AGN Surveys. Phil Outram University of Durham 17 th 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.
University of Durham
17th February 2005
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
Studying QSOs Probes:
In this talk I will outline some of the main results
from the 2dF & SDSS surveys…
0 4000 Åobserved wavelength8000 Å
Croom et al. 2002, MNRAS, 322, L29
Croom et al. 2004, MNRAS, 349, 1397
QSOs selected from imaging in 5 wavebands – u g r i z
Multi-colour selection Sensitive to QSOs at high redshift (z<6.5)
Currently ~50000 QSOs in DR3
i<19 (main sample) i<20 (high-z sample)
Schneider et al. 2003, AJ, 126, 2579
Strong evolution in luminosity density is seen back to z~2.
At z>3 the observed space density of QSOs declines.
Exponential decline of quasar density at high redshift, different from normal galaxies
SFR of Normal Gal
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 FLATTERthan LF at z~2
COMBO-17 luminosity evolution
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 COMBO-17, 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
Croom et al. 2004
Fan et al.
Croom et al. 2004
Decreasing bias upper limit to lifetime of QSOs ≲ 6x108 years at z~2
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 radius-Luminosity relation independent of z then can derive M/L evolution:
Little evolution in M/L seen
This also does not agree with PLE
Large L (R) evolution seen, but what if R ~ M not L??
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… then can derive M/L evolution:
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:
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 Mסּ ~ constant with z
Fewer mergers, less gas around now – fewer, lower L QSOs
On to cosmology… then can derive M/L evolution: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
Fitting model CDM P(k)
Mock QSO P(k) from Hubble Volume ΛCDM N-body simulation
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
An EdS cosmology is rejected at over 95% confidence.
Outram et al. 2004, MNRAS, 348, 745
Myers et al. 2005, submitted
Gaztanaga, 2003, ApJ, 589, 82
Stronger signal seen than expected!
The Ly degenerate… 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 end of reionization epoch??
Fan et al. in prep
Studying QSOs Probes: