UV Radiative Feedback During Reionization

UV radiative feedbackUV radiative feedback Ringberg, Germany 24-27. march, 2009Ringberg, Germany 24-27. march, 2009

UV Radiative Feedback During UV Radiative Feedback During ReionizationReionization

Andrei MesingerAndrei MesingerPrinceton UniversityPrinceton University


Current Reionization Constraints at z~6-7Current Reionization Constraints at z~6-7

• WMAP e ~ 0.0870.017 reionization z~11?

Dunkely+2009

Caution:

- integrated measurement

• Ly forest in GP troughs of SDSS QSOs

Fan et al. 2006: xHI ≥ 10-3 and accelerated evolution

Becker et al. 2007: no accelerated evolution

-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

• 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

-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)


Current Reionization Constraints at z~6-7, Current Reionization Constraints at z~6-7, contcont..

• No evolution in Ly emitter (LAE) LFIn isolation: xHI < 0.3 (e.g. Malhotra & Rhoads 2004)

Clustered: xHI < 0.5 (Furlanetto et al. 2006)

• Some evolution in LAE LF (Kashikawa et al. 2006)

• LAE clustering xHI < 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. 2008 disagree with impact on clustering

• Lack of Ly damping wing in z=6.3 GRB

Totani et al. 2006 xHI < 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) 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)


Challenges in Modeling Global ProcessesChallenges 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!


PhilosophyPhilosophyUse the right tool for the job!

one size DOES NOT fit all!

QuickTime™ and aH.264 decompressor

are needed to see this picture.

Mesinger (2007)


OutlineOutline

• Radiative feedback throughout reionization:– advanced stages of reionization and Mmin

– early stages (fossil HII regions around massive stars)


MMminmin in Advanced Stages of Reionization 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?


Systematic approach -> Minimize AssumptionsSystematic approach -> Minimize Assumptions

• 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)

Does UV radiative feedback impact the advanced stages of reionization? Does/How Mmin effectively increase in ionized regions?


Two Tier ApproachTwo Tier Approach• 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)

Mesinger & Dijkstra (2008)


Ionizing UV Flux FieldsIonizing UV Flux Fields


flux ∑ L(Mhalo)/r2 e-r/mfp


Global impactGlobal impact



MMminmin

• Factor of 10 increase in ionizing efficiency is required to extend suppression by only factor of 2 in mass.


Being Conservative…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


Relic HII RegionsRelic 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?

?

?


UV Radiative Feedback in Relic HII RegionsUV 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; O’Shea+2005; Abel+2007; ; Ahn & Shapiro 2007; Whalen+2008)

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)

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:

JJUVUV = 0 = 0 FlashFlash JJUVUV = 0.08 = 0.08 JJUV UV = 0.8= 0.8Then add LWB of various strengths


Pretty PicturesPretty Pictures

T(K)10 104

20 h

-1 k

pc

z = 25

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 24.9

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 24.62

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 24

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 23

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 22

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 21

JJUVUV = 0.08 = 0.08



T(K)10 104

20 h

-1 k

pc

z = 20

JJUVUV = 0.08 = 0.08


Physics OutlinePhysics 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!


Radial ProfilesRadial ProfilesJJUVUV = 0 = 0JJUV UV = 0.8= 0.8


Transient FeedbackTransient Feedback

_ FlashFlash JJUVUV = 0.08 = 0.08 JJUVUV = 0.8 = 0.8

Mesinger+ (2006) Mesinger+ (2008)


Physics Outline (halo embryos)Physics Outline (halo embryos)• 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 ok!


Eventual Positive FeedbackEventual Positive FeedbackJJUVUV = 0 = 0JJUV UV = 0.8= 0.8JJUVUV=0.8, J=0.8, JLWLW=10=10-3-3


ConclusionsConclusions

• 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!


Halo FilteringHalo FilteringMesinger & Furlanetto (2007)

z=8.7 N-body halo field fromMcQuinn et al. (2007)


Density FieldsDensity FieldsNumerical resultsfrom Trac+2008

z=7


Density Fields, cont.Density Fields, cont.Mesinger+ 2009 (in preparation)


HII Bubble FilteringHII Bubble FilteringMesinger & Furlanetto (2007)

RT ionization field fromZahn et al. (2007)


Cool PR MovieCool PR Movie

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are needed to see this picture.

DexM public release available at http://www.astro.princeton.edu/~mesinger

UV Radiative Feedback During Reionization

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