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

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Presentation on theme: "UV radiative feedbackRingberg, Germany 24-27. march, 2009 UV Radiative Feedback During Reionization Andrei Mesinger Princeton University."— Presentation transcript:

1 UV radiative feedbackRingberg, Germany march, 2009 UV Radiative Feedback During Reionization Andrei Mesinger Princeton University

2 UV radiative feedbackRingberg, Germany march, 2009 Current Reionization Constraints at z~6-7 WMAP e ~ reionization z~11? Dunkely+2009 Caution: - integrated measurement Ly forest in GP troughs of SDSS QSOs Fan et al. 2006: x HI and accelerated evolution Becker et al. 2007: no accelerated evolution -rise in does not directly translate to rise in x HI (Furlanetto & Mesinger 2009) -analytical density models -differences sensitive to low -extrapolation sensitive to continuum fitting Size of Proximity Region: x HI 0.1 Wyithe & Loeb 2004; Wyithe Combined w/ independent constraints on L and age (Mesinger & Haiman 2004) Evolution in size (Fan et al. 2006): x HI ~ 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)

3 UV radiative feedbackRingberg, Germany march, 2009 Current Reionization Constraints at z~6-7, cont. No evolution in Ly emitter (LAE) LF In isolation: x HI < 0.3 (e.g. Malhotra & Rhoads 2004) Clustered: x HI < 0.5 (Furlanetto et al. 2006) Some evolution in LAE LF (Kashikawa et al. 2006) LAE clustering x HI < 0.5 (McQuinn et al. 2007) 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 disagree with impact on clustering Lack of Ly damping wing in z=6.3 GRB Totani et al x HI < 0.2 -no statistical significance (McQuinn et al. 2008; Mesinger & Furlanetto 2008b) Detection of Ly damping wing in QSOs Sharp decline in flux (Mesinger & Haiman 2004) x HI > 0.2 Modeling Ly forest in proximity region (Mesinger & Haiman 2007) x HI > sightlines - patchy reionization likely degrades confidence contours (Mesinger & Furlanetto 2008b)

4 UV radiative feedbackRingberg, Germany march, 2009 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!

5 UV radiative feedbackRingberg, Germany march, 2009 Philosophy Use the right tool for the job! one size DOES NOT fit all! Mesinger (2007)

6 UV radiative feedbackRingberg, Germany march, 2009 Outline Radiative feedback throughout reionization: –advanced stages of reionization and M min –early stages (fossil HII regions around massive stars)

7 UV radiative feedbackRingberg, Germany march, 2009 M min 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, T vir >10 4 K ) –can extend reionization –early work, z=2 halos with v cir <35km/s completely suppressed; v cir < 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?

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

9 UV radiative feedbackRingberg, Germany march, 2009 Two Tier Approach 1D hydro simulations to model collapse of gas + dark matter under UVB: f g (M halo, z, J 21, z on =14) Semi-numerical code (DexM) to model halo, ionization and inhomogeneous flux fields: J 21 (x, z,, fid ) Mesinger & Dijkstra (2008)

10 UV radiative feedbackRingberg, Germany march, 2009 Ionizing UV Flux Fields Mesinger & Dijkstra (2008) flux L(M halo )/r 2 e -r/ mfp

11 UV radiative feedbackRingberg, Germany march, 2009 Global impact Mesinger & Dijkstra (2008)

12 UV radiative feedbackRingberg, Germany march, 2009 M min Factor of 10 increase in ionizing efficiency is required to extend suppression by only factor of 2 in mass.

13 UV radiative feedbackRingberg, Germany march, 2009 Being Conservative… No self-shielding mfp = 20 Mpc (the high-end of z<4 LLS extrapolations; Storrie-Lombardi ) z on = 14 (z re = /- 1.4; Dunkley ) –biased halo formation No redshift evolution of J 21 over z on --> z

14 UV radiative feedbackRingberg, Germany march, 2009 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? ? ?

15 UV radiative feedbackRingberg, Germany march, 2009 UV Radiative Feedback in Relic HII Regions 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; OShea+2005; Abel+2007; ; Ahn & Shapiro 2007; Whalen+2008) Radiative feedback on subsequent star formation can be: positive (e - catalyzes H 2 formation/cooling channel) negative (LW radiation disassociates H 2 ; radiative heating can photoevaporate small halos or leave gas with tenacious excess entropy) 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: J UV = 0 Flash J UV = 0.08 J UV = 0.8 Then add LWB of various strengths

16 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 25 J UV = 0.08

17 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 24.9 J UV = 0.08

18 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = J UV = 0.08

19 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 24 J UV = 0.08

20 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 23 J UV = 0.08

21 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 22 J UV = 0.08

22 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 21 J UV = 0.08

23 UV radiative feedbackRingberg, Germany march, 2009 Pretty Pictures T(K) h -1 kpc z = 20 J UV = 0.08

24 UV radiative feedbackRingberg, Germany march, 2009 Physics Outline When the UVB turns on, gas gets ionized and heated to T~10 4 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~10 3 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, x H2 ~ few x 10 -3, irrespective of the gas density and temperature. The pressure-shock begins to dissipate and gas with a newly enhanced H 2 abundance starts falling back onto the partially evacuated halo. The enhanced H 2 abundance allows the infalling gas to cool faster. - + No RT!

25 UV radiative feedbackRingberg, Germany march, 2009 Radial Profiles J UV = 0 J UV = 0.8

26 UV radiative feedbackRingberg, Germany march, 2009 Transient Feedback _ Flash J UV = 0.08 J UV = 0.8 Mesinger+ (2006)Mesinger+ (2008)

27 UV radiative feedbackRingberg, Germany march, 2009 Physics Outline (halo embryos) When the UVB turns on, gas gets ionized and heated to T~10 4 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~10 3 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, x H2 ~ few x 10 -3, irrespective of the gas density and temperature. The pressure-shock begins to dissipate and gas with a newly enhanced H 2 abundance starts falling back onto the partially evacuated halo. The enhanced H 2 abundance allows the infalling gas to cool faster. - + No RT ok!

28 UV radiative feedbackRingberg, Germany march, 2009 Eventual Positive Feedback J UV = 0 J UV = 0.8 J UV =0.8, J LW =10 -3

29 UV radiative feedbackRingberg, Germany march, 2009 Conclusions UV feedback on T>10 4 K halos NOT strong enough to notably affect bulk of reionization (requires factor of ~100 increase in ionizing efficiencies) Likely M min ~ 10 8 M sun 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>10 4 K halos, with small filling factor tail extending to higher z due to T<10 4 K halos, likely regulated by LWB??? Late stages maybe slowed down by photon sinks??? Dynamic range is important in modeling reionization!

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

31 UV radiative feedbackRingberg, Germany march, 2009 Density Fields Numerical results from Trac+2008 z=7

32 UV radiative feedbackRingberg, Germany march, 2009 Density Fields, cont. Mesinger (in preparation)

33 UV radiative feedbackRingberg, Germany march, 2009 HII Bubble Filtering Mesinger & Furlanetto (2007) RT ionization field from Zahn et al. (2007)

34 UV radiative feedbackRingberg, Germany march, 2009 Cool PR Movie DexM public release available at


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