Quasars Probing Quasars z = 2.53 b/g QSO z = 2.44 R f/g QSO Quasars Probing Quasars Joseph F. Hennawi Berkeley Hubble Symposium April 20, 2006

Suspects Michael Strauss Scott Burles Jason Prochaska (Princeton) (UCSC) Michael Strauss (Princeton) Scott Burles (MIT)

Outline Primer on quasar absorption lines Proximity effects Fluorescent Ly Emission Anisotropic clustering of absorbers around quasars Shedding light on DLAs

Quasar Absorption Lines Ly Forest Optically thin diffuse IGM / ~ 1-10; 1014 < NHI < 1017.2 well studied for R > 1 Mpc/h Lyman Limit Systems (LLSs) Optically thick 912 > 1 1017.2 < NHI < 1020.3 almost totally unexplored Damped Ly Systems (DLAs) NHI > 1020.3 comparable to disks sub-L galaxies? Dominate HI content of Universe Ly z = 2.96 Lyman Limit Ly z = 2.58 QSO z = 3.0 DLA LLS DLA (HST/STIS) Moller et al. (2003) LLS Nobody et al. (200?) ?

Self Shielding: A Local Example Average HI of Andromeda bump due to M33 LLS Ly forest M31 (Andromeda) M33 VLA 21cm map Braun & Thilker (2004) DLA Sharp edges of galaxy disks set by ionization equilibrium with the UV background. HI is ‘self-shielded’ from extragalactic UV photons. What if the MBH = 3107 M black hole at Andromeda’s center started accreting at the Eddington limit? What would M33 look like then?

Proximity Effects Projected QSO Pair Isolated QSO Neutral Gas Ionized Gas 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?

Cosmology with Quasar Pairs  = 5.4”, z = 2.05; Beam =86-99 kpc/h Close Quasar Pair Survey Discovered ~ 100 sub-Mpc pairs (z > 2) Factor 20 increase in number known ~ 30 systems with beam < 100 kpc/h Moderate Resolution Spectra Keck Gemini-N MMT Near-IR Foreground QSO Redshifts Gemini N-S Science Goals Small scale structure of Ly forest Transverse proximity effects Constrain dark energy from AP test Spectrum from Keck LRIS-B

Fluorescent Emission Shielded HI 912 ~ 1 in self shielding skin UV Background v dist of cloud P(v) Only Ly photons in tail can escape Zheng & Miralda-Escude (2005) In ionization equilibrium ~ 60% of recombinations yield a Ly photon Since 1216 > 104 912 , Ly photons must ‘scatter’ out of the cloud Photons only escape from tails of velocity distribution where Ly is small LLSs ‘reflect’ ~ 60% of UV radiation in a fluorescent double peaked line

Imaging Optically Thick Absorbers Column Density Ly Surface Brightness Cantalupo et al. (2005) Expected surface brightness: Still not detected. Even after 60h integrations on 10m telescopes! or Sounds pretty hard!

Help From a Nearby Quasar Background QSO spectrum 2-d Spectrum of Background Quasar 5700  UV background! Wavelength r = 15.7! DLA trough extended emission Spatial Along Slit (”) Adelberger et al. (2006) Doubled Peaked Resonant Profile?

Why Did Chuck Get So Lucky? b/g QSO Surface brightness consistent with expectation for R|| = 0 R|| constrained to be very small, otherwise fluorescence would be way too dim. DLA must be in this region to see emission f/g QSO R|| R = 280 kpc/h If we assume emission was detected at (S/N) = 10, then (S/N) > 1 requires: R|| < R [(S/N) -1]1/2 = 830 kpc/h or dz < 0.004 Since dN/dz(DLAs) = 0.2, then the probability PChuck = 1/1000! I should spend less time at Keck, and more time in Vegas $$ Chuck Steidel Perhaps DLAs are strongly clustered around quasars?

Absorbers Near Quasars  = 13”, R= 78 kpc/h, gUV = 630  = 16”, R= 97 kpc/h, gUV = 365  = 23”, R= 139 kpc/h, gUV = 420 z = 2.17 z = 2.53 z = 2.07 z = 1.98 z = 2.11 z = 2.44 LLS: NHI = 1019.7 cm-2 LLS: NHI = 1019 cm-2 DLA: NHI = 1020.3 cm-2 Hennawi, Prochaska, et al. (2006)

Anisotropic Clustering Hennawi, Prochaska et al. (2006); Hennawi & Prochaska (2006a) 29 new QSO-LLSs with R < 2 Mpc/h High covering factor for R < 100 kpc/h Assuming T(r) = (r/rT)- and  = 1.6, rT = 9  1.7 (2.9  QSO-LBG) Enhancement over UVB Chuck’s object Absorption probability for LOS as predicted by transverse clustering DLAs from Russell et al. (2006) No clustering z (redshift) = Keck = Gemini = SDSS Transverse clustering predicts every QSO should have an absorber along the LOS = has absorber = no absorber

Proximity Effects: Open Questions There is a LOS proximity effect but not a transverse one. Measured T(r) gives, PChuck = 1/60. Fluorescent emission proves Chuck’s DLA was illuminated. Clustering anisotropy suggests most systems may not be. Two possible sources of clustering anisotropy: QSO ionizing photons are obscured (beamed?) QSOs vary significantly on timescales shorter than crossing time: tcross ~ 4 105 yr at  = 20” (120 kpc/h). Current best limit: tQSO > 104 Can we measure the average opening angle? Yes, but it requires a model for absorbers and QSO-HI clustering. Much easier for optically thin transverse effect (coming soon). Does high covering factor conflict with obscured fractions (~ 30%) of luminous QSOs? Where are the metals from evaporated DLAs/LLSs near QSOs?

Hennawi & Prochaska (2006a) Shedding Light on DLAs QSO is to DLA . . . as . . . O-star is to interstellar cloud Otherwise it is photoevaporated Bertoldi (1989), Bertoldi & Mckee (1989) Cloud survives provided gUV = 5700 b/g QSO f/g QSO R = 280 kpc/h ‘Typical’ numbers for DLA: NHI = 1020.3 cm-2 and r ~ 5 kpc nH ~ 0.01 cm-3 Hennawi & Prochaska (2006a) ionization parameter Survival requires nH > 9 cm-3 r < 11 pc. But Chuck’s fluorescence was resolved in 0.5” seeing r ~ 4 kpc? Two phase medium? Is a disk shielding the galactic halo?

Hennawi & Prochaska (2006b) Got Fluorescence? Hennawi & Prochaska (2006b) gUV = 7900  UVB expect (Chuck’s gUV = 5700) Two other similar systems show no fluorescence ‘Odd’ HI profiles? Unresolved emission? PSF subtracted 2-d spectrum b/g QSO 2-d spectrum f/g QSO  = 6.2”, R= 37 kpc/h background QSO spectrum 3.5 hour integration on Gemini LLS: NHI = 1018.85 cm-2

Summary: Quasars Probing Quasars QSO-absorber pairs probe anisotropy of luminous QSO emission at z > 2. With fluorescents emission, LLSs act as mirrors giving us another view of high redshift QSOs. New measure of the clustering of faint galaxies around quasars. New laboratories to study fluorescent emission. LLSs illuminated by quasars are as bright as Detection of fluorescence constrains quasar lifetime, tQSO > tcross , for individual QSOs! New opportunities to study the distribution of HI in high-z proto-galaxies subject to extreme UV radiation.

Quantifying Absorber Clustering Cosmic Average Transverse Line of Sight b/g QSO isolated QSO cutoff f/g QSO z Far from a QSO z z r R dN/dz only constrains product of number density and cross section. Size does not matter for transverse. It does matter for line of sight. Only rare close pairs probe small scales for transverse. Every isolated line of sight probes small scales.

Close Pairs and the Ly Forest quasar Neutral Gas Goal: Measure transverse Ly correlations of close pairs with z > 2 Science: Extend power spectrum measurements to small scales FWHM Perfect 20 km/s 40 km/s 80 km/s 160 km/s 1 pair at S/N=20 Ability of single pair to distinguish DE = 0.7 from DE = 0.8 (courtesy of Pat McDonald) Measure ‘Jeans Mass’ of Ly clouds thermal history of IGM Probe DE at z ~ 2 with the Alcock - Paczynski test

Small Scale Power at z = 2  = 5.4” z = 2.05, 2.09 Beam =86-99 kpc/h (comoving)

Small Scale Power at z = 3  = 13.8” z = 3.0 Beam =274-306 kpc/h (comoving) Common Absorbers

Tomography with Quasar Groups z = 1.8 z = 2.08 z = 2.17 z = 2.39 8’ z = 2.6 Keck LRIS mask 5’