1 / 35

Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies

Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies. Joseph F. Hennawi UC Berkeley. Ohio State February 20, 2007. Suspects. Xavier Prochaska (UCSC). Scott Burles (MIT). Juna Kollmeier (Carnegie) & Zheng Zheng (IAS). Outline. Motivation Finding close quasar pairs

shanai
Télécharger la présentation

Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Quasars Probing Quasars: Shedding (Quasar) Light on High Redshift Galaxies Joseph F. Hennawi UC Berkeley Ohio State February 20, 2007

  2. Suspects Xavier Prochaska (UCSC) Scott Burles (MIT) Juna Kollmeier (Carnegie) & Zheng Zheng (IAS)

  3. Outline • Motivation • Finding close quasar pairs • IGM Primer • Quasar-Absorber Clustering • Fluorescent Ly Emission Bottom Line: The physical problem of a quasar illuminating an optically thick cloud of HI is very simple compared to other problems in galaxy formation.

  4. Motivation

  5. A Simple Observation Spectrum from Wallace Sargent

  6. Quasars Evolution for Poets Progenitors Relics Richards et al. (2006) Tremaine et al. (2002) Comoving Number Density z (redshift) Dramatic evolution of number density/ luminosity Boyle et al. (2001) L*(z)/L*(0) look back time

  7. Quasar Evolution for Pundits AGN unified model Barger et al. (2005) unidentified BLAGN Steffen et al. (2003) non-BLAGN The AGN unified model breaks down at high luminosities. “Almost all luminous quasars are unobscured . . . ”

  8. HI in High Redshift Galaxies? M33 HI/H/Optical M33 HI/CO Radial CO and HI profiles for 7 nearby galaxies (Wong & Blitz 2002). 106 M 3105 M 105 M Engargiola et al. (2002) Image credit: Fabian Walter • The HI is much more extended than the stars and molecular gas. • Until SKA, no way to image HI at high redshift. • HI is what simulations of galaxy formation might predict (reliably).

  9. The Power of Large Surveys Apache Point Observatory (APO) ARC 3.5m Jim Gunn • Spectroscopic QSO survey • 5000 deg2 • 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 deg2 • 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 MMT 6.5m Follow up QSO pair confirmation from ARC 3.5m and MMT 6.5m

  10.  = 3.7” 55” Excluded Area Finding Quasar Pairs low-z QSOs 2’ 2.0 2.0 3.0 4.0 3.0 SDSS quasar @ z =3.13 2.0 4.0 3.0

  11. 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 Ly Forest Correlations Normalized Flux CIV Metal Line Correlations Keck MMT Gemini-S 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  = 13.8”, z = 3.00; Beam =79 kpc/h Spectra from Keck ESI Collaborators: Jason Prochaska, Crystal Martin, Sara Ellison, George Djorgovski, Scott Burles, Michael Strauss

  12. IGM Primer

  13. Lyman Limit z = 2.96 Ly z = 2.96 Ly z = 2.58 LLS DLA (HST/STIS) DLA LLS ? Moller et al. (2003) Nobody et al. (200?) 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 QSO z = 3.0

  14. Self Shielding: A Local Example Average HI of Andromeda bump due to M33 LLS Ly forest M33 VLA 21cm map M31 (Andromeda) 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?

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

  16. Fluorescent Ly 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 (2002) • 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

  17. 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!

  18. Help From a Nearby Quasar Background QSO spectrum 2-d Spectrum of Background Quasar Transverse flux = 5700  UVB! Wavelength DLA trough r = 15.7! 11 kpc 4 kpc f/g QSO extended emission Spatial Along Slit (”) Adelberger et al. (2006) R = 384 kpc Doubled Peaked Resonant Profile?

  19. I should spend less time at Keck, and more time in Vegas $$ Chuck Steidel 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! Perhaps DLAs are strongly clustered around quasars?

  20. Quasar-Absorber Clustering

  21. Quasars Probing Quasars Hennawi, Prochaska, et al. (2007)

  22. Transverse Clustering Hennawi, Prochaska et al. (2007); Hennawi & Prochaska (2007) Enhancement over UVB Chuck’s object • 29 new QSO-LLSs with R < 2 Mpc/h • High covering factor for R < 100 kpc/h • For T(r) = (r/rT)-,  = 1.6, and NHI > 1019 cm-2, rT = 9  1.7 (2.9  QSO-LBG)  = 2.0  = 1.6 QSO-LBG z (redshift) = SDSS = Keck = Gemini = has absorber = no absorber

  23. Proximate DLAs: LOS clustering Prochaska, Hennawi, & Herbert-Fort (2007) • Found 12 PDLAs out of ~ 2000 z < 2.7 quasars • Transverse clustering strength at z = 2.5 predicts that nearly every QSO should have an absorber with NHI > 1019 cm-2 along the LOS?? • Rapid redshift evolution of QSO clustering compared to paucity of proximate DLAs implies that photoevaporation has to be occurring.

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

  25. Proximity Effects: Summary • There is a LOS proximity effect but not a transverse one. • Photoevaporation plausible for absorbers near quasars. • Our measured T(r) gives, PChuck = 1/65. • Fluorescent emission proves Chuck’s DLA was illuminated. • Clustering anisotropy suggests transverse systems are not. • 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 @  = 20” (120 kpc/h). Current limit: tQSO > 104 yr

  26. Proximity Effects: Open Questions • Can we measure the average opening angle? • Yes, but must model photoevaporation assuming an absorber density profile. • Much easier for optically thin transverse effect (coming soon). • Does high transverse covering factor conflict with obscured fractions (~ 10%) of luminous QSOs? • Why did Chuck’s DLA survive whereas others are photoevaporated?

  27. Fluorescent Ly Emission

  28. Transverse Fluorescence? PSF subtracted 2-d spectrum (Data-Model)/Noise Implied transverse ionizing flux gUV = 6370  UVB! b/g QSO z = 3.13 2-d spectrum f/g QSO z = 2.29 background QSO spectrum Hennawi, Prochaska, & Burles (2007)

  29. Near-IR Quasar Redshifts

  30. Transverse Fluorescence? PSF subtracted 2-d spectrum (Data-Model)/Noise Implied transverse ionizing flux gUV = 7870  UVB! b/g QSO z = 2.35 2-d spectrum f/g QSO z = 2.27 metals at this z Background QSO spectrum Hennawi, Prochaska, & Burles (2007)

  31. Ly Emission from DLAs Intervening DLAs HST STIS Image 2-d Spectrum Proximate DLAs Could the proximate DLA emission be fluorescence excited by the quasar ionizing flux? Moller et al. (2004)

  32. b/g QSO Proximate Absorber Full Moon? Absorber f/g QSO Fluorescent Phases Transverse f/g QSO R b/g QSO Absorber

  33. A Fluorescing PDLA? b/g QSO R|| DLA Hennawi, Kollmeier, Prochaska, & Zheng (2007) • Ly brighter than 95% of LBGs --- unlikely to be star formation. • Detection of N(N+4) > 1014.4 cm-2 consistent with hard QSO spectrum and requires R|| < 700 kpc. • Large fLy = 4.310-16 erg s-1 cm-2 suggests R|| ~ 300 kpc. • If emission is Ly from QSO halo, then we can image DLA in silhouette.

  34. New Probes of HI in High-z Galaxies Fluorescent Ly Emission Statistics of PDLAs Ly Emissivity Map Aperture Spectra Photo-evaporation of DLAs Column distribution near QSOs Hennawi, Kollmeier, Prochaska, & Zheng (2007) Hennawi, Prochaska, & Herbert-Fort (2007) • These observables are predictable given a model for HI distribution in high-z galaxies. • The physics of self-shielding and resonant line radiative transfer are straightforward compared to other problems in galaxy formation.

  35. Summary • With projected QSO pairs, QSO environments can be studied down to ~ 20 kpc where ionizing fluxes are as large as 104 times the UVB. • Clustering pattern of absorbers around QSOs is highly anisotropic. • Rapid redshift evolution of QSO clustering compared to paucity of proximate DLAs implies that photoevaporation has to be occuring. • Physical arguments indicate that DLAs within 1 Mpc of a luminous quasar can be photoevaporated. • QSO-LLS pairs provide new laboratories to study Ly fluorescence. • Null detections of fluorescence and clustering anisotropy suggest that quasar emission is either anisotropic or variable on timescales < 105 yr. • Photoevaporation and fluorescent emission provide new physical constraints on the distribution of HI in high-z proto-galaxies. The input physics is relatively simple and it can be easily modeled.

More Related