HeII reionization: observational implications Michele Compostella (Argelander Institute, Bonn) Cristiano Porciani (AIfA, Bonn), Sebastiano Cantalupo (UCSC, Santa Cruz) Intergalactic Matters Heidelberg, June 18th 2014
Numerical methods AMR hydrodynamical simulations (RAMSES, Teyssier 2002) with galaxy-only homogeneous UV background (rescaled Haardt & Madau 2012) 100 Mpc/h boxes 8 runs using 2 source models: 6 runs starting at z=5 2 additional runs from z=6 Radiative transfer (RADAMESH, Cantalupo & Porciani 2011) from AGNs using: periodic boundary conditions lifetime of 45 Myr 50 frequency bins (1-40 ryd) timestep of 1-5 Myr galaxy-only homogeneous UV background Distribution of Simulated spectra of the HeII Lyα forest with Δz = 0.04 Numerical Methods eff HeII Nature of transparent chunks at high z 2/15
Calibration of the sources at z=4 Dark matter haloes at z=4: data points and fit (dashed line) from Glikman et al. (2011) M halo 4 M 1450 M halo = 2.5 log 1 3 h M sun (Silk & Rees 1998; Wyithe & Loeb 2002) AGN population reproduces data by Glikman et al. (2011) 80 sources (out of ~2000 DM haloes) Spectral Energy Distribution: 1 1300 Å (Vanden Berk et al. 2001) L 2 1300 Å (Telfer et al. 2002) Numerical Methods 3/15
Evolution of the luminosity function Pure Luminosity Evolution (PLE): mean number of sources is constant during the run, but their luminosity evolves or Pure Density Evolution (PDE): luminosity of the sources is constant, but the mean number of sources in the volume evolves PLE (green) PDE (purple) HM2012 (red) Numerical Methods 4/15
Previous results Reionization is extended in time End of reionization is model independent Multiple sources are required to ionize a gas element Bimodal equation of state during HeII reionization Previous Results Large fluctuations between lines of sight Good agreement with observational data at low z BUT Steep increase at z>3 Cannot explain new measurements at high z Δz=0.04 from Compostella et al. (2013) 5/15
New simulations of HeII reionization 6/15
100 Mpc/h Reionization history 7/15
100 Mpc/h Reionization history 8/15
100 Mpc/h Reionization increases the temperature 9/15
Reionization increases the temperature 10/15
HeII reionization ends at z~3 Mean evolution in the new simulations Old simulations Compostella et al. (in prep.) Side Slides 11/15
Large fluctuations between lines of sight 16th-84th percentile 2nd -98th percentile mean Δz=0.04, Compostella et al. (in prep.) 12/15
Transparent chunks at high redshift 0.841 CL Transparent: chunk with eff HeII 3 0.977 CL To exclude an AGN-driven reionization at the 0.999 CL (3 Gaussian σ) we should have 11 transparent chunks out of 37 at z~3.4 Δz=0.04, Bins of δz=0.2. Compostella et al. (in prep.) 13/15
Transparent and opaque chunks Transparent: chunk with eff HeII 3 Opaque: chunk with eff HeII 100 14/15
Conclusions i. HeII reionization is patchy and extended in redshift (Δz > 1) ii. Small dependence on the AGN model iii. End of the reionization at z~3 iv. Normal equation of state with ΔT0 ~10,000 K eff v. Large fluctuations in the measured HeII between different lines of sight vi. Fluctuations in the temperature persist after HeII ionization is completed eff vii.transparent chunks with HeII 3 are associated with regions of high photoionization rate and low densities that ionized early viii.the AGN-driven scenario is in agreement with observations for z<3.3. Moderate tension with the data is present at higher z (at the 97.7% CL, 2 Gaussian σ). Additional lines of sight are required to rule out the model at higher confidence (27 more chunks to get to 3 σ) Conclusions 15/15