Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Hubble Fellowship Symposium April 2, 2007
Suspects Jason X. Prochaska (UCSC) Juna Kollmeier (Carnegie) & Zheng Zheng (IAS) Hubble Fellow Class of 2001 Hubble Fellow Classes of 2006 and 2004
Outline Finding close projected quasar pairs IGM Physics Primer Fluorescent Ly Emission Bottom Line: The physical problem of a quasar illuminating a high redshift galaxy is very simple compared to other problems in galaxy formation.
The AGN Unified Model BLAGN Steffen et al. (2003) unidentified non-BLAGN The AGN unified model breaks down at high luminosities. “Nearly all (~ 90%) luminous quasars are unobscured... ” Barger et al. (2005) AGN unified model BLAGN obscured non-BLAGN
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 SDSS 2.5m ARC 3.5m Jim Gunn Follow up QSO pair confirmation from ARC 3.5m and MMT 6.5m MMT 6.5m
= 3.7” 2’ 55” Excluded Area Finding Quasar Pairs SDSS z = low-z QSOs f/g QSO z = 2.29 b/g QSO z = 3.13 Keck LRIS spectra (Å)
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 45 Keck & Gemni nights. 8 MMT 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 Transverse proximity effects Gemini-S MMT Collaborators: Jason Prochaska, Crystal Martin, Sara Ellison, George Djorgovski, Scott Burles, Michael Strauss Ly Forest Correlations CIV Metal Line Correlations Normalized Flux
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; < N HI < –well studied for R > 1 Mpc/h Lyman Limit Systems (LLSs) –Optically thick 912 > 1 – < N HI < –almost totally unexplored Damped Ly Systems (DLAs) –N HI > comparable to disks –sub-L galaxies? –Dominate HI content of Universe
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
Fluorescent Ly Emission In ionization equilibrium ~ 60% of recombinations yield a Ly photon Since 1216 > 10 4 912, Ly photons must ‘diffuse’ out of the cloud Photons only escape from tails of velocity distribution where Ly is small LLSs ‘reflect’ ~ 60% of UV continuum in a fluorescent double peaked line Zheng & Miralda-Escude (2002) In self shielding skin 912 ~ 1; Ly ~ 10 4 Self-Shielded HI UV Background Only Ly photons in tail can escape P(x) Escape Probability Resonant Line Emission Profile x
Imaging Optically Thick Absorbers Cantalupo et al. (2005) Column Density Ly Surface Brightness Expected surface brightness: Still not detected. Even after 60h integrations on 10m telescopes! or Sounds pretty hard!
Help From a Nearby Quasar Adelberger et al. (2006) DLA trough 2-d Spectrum of Background Quasar Spatial Along Slit (”) Wavelength extended emission r = 15.7! Doubled Peaked Resonant Profile? Background QSO spectrum Transverse flux = 5700 UVB! f/g QSO R = 384 kpc 11 kpc 4 kpc
Transverse Fluorescence? Implied transverse flux g UV = 6370 UVB! f Ly < 4 erg/cm 2 /s Could detect signal to R || < 7.5 R = 170 kpc/h background QSO spectrum 2-d spectrum f/g QSO z = 2.29 PSF subtracted 2-d spectrum (Data-Model)/Noise Hennawi & Prochaska (2007) b/g QSO z = hours Keck LRIS-B f/g QSO R || b/g QSO R = 22 kpc/h Probability of null detection: P( =4 ) = 9% P( =2 ) = 77%
Near-IR Quasar Redshifts
Transverse Fluorescence? metals at this z Background QSO spectrum 2-d spectrum f/g QSO z = 2.27 PSF subtracted 2-d spectrum (Data-Model)/Noise Hennawi & Prochaska (2007) b/g QSO z = hours Gemini GMOS Implied ionizing flux g UV = 7870 UVB! f Ly < 5 erg/cm 2 /s Could detect signal to R || < 7.8 R = 295 kpc/h f/g QSO R || b/g QSO R = 38 kpc/h near-IR f/g z Probability of null detection: P( =4 ) = 5% P( =2 ) = 76%
Punchline With projected QSO pairs, QSO environments can be studied down to ~ 20 kpc where ionizing fluxes are as large as 10 4 times the UVB. QSO-absorber pairs provide new laboratories to study Ly fluorescent emission without at 30m telescope. RR f/g QSO b/g QSO Absorber Aperture Spectra Ly Emissivity Kollmeier et al. (2007); Hennawi, Kollmeier, Prochaska, & Zheng (2007) The physics of self-shielding and Ly resonant line radiative transfer are very simple compared to other problems in galaxy formation.