1. Joseph F. Hennawi UC Berkeley & OSU October 3, 2007 Xavier Prochaska (UCSC) Quasars Probing Quasars

2. A Simple Observation Spectrum from Wallace Sargent

3. The Basic Picture HI cloud Line-of-Sight QSO Transverse b/g QSO f/g QSO R || RR HI cloud Ly  absorption can probe 8 decades in N HI (  Ly  is large!). Neighboring sightline provides a another view of the QSO. Redshift space distortions from kT motions (~ 20 km/s ) smooth with Gaussian of R prop ~ 60 kpc = 10 ” @ z = 2. Need projected QSO pairs to study small scales!

4. What Can Proximity Effects Teach Us? How is HI distributed around quasars? What is the quasar duty cycle  t QSO /t H  ? What is the obscured fraction (1- Ω/4  )? Can we constrain episodic QSO variability, t burst ? Directly observe impact of AGN feedback on the IGM? Physics of IGM well understood no sub-grid physics or semi-analytical recipes!

5. Mining Large Surveys Apache Point Observatory (APO) Spectroscopic QSO survey –5000 deg 2 –45,000 z < 2.2; i < 19.1 –5,000 z > 3; i < 20.2 –Precise (u,g,r, i, z) photometry Photometric QSO sample –8000 deg 2 –500,000 z < 3; i < 21.0 –20,000 z > 3; i < 21.0 –Richards et al. 2004; Hennawi et al. 2006 SDSS 2.5m ARC 3.5m Jim Gunn Follow up QSO pair confirmation from ARC 3.5m and MMT 6.5m MMT 6.5m

6.  = 3.7” 2’ 55” Excluded Area Finding Quasar Pairs SDSS QSO @ z =3.13 4.0 2.0 3.0 2.0 3.0 2.0 4.0 low-z QSOs f/g QSO z = 2.29 b/g QSO z = 3.13 Keck LRIS spectra (Å)

7. Cosmology with Quasar Pairs Close Quasar Pair Survey Discovered > 100 sub-Mpc pairs (z > 2) Factor 25 increase in number known Moderate & Echelle Resolution Spectra Near-IR Foreground QSO Redshifts About 50 Keck & Gemni nights.  = 13.8”, z = 3.00; Beam =79 kpc/h Spectra from Keck ESI Keck Gemini-N Science Dark energy at z > 2 from AP test Small scale structure of Ly  forest Thermal history of the Universe Topology of metal enrichment from Transverse proximity effects Gemini-S Collaborators: Jason Prochaska, Crystal Martin, Sara Ellison, George Djorgovski, Scott Burles Ly  Forest Correlations CIV Metal Line Correlations Normalized Flux

8. Quasar Absorption Lines DLA (HST/STIS) Moller et al. (2003) LLS Nobody et al. (200?) Ly  z = 2.96 Lyman Limit z = 2.96 QSO z = 3.0 LLS Ly  z = 2.58 DLA Ly  Forest – –Optically thin diffuse IGM – –  /  ~ 1-10; 10 14 < N HI < 10 17.2 – –well studied for R > 1 Mpc/h Lyman Limit Systems (LLSs) – –Optically thick  912 > 1 – –10 17.2 < N HI < 10 20.3 – –almost totally unexplored Damped Ly  Systems (DLAs) – –N HI > 10 20.3 comparable to disks – –sub-L  galaxies? – –Dominate HI content of Universe

9. Self Shielding: A Local Example Sharp edges of galaxy disks set by ionization equilibrium with the UV background. HI is ‘self-shielded’ from extragalactic UV photons. Braun & Thilker (2004) M31 (Andromeda) M33 VLA 21cm map DLA Ly  forest LLS What if the M BH = 3  10 7 M  black hole at Andromeda’s center started accreting at the Eddington limit? What would M33 look like then? bump due to M33 Average HI of Andromeda

10. Neutral Gas Isolated QSO Proximity Effects Proximity Effect  Decrease in Ly  forest absorption due to large ionizing flux near a quasar Transverse Proximity Effect  Decrease in absorption in background QSO spectrum due to transverse ionizing flux of a foreground quasar – –Geometry of quasar radiation field (obscuration?) – –Quasar lifetime/variability – –Measure distribution of HI in quasar environments Are there similar effects for optically thick absorbers? Ionized Gas Projected QSO Pair

11. Transverse Optically Thick Hennawi, Prochaska, et al. (2007) z bg = 3.13; z fg = 2.29; R  = 22 kpc/h; logN HI = 20.5 z bg = 2.07; z fg = 1.98; R  = 139 kpc/h; logN HI = 19.0 z bg = 2.21; z fg = 2.18; R  = 61 kpc/h; logN HI = 18.5 z bg = 2.53; z fg = 2.43; R  = 78 kpc/h; logN HI = 19.7 z bg = 2.35; z fg = 2.28; R  = 37 kpc/h; logN HI = 18.9 z bg = 2.17; z fg = 2.11; R  = 97 kpc/h; logN HI = 20.3

12. Transverse Optically Thick Clustering Hennawi, Prochaska et al. (2007); Hennawi & Prochaska (2007) = Keck = Gemini = SDSS = has absorber= no absorber Enhancement over UVB z (redshift)  = 2.0  = 1.6 QSO-LBG 29 new QSO-LLSs with R < 2 Mpc/h High covering factor for R < 100 kpc/h For  T (r) = (r/r T ) - ,  = 1.6, log N HI > 19 r T = 9  1.7 Mpc/h (3  QSO-LBG)

13. Line-of-Sight Clustering Prochaska, Hennawi, & Herbert-Fort (2007) Factor 5-10 fewer PDLAs then expected from transverse clustering. Transverse clustering strength at z = 2.5 predicts that ~ 90% of QSO’s should have an absorber with N HI > 10 19 cm -2 along the LOS?? Rapid redshift evolution of QSO clustering compared to paucity of proximate DLAs implies that photoevaporation has to be occurring. Transverse prediction 1 +  || (∆v) z Line-of-Sight Clustering Strength Extrapolation of trans. predictions Line-of-sight measurements Proximate DLA  DLA within  v < 3000 km/s

14. Photoevaporation f/g QSO b/g QSO RR QSO is to DLA... as... O-star is to interstellar cloud Hennawi & Prochaska (2007a) Otherwise it is photoevaporated Bertoldi (1989), Bertodi & McKee (1989) Cloud survives provided r = 17 r = 19 r = 21 n H = 0.1 log N HI = 20.3

15. Emission Anisotropy Obscuration/Beaming f/g QSO b/g QSO Absorber RR  > 10 4 yr Episodic Variability  QSO’s vary significantly on timescale t 10 4 yr. Episodic Variability f/g QSO b/g QSO Absorber We observe light emitted at time t = t 0 Ionization state of gas depends on QSO at time t = t 0 - R  /c RR t = t 0

16. Optically Thick LLSs and DLAs (today’s talk) –Nature of absorbers near QSO’s is unclear. Gas entrained from AGN driven outflow? (AGN feedback!) Absorption from nearby dwarf galaxies? –To measure  t QSO /t H  or (Ω/4  ) we need to model absorbers and do radiative transfer (hard). Optically Thin Ly  Forest (in progess) –Best for constraining  t QSO /t H  and (Ω/4  ). –Why? Because we can predict the Ly  forest fluctuations ab initio from N-body simulations (easy). Proximity Effects: Thick and Thin

17. Optically Thin (Sneak Preview) Hennawi, et al. (2007), in prep = Gemini = accurate z= no accurate z Enhancement over UVB z (redshift) Sample 1.6 < z < 4.5; 20 kpc < R < 10 Mpc 59 pairs with g UV > 100. 30 accurate near-IR redshifts. (  m ),, = Keck, = SDSS z = 2.4360  z = 44 km/s Gemini NIRI K-band spectrum

18. Transverse Proximity Effect? z = 3.8135  z = 44 km/s z bg = 4.11, z fg = 3.81  = 34”, R  = 175 kpc/h t cross = 5.7  10 7 yr g UV = 626! with f/g QSO without f/g QSO Real Simulated Hennawi et al. 2007, in prep. Gemini NIRI K-band spectrum Spectrum from Keck ESI

19. Summary With projected pairs, QSO environments can be probed down to ~ 20 kpc where ionizing flux is ~ 10 4 times the UVB. Clustering of optically thick absorbers around QSOs is highly anisotropic. Paucity of PDLAs implies photoevaporation has to occur. Physical arguments indicate DLAs < 1 Mpc from a QSO can be photoevaporated. T here is a LOS optically thick proximity effect but no transverse one. Either QSOs emit anisotropically or are variable on timescales < 10 6 yr. The optically thin proximity effect will distinguish between these two possibility and yield new quantitative constraints.