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Quasar Absorption Lines at High Redshift: Through a Glass Darkly

Quasar Absorption Lines at High Redshift: Through a Glass Darkly. Steve Furlanetto Caltech March 18, 2005. Collaborators: L. Hernquist, A. Loeb, S.P. Oh, M. Zaldarriaga. The Ly a Forest at High Redshifts. Ly a forest saturates at z~6!

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Quasar Absorption Lines at High Redshift: Through a Glass Darkly

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  1. Quasar Absorption Lines at High Redshift: Through a Glass Darkly Steve Furlanetto Caltech March 18, 2005 Collaborators: L. Hernquist, A. Loeb, S.P. Oh, M. Zaldarriaga

  2. The Lya Forest at High Redshifts • Lya forest saturates at z~6! • What have QSO spectra taught us about reionization? • What can we pull out of QSO spectra at z>6? • Transmission spikes in Lyman-series • Metal absorption lines Becker et al. (2001)

  3. SDSS Quasars • SDSS J1030 (z=6.28) • No flux for z=6.2-5.98 in Ly or Ly • >9.9 (2mean effective value) White et al. (2003)

  4. J1030: Mean Properties • Measured  +IGM model  estimate of ionization rate (assuming uniform) • Appears to change more rapidly at z=6 • Difficult to constrain xHI because only probes deep voids • End of reionization? • Caveat: poor statistics! (Paschos & Norman 2004) Fan et al. (2001)

  5. Lyman-series Optical Depths Quasar • When integrating over large path length, must include cosmic web • Transmission samples unusually underdense voids • Requires model for density distribution! • Extremely difficult to measure xHI! • Different lines sample different densities Filament Visible in Ly Visible in Ly Observer

  6. Lyman-series Optical Depths • When integrating over large path length, must include cosmic web • Transmission samples unusually underdense voids • Requires model for density distribution! • Extremely difficult to measure xHI! • Different lines sample different densities Oh & Furlanetto (2005)

  7. SDSS Quasars • SDSS J1148 (z=6.42) • Transmission spikes in Ly, Ly troughs • Residual flux elsewhere • CIV absorber at z=5 • Ly emission lines (w/in 1000 km/s)? • Faint continuum? White et al. (2003)

  8. The Case Against AnInterloper: Residual Flux Ly at z=5 Residual flux (5) Flux White et al. (2003) • Transmission spikes abruptly stop at z=6.33 for Ly (Oh & Furlanetto 2005) • No continuum break past Ly for z=5 galaxy (Oh & Furlanetto 2005)

  9. The IGM Toward J1148+5251 Ly at z=6.33 Ly at z=5 Residual flux (5) Flux White et al. (2003) • Residual flux originates at quasar (Oh & Furlanetto 2005) • Allows measurement of  < 15.4 (2), likely ~7-11, at z=6.18-6.32 (uncertainty is in IGM density model) • IGM is still highly ionized! • SDSS J1030+0524 requires >9.9 (2) • Difference stronger where transmission spikes appear • Large cosmic variance in reionization!

  10. The Topology of Reionization 13 comoving Mpc z=8.74 • Simple semi-analytic models treat HII regions around individual galaxies • Simulations show clustering drives evolution! z=7.24 Sokasian et al. (2003)

  11. Bubble Sizes xH=0.96 xH=0.70 xH=0.25 SF, MZ, LH (2004a)

  12. Bubble Sizes: How Big? • For bubble to grow, ionizing photons must reach bubble wall • Mean free path depends on density structure of IGM (xH ~ 2) • Limit kicks in when R>10-30 Mpc (Furlanetto & Oh, in prep)

  13. QSO Spectra Flux White et al. (2003) • What are these transmission spikes? • Post-reionization features? • Voids? • Bubbles?

  14. For transmission: Must eliminate resonant absorption: pass close to ionizing source Must eliminate damping wing absorption: pass through large HII region For isolated galaxies, NO features before reionization (Barkana 2002) Transmission Spikes QSO QSO IGM HI

  15. QSO Absorption Spectra • Include clustering of sources: eliminate damping wing absorption • Curves have xH=(0.1,0.15,0.2,0.25) at z=6.1 • Simple model: • Includes inhomogeneous IGM • Naïve distribution of sources within bubbles • No recombinations • Can we probe mid/late stages of reionization with QSO/GRB spectra? Observed Feature SF, LH, MZ (2004)

  16. Studying the IGM Structure • Mean free path ultimately constrained by dense neutral blobs (?) • Left to right: max mfp=(10, 20, 30, 60, 600) comoving Mpc (all at xi=0.96) • Are we interpreting the tail end of reionization properly? SF, SPO (in prep)

  17. Complex Reionization Wyithe & Loeb (2003) • WMAP: ~0.17; reionization begins early • SDSS: reionization ends at z=6 • Reconcile through complicated source physics: Feedback!, e.g. • Photoionization • Minihalos • Metal Enrichment

  18. Complex Reionization:Metal Enrichment Reionization • Ejection by supernova winds is most likely mechanism • Regulates transition from Pop III (massive?) star formation to Pop II • Complex and extended • Highly inhomogeneous • New galaxies form Pop III stars, even late (?) • Extended  no sharp features in reionization • Extremely uncertain timing and extent Increasing Wind Efficiency SF, AL (2005)

  19. Metal Absorption Lines SDSS collaboration (1+zs)lLya (1+zs)lmetal  Can probe lLya/lmetal< (1+z)/(1+zs) < 1

  20. Metal Absorption Lines • Important lines: • Most abundant elements produced by Type II SNe: C (YCSN=0.1 Msun), O (0.5 Msun), Si (0.06 Msun), Fe (0.07 Msun) • Most abundant elements produced by VMS SNe: C (YCSN=4.1 Msun), O (44 Msun), Si (16 Msun), Fe (6.4 Msun) • Ionization states determined by radiation background and nearby galaxy  CII, OI, SiII, FeII for neutral medium  CIV, SiIV for ionized medium

  21. Methodology • One wind bubble per halo • Star formation history from extended Press-Schechter • Mechanical Luminosity provided by SN rate (and hence SFR) • Use thin-shell approximation (Tegmark et al. 1993) • All mass confined to spherical thin shell (no fragmentation) • Sweeps up all IGM mass • Driving force is hot bubble interior • Consider low-ionization states in spherical shells • Free parameters: f*, ESN, IMF, fw (and others)

  22. Wind Characteristics: Shell Radius • Points: Monte Carlo model • Solid line: Halo virial radius • R ~ E1/3 (at constant mass) • R ~ M1/5 (at constant f*) SF, AL (2003)

  23. Wind Characteristics: OI Equivalent Width • Crosses: z=20 • Dashes: z=16 • Triangles: z=12 • Points: z=8 • W ~ M/R2 ~ M3/5 • Strongest absorbers surround largest galaxies SF, AL (2003)

  24. Absorption Statistics • Scalo IMF, f*=0.1 • OI l1302 is shown • One absorption line per wind (no fragmentation) • Wtot depends on f*, shape depends on fw • Q~(10-4,10-3,0.01,0.1) z=8 z=12 z=16 z=20 SF, AL (2003)

  25. What Can We Learn? • z=8,f*=0.1 • Net absorption similar for low, high-ionization states • Reveals enrichment patterns, ionizing background (+clumping) • Hot gas will remain invisible: OVI < Ly • Identifying lines may be a challenge • Doublets straightforward • Others require several lines together? • And distinguish from noise! SF, AL (2003)

  26. What Can We Learn? • Some models require “prompt enrichment” by VMS stars in minihalos: Q~0.1-1 at high redshifts • Expect significant absorption, e.g. CII: ~0.16 (Z/10-2.5 Zsun) (1+z/7)3/2 • Actually expect forest of features from density structure • Do background sources exist?

  27. Metal Lines and Reionization • OI/HI in tight charge-exchange equilibrium • ~0.14 (Z/10-2.5 Zsun) for equivalent GP trough • Dense regions enriched first but ionized last  “forest” of (unsaturated) OI lines near reionization • Stretch into near-IR: sky lines difficult! Oh (2002)

  28. Summary • SDSS quasars indicate something dramatic happens at z~6, but its nature unclear • Huge cosmic variance between two lines of sight! • Models of reionization suggest variations in  on large scales • Allows transmission in QSO spectra when xHI<0.25: study transition from “bubble-dominated” to “web-dominated” universe • Other probes of topology: 21 cm emission, kSZ effect, Ly galaxies • Metal lines with >Ly must appear beyond reionization! • Trace course of enrichment (crucial piece of extended reionization) • “OI forest” at tail end of reionization • Expectations far from clear: hugely simplified models so far!

  29. The Case Against anInterloper: Transmission Spikes • If emission lines from intervening galaxy, should be extended source (>1 arcsec) • White et al. (2005) observed with narrowband ACS filter: point source! • z=5 galaxy does help clear Ly forest

  30. SDSS Quasars: “Proximity Zones” • Ly/Ly flux ratios • J1030 has region with Ly transmission but no Ly • Requires smooth damping wing component  xHI>0.1? (Mesinger & Haiman 2004) • Does not appear in J1148 • QSO redshift + edge of transmission  measure size of HII region? • Luminosity + lifetime  xHI>0.1 (Wyithe & Loeb 2004) • But see Yu & Lu (2004) White et al. (2003)

  31. The Topology of Reionization • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 Ionized IGM Galaxy Neutral IGM

  32. The Topology of Reionization • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 Ionized IGM Galaxy Neutral IGM

  33. The Topology of Reionization • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 Ionized IGM? Galaxy Neutral IGM

  34. The Topology of Reionization • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 • Can construct an analog of Press-Schechter mass function = mass function of ionized regions Ionized IGM Galaxy Neutral IGM

  35. Bubble Sizes: Why? • Mostly independent of redshift at fixed xH • Depends primarily on the bias of ionizing sources • Solid lines: f*=const • Dashed lines: f*~m2/3 xH=0.25 xH=0.8 SF, MZ, LH (in prep)

  36. Metal Pollution: Filling Factor • Different curves show f*=0.01, 0.1, 0.5, from bottom to top • Solid: H2 cooling • Dotted: Atomic cooling • Ignores galaxy clustering! FL03

  37. What Can We Learn? • z=8 • Solid: f*=0.5, f*=0.1, f*=0.01 • Dashed: vary fraction of SN energy in wind FL03

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