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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
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.
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.
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.
• 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!