AGN Surveys Phil Outram University of Durham 17 th February 2005

Cen A 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 Type I Type II

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 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 CIII MgII 1 OIII Å observed wavelength 8000 Å redshift

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 x10 9 h -3 Mpc 3 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) Currently ~50000 QSOs in DR3 i<19 (main sample) i<20 (high-z sample) Schneider et al. 2003, AJ, 126,

Evolution of Quasar Luminosity Function SFR of Normal Gal 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

Evolution of LF shape PLEPDE

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

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 <z<4.8 QSOs using COMBO- 17, reaching R~24 Wolf et al. (2003) COMBO-17

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 Croom et al 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

Redshift Evolution 2dF Fan et al. Croom et al Decreasing bias  upper limit to lifetime of QSOs ≲ 6x10 8 years at z~2

2dF QSO clustering amplitude at fixed z vs M B (Loaring et al. in prep)

BLR Emission Line Widths Corbett et al 2003, MNRAS, 343, 705 Measure v & apply virial theorem: M BH ~ R v 2 Assume: R ~ L observed locally (Netzer 2002) where R is the BLR radius.  M BH ~ v 2 L 0.68 Line widths  M BH ~ L 0.93

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 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 ~ M סּ ~ constant with z Fewer mergers, less gas around now – fewer, lower L QSOs  Semi-Analytic models

Outram et al. 2003, MNRAS, 342, 483 Need to assume cosmology to derive r from z Power spectra convolved with survey window functions On to cosmology… The 2QZ Power Spectrum

Comparison with models Mock QSO P(k) from Hubble Volume ΛCDM N-body simulation Fitting model CDM P(k) Ω m h=0.19±0.05 Ω b /Ω m =0.18±0.10

Redshift-space Distortions in the QSO Power Spectrum Outram et al. 2001, MNRAS, 328, 174

Ω m =1-Ω Λ =0.29 β=0.45 Outram et al. 2004, MNRAS, 348, An EdS cosmology is rejected at over 95% confidence. 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

Gravitational lensing of distant QSOs by foreground galaxies

Cross-correlation of QSOs with foreground galaxies Myers et al. 2005, submittedGaztanaga, 2003, ApJ, 589, 82 Stronger signal seen than expected!

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 The Ly  Forest Power Spectrum

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 z>4: ~700 known z>5: ~30 z>6: 7 SDSS i-dropout Survey: –By Spring 2004: 6000 deg 2 at z AB <20 –Fourteen luminous quasars at z> – 40 at z~6 expected in the whole survey SDSS Discoveries Total 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% At z~6: –Last remaining neutral regions are being ionized –The universe is >1% neutral The end of reionization epoch?? Fan et al. in prep mass ave. vol. ave

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