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UV Radiative Feedback During Reionization
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  1. UV Radiative Feedback During Reionization Andrei Mesinger Princeton University Ringberg, Germany 24-27. march, 2009

  2. Current Reionization Constraints at z~6-7 Caution: • WMAP te ~ 0.0870.017 reionization z~11? Dunkely+2009 - integrated measurement • rise in does not directly translate to rise in xHI(Furlanetto & Mesinger 2009) • analytical density models • -differences sensitive to low  • -extrapolation sensitive to continuum fitting • Ly forest in GP troughs of SDSS QSOs Fan et al. 2006: xHI ≥ 10-3and accelerated evolution Becker et al. 2007: no accelerated evolution • extremely model-dependent • cannot directly read size or evolution of proximity region from spectra! (Mesinger+ 2004; Mesinger & Haiman 2004; Bolton & Haehnelt 2007ab; Maselli+ 2006, 2007) • Size of Proximity Region: xHI ≥ 0.1 Wyithe & Loeb 2004; Wyithe+ 2004 Combined w/ independent constraints on L and age (Mesinger & Haiman 2004) Evolution in size (Fan et al. 2006): xHI ~ 10-3 Ringberg, Germany 24-27. march, 2009

  3. Current Reionization Constraints at z~6-7, cont. Caution: • L <--> M unknown • very model dependent • drop due to density and halo evolution? (Dijkstra et al. 2007) • reionization signature should be a flat suppression (Furlanetto et al. 2006; McQuinn et al. 2007; Mesinger & Furlanetto 2008a) • Iliev et al. 2008 disagree with impact on clustering • No evolution in Ly emitter (LAE) LF In isolation:xHI < 0.3 (e.g. Malhotra & Rhoads 2004) Clustered:xHI < 0.5 (Furlanetto et al. 2006) • Some evolution inLAE LF (Kashikawa et al. 2006) • LAE clustering xHI < 0.5(McQuinn et al. 2007) • no statistical significance • (McQuinn et al. 2008; • Mesinger & Furlanetto 2008b) • Lack of Ly damping wing in z=6.3 GRB Totani et al. 2006xHI < 0.2 • Detection of Ly damping wing in QSOs Sharp decline in flux (Mesinger & Haiman 2004) xHI> 0.2 Modeling Ly forest in proximity region (Mesinger & Haiman 2007) xHI > 0.03 - 2 sightlines - patchy reionization likely degrades confidence contours (Mesinger & Furlanetto 2008b) Ringberg, Germany 24-27. march, 2009

  4. Challenges in Modeling Global Processes Virtually nothing is well-known at high-z --> enormous parameter space to explore Dynamic range required is enormous: single star --> Universe Be systematic! Ringberg, Germany 24-27. march, 2009

  5. Philosophy Use the right tool for the job! Mesinger (2007) one size DOES NOT fit all! Ringberg, Germany 24-27. march, 2009

  6. Outline • Radiative feedback throughout reionization: • advanced stages of reionization and Mmin • early stages (fossil HII regions around massive stars) Ringberg, Germany 24-27. march, 2009

  7. Mmin in Advanced Stages of Reionization • Ionizing UVB suppresses gas content of low-mass galaxies(e.g. Efstathiou 1992; Shapiro+1994; Thoul & Weinberg 1996; Hui & Gnedin 1997; Gnedin 2000) • How important is this negative feedback during reionization? (we focus on atomically-cooled halos, Tvir>104 K) • can extend reionization • early work, z=2 halos with vcir<35km/s completely suppressed; vcir < 100km/s partially suppressed • NOT THIS SIMPLE! Not instantaneous; high-z mediated by more compact profiles, increased cooling efficiencies, shorter exposure times (Kitayama & Ikeuchi 2000; Dijkstra+ 2004) • Can we draw any general conclusions about this exceedingly complex problem? Ringberg, Germany 24-27. march, 2009

  8. Systematic approach -> Minimize Assumptions Does UV radiative feedback impact the advanced stages of reionization? Does/How Mmin effectively increase in ionized regions? • We do NOT attempt to self-consistently model reionization • LARGE parameter space (small knowledge at high-z): • z = 7, 10, 13 • <xHI> • ionization efficiency, fid (=1 to match z=6 LAE and LBG LFs) Ringberg, Germany 24-27. march, 2009

  9. Two Tier Approach Mesinger & Dijkstra (2008) • 1D hydro simulations to model collapse of gas + dark matter under UVB: fg(Mhalo, z, J21, zon=14) • Semi-numerical code (DexM) to model halo, ionization and inhomogeneous flux fields: J21(x, z, <xH>, fid) Ringberg, Germany 24-27. march, 2009

  10. Ionizing UV Flux Fields Mesinger & Dijkstra (2008) flux ∑ L(Mhalo)/r2 e-r/mfp Ringberg, Germany 24-27. march, 2009

  11. Global impact Mesinger & Dijkstra (2008) Ringberg, Germany 24-27. march, 2009

  12. Mmin • Factor of 10 increase in ionizing efficiency is required to extend suppression by only factor of 2 in mass. Ringberg, Germany 24-27. march, 2009

  13. Being Conservative… • No self-shielding • mfp = 20 Mpc (the high-end of z<4 LLS extrapolations; Storrie-Lombardi+ 1994) • zon = 14 (zre = 11.0 +/- 1.4; Dunkley+ 2008) • biased halo formation • No redshift evolution of J21 over zon --> z Ringberg, Germany 24-27. march, 2009

  14. Relic HII Regions • Short lived, massive Pop III stars carve out ionized bubbles, then turn off. • Structure formation is highly biased at high-z; what happens inside these relic HII regions? ? ? Ringberg, Germany 24-27. march, 2009

  15. UV Radiative Feedback in Relic HII Regions • Radiative feedback on subsequent star formation can be: • positive (e- catalyzes H2 formation/cooling channel) • negative (LW radiation disassociates H2; radiative heating can photoevaporate small halos or leave gas with tenacious excess entropy) Problem is very complex and can benefit from both semi-analytic (e.g. Haiman et al. 1996; Oh & Haiman 2003; MacIntyre et al. 2005), and numerical studies (e.g. Machacek+2003; Ricotti+2002; Kuhlen & Madau 2005; O’Shea+2005; Abel+2007; ; Ahn & Shapiro 2007; Whalen+2008) We attempt to quantify the feedback effects from a UVB consistent with that expected from an early Pop III star using the cosmological AMR code, Enzo. Fiducial runs: JUV = 0 JUV = 0.08 JUV = 0.8 Flash Then add LWB of various strengths Ringberg, Germany 24-27. march, 2009

  16. Pretty Pictures JUV = 0.08 z = 25 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  17. Pretty Pictures JUV = 0.08 z = 24.9 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  18. Pretty Pictures JUV = 0.08 z = 24.62 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  19. Pretty Pictures JUV = 0.08 z = 24 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  20. Pretty Pictures JUV = 0.08 z = 23 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  21. Pretty Pictures JUV = 0.08 z = 22 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  22. Pretty Pictures JUV = 0.08 z = 21 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  23. Pretty Pictures JUV = 0.08 z = 20 20 h-1 kpc 10 104 T(K) Ringberg, Germany 24-27. march, 2009

  24. Physics Outline • When the UVB turns on, gas gets ionized and heated to T~104 K. • The temperature increase sets-off an outward moving pressure shock in the cores of halos, where density profiles have already steepened. • This pressure shock smoothes out the gas distribution and leads to a decrease in gas density in the cores of halos. • Once the UVB is turned off, the gas rapidly cools to T~103 K through a combination of atomic, molecular hydrogen and Compton cooling. This temperature approximately corresponds to the gas temperature at the virial radius of such a proto-galactic, molecularly-cooled halo, thus effectively neutralizing the impact of temperature change on feedback. • A large amount of molecular hydrogen is produced, xH2 ~ few x 10-3, irrespective of the gas density and temperature. • The pressure-shock begins to dissipate and gas with a newly enhanced H2 abundance starts falling back onto the partially evacuated halo. • The enhanced H2 abundance allows the infalling gas to cool faster. - No RT! + Ringberg, Germany 24-27. march, 2009

  25. Radial Profiles JUV = 0.8 JUV = 0 Ringberg, Germany 24-27. march, 2009

  26. Transient Feedback _ Flash JUV = 0.08 JUV = 0.8 Mesinger+ (2006) Mesinger+ (2008) Ringberg, Germany 24-27. march, 2009

  27. Physics Outline (halo embryos) No RT ok! • When the UVB turns on, gas gets ionized and heated to T~104 K. • The temperature increase sets-off an outward moving pressure shock in the cores of halos, where density profiles have already steepened. • This pressure shock smoothes out the gas distribution and leads to a decrease in gas density in the cores of halos. • Once the UVB is turned off, the gas rapidly cools to T~103 K through a combination of atomic, molecular hydrogen and Compton cooling. This temperature approximately corresponds to the gas temperature at the virial radius of such a proto-galactic, molecularly-cooled halo, thus effectively neutralizing the impact of temperature change on feedback. • A large amount of molecular hydrogen is produced, xH2 ~ few x 10-3, irrespective of the gas density and temperature. • The pressure-shock begins to dissipate and gas with a newly enhanced H2 abundance starts falling back onto the partially evacuated halo. • The enhanced H2 abundance allows the infalling gas to cool faster. - + Ringberg, Germany 24-27. march, 2009

  28. Eventual Positive Feedback JUV=0.8, JLW=10-3 JUV = 0.8 JUV = 0 Ringberg, Germany 24-27. march, 2009

  29. Conclusions • UV feedback on T>104 K halos NOT strong enough to notably affect bulk of reionization (requires factor of ~100 increase in ionizing efficiencies) • Likely Mmin ~ 108 Msun throughout most of reionization after minihalos no longer dominate • In early relic HII regions, feedback can be both + and -, but is transient; eventual + feedback is interesting, but can be suppressed with modest values of LWB • Natural timescale for significant part of reionization is the growth of the collapsed fraction in T>104 K halos, with small filling factor tail extending to higher z due to T<104 K halos, likely regulated by LWB??? Late stages maybe slowed down by photon sinks??? • Dynamic range is important in modeling reionization! Ringberg, Germany 24-27. march, 2009

  30. Halo Filtering Mesinger & Furlanetto (2007) z=8.7 N-body halo field from McQuinn et al. (2007) Ringberg, Germany 24-27. march, 2009

  31. Density Fields z=7 Numerical results from Trac+2008 Ringberg, Germany 24-27. march, 2009

  32. Density Fields, cont. Mesinger+ 2009 (in preparation) Ringberg, Germany 24-27. march, 2009

  33. HII Bubble Filtering Mesinger & Furlanetto (2007) RT ionization field from Zahn et al. (2007) Ringberg, Germany 24-27. march, 2009

  34. Cool PR Movie DexM public release available at http://www.astro.princeton.edu/~mesinger Ringberg, Germany 24-27. march, 2009