Mário Santos1 EoR / 21cm simulations 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Epoch of...

Mário Santos 1EoR / 21cm simulations4th SKADS Workshop, Lisbon, 2-3 October 2008

Epoch of Reionization / 21cm Epoch of Reionization / 21cm simulationssimulations

Mário Santos

CENTRA - IST


21cm signal - simulation21cm signal - simulation

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

• Brightness temperature maps (21cm HI line)

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

Ionization fraction (º = 87 MHz) Sky simulation (º = 87 MHz)


21cm signal - simulation21cm signal - simulation

Ionization fraction (º = 87 MHz) Sky simulation (º = 87 MHz)

• 21cm signal:

• TS: HI spin temperature – depends on collisional coupling, Ly® coupling, gas temperature (X-ray heating)


21cm simulation – Ly21cm simulation – Ly®® fluctuations fluctuations

• 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 z=22

z=20mK


21cm simulation – X-ray fluctuations21cm simulation – X-ray fluctuations

• 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 > 10!

mKz=15


EoR / 21cm sky simulationEoR / 21cm sky simulation

• Brightness temperature maps:

• Box size - 100 Mpc/h (50’) (7 MHz)

• Box resolution - 139 Kpc/h (4’’) (10 KHz)

• 6 < z < 25 (55 MHz < º < 203 MHz)

• Available for SKADS use

Santos et al., 2008, ApJ, 689, 1


21cm signal – redshift evolution21cm 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)


Power spectrumPower spectrum

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

• Expected range measured by SKA


Power spectrum - errorsPower spectrum - errors

• Tsky ~ 1215 K @ 100 MHz

• Bandwidth ~ 8 MHz per redshift

• ttot=1000 hours

• Blue (SKA type):

• Aeff=4000 m2/K @ 100 MHz

• FoV ~ 200 deg2

• Dmax=5 Km (with 70% of Aeff)

• Dmin=15 m

• Green (LOFAR type):

• 130 m2/K @ z=6 (º=203 MHz)

• FoV ~18 deg2 (x2)

• Dmax=1 Km (with 80% of Aeff)

• Dmin=100m

• Red solid line: brightness temperature 3-d power spectrum with all fluctuations included

• Dashed lines: total error in the power spectrum; bins=0.5k


Map making - 1Map making - 1

z=7, z=7, ºº=177 MHz, =177 MHz, µµ=1 degree, =1 degree, ¢µ¢µ=9’’=9’’ z=7, z=7, ºº=177 MHz, =177 MHz, ¢º¢º=2 MHz, =2 MHz, µµ=1 degree, =1 degree, ¢µ¢µ=35’’=35’’

Signal + NoiseSignal + NoiseSignalSignal

T (m

K)

T (m

K)



Z=9.2, Z=9.2, ºº=140 MHz, =140 MHz, µµ=32’, =32’, ¢µ¢µ=4.8’’=4.8’’ Z=9.2, Z=9.2, ºº=140 MHz, =140 MHz, ¢º¢º=2MHz, =2MHz, µµ=32’, =32’, ¢µ¢µ=46’’=46’’

T (m

K)

T (m

K)

SignalSignal Signal + NoiseSignal + Noise



z=12, z=12, ºº=110 MHz, =110 MHz, µµ=32’, =32’, ¢µ¢µ=4.8’’=4.8’’ z=12, z=12, ºº=110 MHz, =110 MHz, ¢º¢º=2 MHz=2 MHz, , µµ=32’, =32’, ¢µ¢µ=0.94’=0.94’

SignalSignal Signal + NoiseSignal + Noise

T (m

K)

T (m

K)


Note: SKA Field of ViewNote: 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-Fast semi-numerical dark numerical dark matter / ionized matter / ionized bubbles simulationbubbles simulation

21cm simulation


Analytical models – xAnalytical models – xii power power

spectrumspectrum

• 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)


Analytical models – 21cm power Analytical models – 21cm power spectrumspectrum

• Power spectra of the 21cm brightness temperature for the simulation (black) versus one semi-analytical model

• OK for z < 10 (e.g. first generation experiments)

• At z&10 (SKA…) X-ray and Ly® fluctuations are important – need further improvements


What can we learn?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 < z <20 ! (currently very little experimental data)

• Astrophysical parameters: xi, Ly® flux, gas temperature, star formation, photon escape fraction…

• Cosmological parameters: ¤, mh2, bh2, ns, neutrino mass…

M.G. Santos and A. Cooray, Phys.Rev. D74 (2006) 083517

Mao et al, PRD 78, 023529 (2008)

McQuinn et al, ApJ 653, 815 (2006)

Mário Santos1 EoR / 21cm simulations 4 th SKADS Workshop, Lisbon, 2-3 October 2008 Epoch of...

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