semi-Analytic models
On to cosmology…
The 2QZ Power Spectrum
Need to assume
cosmology to
derive r from z
Power spectra
convolved with
survey window
functions
Outram et al. 2003,
MNRAS, 342, 483
Comparison with models
Fitting model CDM P(k)
Mock QSO P(k) from
Hubble Volume ΛCDM
N-body simulation
Ωmh=0.19±0.05 Ωb/Ωm=0.18±0.10
Redshift-space Distortions in the
QSO Power Spectrum
Outram et al. 2001, MNRAS, 328, 174
z-space distortion effect of cosmology / infall degenerate…
However, we have a second constraint on the bias (and hence
infall) from the correlation function analysis
Ωm=1-ΩΛ=0.29
β=0.45
+0.17
-0.09
+0.09
-0.11
An EdS cosmology
is rejected at over
95% confidence.
Outram et al. 2004, MNRAS, 348, 745
Gravitational lensing of distant
QSOs by foreground galaxies
Cross-correlation of QSOs
with foreground galaxies
Myers et al. 2005, submitted
Gaztanaga, 2003, ApJ, 589, 82
Stronger signal seen than expected!
The Ly Forest Power
Spectrum
Optical depth fluctuations in
observed spectra monotonically
mapped onto a Gaussian density
field.
Bias-free linear P(k) estimate at
2<z<5
McDonald et al. (2004)
3000 SDSS spectra
Kim et al. (2004) –
LUQAS QSOs
from UVES - 27
high-resolution
QSO spectra
Large uncertainty in normalization due to uncertainty in continuum &
hence optical depth – especially in low resolution spectra.
The Highest Redshift QSOs
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z>4: ~700 known
z>5: ~30
z>6: 7
SDSS i-dropout Survey:
– By Spring 2004: 6000
deg2 at zAB<20
– Fourteen luminous
quasars at z>5.7
• 20 – 40 at z~6 expected in
the whole survey
Total Discoveries
SDSS Discoveries
Constraining the
Reionization Epoch
• Neutral hydrogen fraction
– Volume-averaged HI fraction
increased by >100 from z~3 to
z~6
– Mass-averaged HI fraction > 1%
mass ave.
• At z~6:
– Last remaining neutral regions
are being ionized
– The universe is >1% neutral
The end of reionization
epoch??
vol. ave
Fan et al. in prep
QSOs and Galaxy Formation
Studying QSOs Probes:
– Accretion history of BHs in the Universe
– Relation of BH growth and galaxy evolution
– Large Scale Structure  Cosmology
– State of intergalactic medium
– History of reionization