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Simulating Lyman-!Intensity Maps with
Radiative Transfer during Reionization
Eli Visbal (Flatiron Institute)Matthew McQuinn (University of Washington)
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• Large-scale 3D maps of galaxy line emission• 21cm, CO, CII, Lyman-!, HeII 1640Å• Measures cumulative emission from ALL sources
Figure Credit: Patrick Breysse
Galaxy Intensity Mapping
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Lyman-! Intensity Mapping During the Epoch of Reionization
• Doesn’t require metals• H recombination à
Lyman-! photons• Probe faint sources
during reionization
• Proposed instruments• SPHEREx• Cosmic Dawn Intensity
Mapper (CDIM)
Silva et al. 2012/2016, Pullen et al. 2014, Comaschi et al. 2016, Croft et al. 2016
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Lyman-! Radiative Transfer
• Previous work assumed Ly!emmission clustered as galaxies• Ignores complex
interactions with IGM• Developed Monte
Carlo RT code
50 Mpc
21cmFAST
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Lyman-! Radiative Transfer• Optical depth
very high near resonance• Ly! photons
random walk in space and frequency until far from line center
Fig.: Gronke et al. (2016)
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Monte Carlo Radiative Transfer
Optically Thick Sphere -- !=106
• Follow many MC photons• Generate random numbers at each scatter for
direction/frequency
• Many photons à representative frequency and observed spatial distribution
see Zheng & Miralda-Escude (2002), Dijkstra et al (2006), Faucher-Giguere et al. (2010)
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Lyman-! in HII Regions
• Idealized HII regions in expanding Universe• Large bubbles à photons highly redshifted before edge• Small bubble à photons scattered many times
1 Mpc
z = 10
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Simulated Lyman-! Intensity Maps
• Applied code to 21cmFAST simulations• Scattered component traces neutral IGM• Important new effect!• Probe of timing/topology of reionization
Visbal & McQuinn, in prep.50 Mpc
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Simulated Lyman-! Intensity MapsNeutral Fraction No IGM
Scattered Component Unscattered Component
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Simulated Lyman-! Intensity Maps
Frequency direction
Spat
ial d
irect
ion
Spat
ial d
irect
ion
Spatial direction
• Additional smearing in frequency direction• Scattered signal translated along frequency
direction due to redshift required for escape
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Power Spectrum
10-1 100 101
k[Mpc -1 ]
10-6
10-4
10-2
k3P L
ya(k
)/22 [
nW2
m-4
Sr-2
] no IGMscatteredunscatteredtotal
100 101
k[Mpc -1 ]
10-6
10-4
10-2
100
k3P L
ya(k
)/22 [
nW2
m-4
Sr-2
] no IGMscatteredunscatteredtotal
50% Neutral Fraction 72% Neutral Fraction
• Increased neutral fraction à increased “scattered component” ( 50% à 90% for fractions shown) • High neutral fraction à change in shape of power
spectrum• Contains information on reionization timing/topology
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Galaxy Cross-Correlation• Foreground H! lines
will make auto-correlation very challenging• Cross-correlation with
galaxies• Sensitivity estimate
• 72% neutral fraction• CDIM-like telescope• 10 deg2 survey, 105
second integration• 1000 brightest
galaxies• H! limited
10-1 100
k[Mpc -1 ]
10-4
10-3
k3P L
ya, G
al(k
)/22 [
nW m
-2 S
r-1]
scatteredunscatteredtotal1- sensitivity
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Conclusions
• Lyman-! IM is a promising probe of high-z Universe• Developed Monte Carlo RT code• Find strong component scattered by IGM• Contains information on reionization• Future work• Cross-correlations with galaxies, 21cm, CO maps, etc. • Mitigation of interloper H! emission• Reionization constraints• Add component from galaxy continuum