Epoch of Reionization / 21cm simulations

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Epoch of Reionization / 21cm simulations

• Mário Santos
• CENTRA - IST

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21cm signal - simulation
Sky simulation (º 87 MHz)
Ionization fraction (º 87 MHz)

• Brightness temperature maps (21cm HI line)
• Post-processing with fast semi-numerical
  prescription to get spin temperature (Santos et
  al., 2008, ApJ, 689, 1)

• Dark matter / radiative transfer simulation 100
  Mpc/h side, (720)3 cells, 24 billion particles
  (Shin et al., 2007, ArXiv e-prints, 708)

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21cm signal - simulation
Sky simulation (º 87 MHz)
Ionization fraction (º 87 MHz)

• 21cm signal
• TS HI spin temperature depends on collisional
  coupling, Ly coupling, gas temperature (X-ray
  heating)

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21cm simulation Ly fluctuations
z20
mK

• Top left Sky simulation with homogeneous Ly
• Top right Sky simulation with Ly fluctuations
• Bottom - left power spectrum of the Ly photon
  flux
• Important for z 15
• Dominates over collisions up to z22

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21cm simulation X-ray fluctuations
z15
mK

• Top left sky simulation with homogeneous X-ray
  heating
• Top right sky simulation with fluctuations in
  the gas temperature due to X-rays
• Bottom left power spectrum of the gas
  temperature
• Important for z gt 10!

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EoR / 21cm sky simulation

• Brightness temperature maps
• Box size - 100 Mpc/h (50) (7 MHz)
• Box resolution - 139 Kpc/h (4) (10 KHz)
• 6 lt z lt 25 (55 MHz lt º lt 203 MHz)
• Available for SKADS use

Santos et al., 2008, ApJ, 689, 1
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21cm signal redshift evolution

• Average temperature
• Top Spin (dotted) gas (red dashed) CMB (solid)
• Bottom brightness temperature with all
  fluctuations (black) and without x-ray
  fluctuations (red)

• Power spectrum evolution
• Signal increases with redshift! (up to z 16)

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Power spectrum

• Expected range measured by SKA

• Expected range measured by 1st generation
  experiments (e.g. LOFAR)

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Power spectrum - errors

• Tsky 1215 K _at_ 100 MHz
• Bandwidth 8 MHz per redshift
• ttot1000 hours
• Blue (SKA type)
• Aeff4000 m2/K _at_ 100 MHz
• FoV 200 deg2
• Dmax5 Km (with 70 of Aeff)
• Dmin15 m
• Green (LOFAR type)
• 130 m2/K _at_ z6 (º203 MHz)
• FoV 18 deg2 (x2)
• Dmax1 Km (with 80 of Aeff)
• Dmin100m

• Red solid line brightness temperature 3-d power
  spectrum with all fluctuations included
• Dashed lines total error in the power spectrum
  bins0.5k

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Map making - 1
Signal Noise
Signal
T (mK)
z7, º177 MHz, º2 MHz, µ1 degree, µ35
z7, º177 MHz, µ1 degree, µ9
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Map making - 2
Signal
Signal Noise
T (mK)
Z9.2, º140 MHz, º2MHz, µ32, µ46
Z9.2, º140 MHz, µ32, µ4.8
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Map making - 3
Signal
Signal Noise
T (mK)
z12, º110 MHz, º2 MHz, µ32, µ0.94
z12, º110 MHz, µ32, µ4.8
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Note SKA Field of View

• Need larger simulations for proper testing of the
  observation pipeline
• Use semi-numerical dark matter simulation with
  analytical prescription for ionized bubbles (in
  preparation)
• Also good for fast power spectrum generation

200 degree2
50
Fast semi-numerical dark matter / ionized bubbles
simulation
21cm simulation
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Analytical models xi power spectrum

• Useful to quickly explore the full astrophysical
  and cosmological parameter space for 21cm
  surveys!
• Easy to probe both large and small scales
• Left power spectra of the ionization fraction
  (divided by the dark matter one)

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Analytical models 21cm power spectrum

• Power spectra of the 21cm brightness temperature
  for the simulation (black) versus one
  semi-analytical model
• OK for z lt 10 (e.g. first generation experiments)
• At z10 (SKA) X-ray and Ly fluctuations are
  important need further improvements

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What can we learn?

• Probe a crucial step in the evolution of the
  Universe - formation of first non-linear
  structures (first stars and galaxies)
• Complex Reionization history 6 lt z lt20 !
  (currently very little experimental data)
• Astrophysical parameters xi, Ly flux, gas
  temperature, star formation, photon escape
  fraction
• Cosmological parameters ?, ?mh2, ?bh2, ns,
  neutrino mass

Mao et al, PRD 78, 023529 (2008)
McQuinn et al, ApJ 653, 815 (2006)