Simulating Lyman-!Intensity Maps with

Radiative Transfer during Reionization

Eli Visbal (Flatiron Institute)Matthew McQuinn (University of Washington)

• 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

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

Lyman-! Radiative Transfer

• Previous work assumed Ly!emmission clustered as galaxies• Ignores complex

interactions with IGM• Developed Monte

Carlo RT code

50 Mpc

21cmFAST

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)

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)

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

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

Simulated Lyman-! Intensity MapsNeutral Fraction No IGM

Scattered Component Unscattered Component

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

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

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

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