The Twilight Zone of Reionization Steve Furlanetto Yale University March 13, 2006 Steve Furlanetto Yale University March 13, 2006 Collaborators: F. Briggs, L. Hernquist, A. Lidz, A. Loeb, M. McQuinn, S.P. Oh, J. Pritchard, A. Sokasian, O. Zahn, M. Zaldarriaga

Outline Reionization on a Global Level Assumptions Feedback Inhomogeneous Reionization Early Phases Late Phases Observational Prospects Reionization on a Global Level Assumptions Feedback Inhomogeneous Reionization Early Phases Late Phases Observational Prospects

Simple Reionization Models: Ingredients Source Term: Identify sources Assign f * Assign IMF Assign f esc Sink Term:  n e n H C Source Term: Identify sources Assign f * Assign IMF Assign f esc Sink Term:  n e n H C Sokasian et al. (2003)

Simple Reionization Models: Ingredients Source Term: Identify sources Assign f * Assign IMF Assign f esc Sink Term:  n e n H C Doesn’t fit WMAP+SDSS Source Term: Identify sources Assign f * Assign IMF Assign f esc Sink Term:  n e n H C Doesn’t fit WMAP+SDSS

Reionization Models: Feedback I Any or all parameters may evolve! Photoheating Metallicity H 2 cooling Feedback on clumping Double reionization difficult to arrange (SF, AL 2005) Any or all parameters may evolve! Photoheating Metallicity H 2 cooling Feedback on clumping Double reionization difficult to arrange (SF, AL 2005)

Reionization Models: Feedback II Pop III/Pop II transition IGM Enrichment Clustering ISM Enrichment Gradual? See Cen’s talk later on SF, AL (2005)

The Global 21 cm Signal SF (in prep) Pop II StarsPop III Stars

Inhomogeneous Reionization z= Mpc comoving  =0.1 MHz SF, AS, LH (2004)

z=16.1  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=14.5  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=13.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=12.1  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=11.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=10.4  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=9.8  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=9.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=8.7  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=8.3  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=7.9  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=7.5  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

z=9.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) Inhomogeneous Reionization

Photon Counting Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Neutral IGM Ionized IGM Galaxy

Photon Counting Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Neutral IGM Ionized IGM Galaxy

Photon Counting Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Neutral IGM Ionized IGM? Galaxy

Photon Counting Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Can construct an analog of Press-Schechter mass function = mass function of ionized regions Simple ansatz: m ion =  m gal  = f * f esc N  /b / (1+n rec ) Then condition for a region to be fully ionized is f coll >  -1 Can construct an analog of Press-Schechter mass function = mass function of ionized regions Neutral IGM Ionized IGM Galaxy

SF, MZ, LH (2004a)  =40 x H =0.96 x H =0.70 x H =0.25 Bubble Sizes Bubbles are BIG!!! Many times the size of each galaxy’s HII region 2 Mpc = 1 arcmin Much larger than simulation boxes Typical galaxy bubble

SF, MZ, LH (2004a)  =40 x H =0.96 x H =0.70 x H =0.25 Bubble Sizes Bubbles are BIG!!! Have characteristic size Scale at which typical density fluctuation is enough to ionize region Galaxy bias gives a boost!

The Characteristic Bubble Size Bubbles are BIG!!! Have characteristic size Depends primarily on the bias of ionizing sources Bubbles are BIG!!! Have characteristic size Depends primarily on the bias of ionizing sources x H =0.84 x H =0.025 SF, MM, LH (2005) x H =0.35

SF, MM, LH (2005) Bubbles: Redshift Dependence Bubbles are BIG!!! Have characteristic size Sizes independent of z (for a fixed x H ) x H =0.84 x H =0.025 x H =0.35

SF, MM, LH (2005) Bubbles Bubbles are BIG!!! Have characteristic size Sizes independent of z (for a fixed x H ) It works! See McQuinn talk and poster x H =0.84 x H =0.025 x H =0.35

SF, MM, LH (2005) A Curious Result… FZH04 bubbles grow to be infinitely large! What do we mean by a “bubble”? Full extent of ionized gas? (Wyithe & Loeb 2004) Mean free path of ionizing photon? (SF, SPO 2005) x H =0.84 x H =0.025 x H =0.35

Much Ado About Clumping For bubble to grow, ionizing photons must reach bubble wall Neutral IGM Ionized IGM

Much Ado About Clumping Mean free path must exceed R bub  larger bubbles must ionize blobs more deeply Neutral IGM Ionized IGM

Much Ado About Clumping Outskirts of blobs contain densest ionized gas  recombination rate increases with mean free path Neutral IGM Ionized IGM

Much Ado About Clumping Growing bubble thus requires ion rate > recombination rate (see also Miralda- Escude et al. 2000) Clumping factor is model-dependent!!! Neutral IGM Ionized IGM

SF, SPO (2005) x H =0.49 x H =0.32 x H =0.08 Bubbles and Recombinations Recombinations impose saturation radius R max R max limit depends on… Density structure of IGM Emissivity (rate of collapse) x H =0.16

Overlap and Phase Transitions In simulations, reionization appears to be an extremely rapid global phase transition Gnedin (2000)

The Hidden Meaning of Overlap Gnedin (2000) Box Size SF, SPO (2005) R max Without recombinations

Fuzzy Overlap For any point, overlap is complete when bubble growth saturates Gives reionization an intrinsic width!!! Constrains density structure Quasars show  z~0.3 SF, SPO (2005)

Much Ado About Clumping Assuming uniform ionizing flux: C>30 (Gnedin & Ostriker 1997) Assuming voids ionized first: thin lines (MHR00) Assuming uniform ionizing flux: C>30 (Gnedin & Ostriker 1997) Assuming voids ionized first: thin lines (MHR00) SF, SPO (2005)

Much Ado About Clumping Assuming ionizing sources are clustered: thick lines Spatially variable Depends on P(  ) AND bubble model!!! Assuming ionizing sources are clustered: thick lines Spatially variable Depends on P(  ) AND bubble model!!! SF, SPO (2005)

Reionization Observables The 21 cm Sky CMB Temperature Anisotropies Ly  Emitters Quasar (or GRB) Spectra The 21 cm Sky CMB Temperature Anisotropies Ly  Emitters Quasar (or GRB) Spectra

The 21 cm Power Spectrum Model allows us to compute statistical properties of signal Rich set of information from bubble distribution (timing, feedback, sources, etc.) Full 3D dataset Model allows us to compute statistical properties of signal Rich set of information from bubble distribution (timing, feedback, sources, etc.) Full 3D dataset x i =0.78 z=10 x i =0.13 x i =0.36 x i =0.48 x i =0.59 x i =0.69

Ly  Emitters and HII Regions Total optical depth in Ly  transition: Damping wings are strong See many later talks! Total optical depth in Ly  transition: Damping wings are strong See many later talks! IGM HI

Clustering on Large Scales Large scales: Galaxies in separate bubbles  depends on clustering of bubbles Large bubbles are rare density peaks: highly clustered

Clustering on Large Scales Large scales: Galaxies in separate bubbles  depends on clustering of bubbles Large bubbles are rare density peaks: highly clustered

Clustering on Small Scales Nearly randomly distributed galaxy population Small bubble: too much extinction, disappears Large bubble: galaxies visible to survey Nearly randomly distributed galaxy population Small bubble: too much extinction, disappears Large bubble: galaxies visible to survey

Clustering on Small Scales Small bubble: too much extinction, disappears Large bubble: galaxies visible to survey Absorption selects large bubbles, which tend to surround clumps of galaxies Small bubble: too much extinction, disappears Large bubble: galaxies visible to survey Absorption selects large bubbles, which tend to surround clumps of galaxies

Clustering on Small Scales Small bubble: too much extinction, disappears Large bubble: galaxies visible to survey Absorption selects large bubbles, which tend to surround clumps of galaxies Small bubble: too much extinction, disappears Large bubble: galaxies visible to survey Absorption selects large bubbles, which tend to surround clumps of galaxies

The Evolving Correlation Function Top panel: Small scale bias b sm Middle panel: Large scale bias b(infinity) Bottom panel: Ratio of the two Crossover scale is R char SF, MZ, LH (2005)

Secondary CMB Anisotropies Nonlinear kinetic Sunyaev-Zeldovich and “Patchy Reionization” signals Especially large for extended reionization Nonlinear kinetic Sunyaev-Zeldovich and “Patchy Reionization” signals Especially large for extended reionization McQuinn et al. (2005) Total Patchy

Quasar Spectra SDSS J1030 (z=6.28) No flux for z= SDSS J1148 (z=6.42) Residual Flux! (White et al. 2005, Oh & Furlanetto 2005) A signature of reionization? (Wyithe & Loeb 2005, Fan et al. 2006) White et al. (2003)

Quasar Spectra But complications! Aliasing (Kaiser & Peacock 1991) But complications! Aliasing (Kaiser & Peacock 1991) High-k mode Line of sight

Quasar Spectra But complications! Aliasing (Kaiser & Peacock 1991) Transmission bias because only see through rare voids But complications! Aliasing (Kaiser & Peacock 1991) Transmission bias because only see through rare voids

Quasar Spectra Observed variance slightly more than expected from uniform ionizing background Structure in intrinsic quasar spectra is likely another significant contributor Difficult but possible! Observed variance slightly more than expected from uniform ionizing background Structure in intrinsic quasar spectra is likely another significant contributor Difficult but possible! Lidz, Oh, & Furlanetto (2006) Smoothing length=40 Mpc/h

Conclusions Models of global reionization history subject to uncertainties about parameters Feedback especially difficult! Inhomogeneous Reionization Early phases: photon counting Late phases: recombinations A number of observational opportunities ahead! Models of global reionization history subject to uncertainties about parameters Feedback especially difficult! Inhomogeneous Reionization Early phases: photon counting Late phases: recombinations A number of observational opportunities ahead!