HeII reionization: observational implications

Transcription

1 HeII reionization: observational implications Michele Compostella (Argelander Institute, Bonn) Cristiano Porciani (AIfA, Bonn), Sebastiano Cantalupo (UCSC, Santa Cruz) Intergalactic Matters Heidelberg, June 18th 2014

2 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

3 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: Å (Vanden Berk et al. 2001) L Å (Telfer et al. 2002) Numerical Methods 3/15

4 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

5 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

6 New simulations of HeII reionization 6/15

7 100 Mpc/h Reionization history 7/15

8 100 Mpc/h Reionization history 8/15

9 100 Mpc/h Reionization increases the temperature 9/15

10 Reionization increases the temperature 10/15

11 HeII reionization ends at z~3 Mean evolution in the new simulations Old simulations Compostella et al. (in prep.) Side Slides 11/15

12 Large fluctuations between lines of sight 16th-84th percentile 2nd -98th percentile mean Δz=0.04, Compostella et al. (in prep.) 12/15

13 Transparent chunks at high redshift CL Transparent: chunk with eff HeII CL To exclude an AGN-driven reionization at the 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

14 Transparent and opaque chunks Transparent: chunk with eff HeII 3 Opaque: chunk with eff HeII /15

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