Decoding Absorption in the IGM

1. Decoding Absorption in the IGM Precision measurement program with integrated observations and simulations 50+ large full hydrodynamic simulations of IGM publicly available Calibrated 1% measurements of mean flux 1.6 < z < 3.5 We find sets of parameter values that match Lya forest within errors

2. Publications David Tytler, David Kirkman, John M. O'Meara, Nao Suzuki, Adam Orin, Dan Lubin, Pascal Paschos, Tridivesh Jena, Wen-Ching Lin, Michael L. Norman University of California, San Diego Avery Meiksin University of Edinburgh Tytler et al 2004 ApJ 617, 1 astro-ph/0403688 Tytler et al 2004 AJ 128, 1058 astro-ph/0405051 Kirkman et al 2005 MNRAS in press 0504391 Jena et al 2005 MNRAS in press 0412557

3. H absorption is sensitive to many Parameters cosmological parameters: Ho, ΩΛΩm Ωb, Pk (n, σ8) astrophysical parameters: UVB photoionization heating (UVB spectrum) We need to adjust all of these to fit the Lya Forest. If we know all but one, can find that one, if priors well known potentially small error, competitive with best current

4. Mean Flux 1: Lick Kast Spectra 77 QSOs First calibrated measurement. Fit continua to realistic artificial spectra with known mean flux. Prior measurements were significantly less accurate: -the main error in measurement of the matter power spectrum.

5. Mean Flux 2: We use HIRES at z 2.2 – 3.5 Sigma of continuum fit error per 121Ang is 1.2%. Mean error for 275 such segments is +0.29% HIRES flux calibrated with 2 fits One of 4 artificial, realistic emission lines and errors 1070-1170 rest

6. Emission lines everywhere Suzuki ApJ in press astro-ph/0503248

7. Emission Lines Sometimes Strong In low S/N they are hard to see. You might place continuum too low and systematically underestimate the amount of absorption

8. Measured Mean Ly-alpha Absorption Spectra 77 QSOs z=2 from Lick Kast spectrograph Measured mean absorption from Ly-alpha in IGM. First calibrated measurement Tytler et al ApJ 617, 1, 2004

9. IGM only Absorption Removed mean metal lines and Lya from LLS from each point 24 QSOs HIRES 8 km/s 77 QSOs Lick 250 km/s

10. Detected LSS at 153 Mpc at z=1.9 Large Scale Structure makes 1/3 of the dispersion in mean absorption in 121 Angstrom segments: sigma(DA) = 3.5% Simulation, 76.8 Mpc box. Kast spectra, including metals and Lya of LLS

11. Absorption due to LyaF alone DA = Absorption = Fraction of flux absorbed in Lya Forest, no metals, no Lya of LLS Fbar(z=2)=0.873 Fbar(z=3)=0.719 0.0062(1+z)2.75 If DA(z) is smooth function, we have 1% error, mostly from metal subtraction

12. Mean Absorption blank Our new measurement give less absorption than prior work, and not just from the metal and LLS removal. This requires more ionizing photons

13. 50 large Hydrodynamic Simulations Cell size: 18, 37, 75, 150 kpc (comoving, h=0.71) Box size: 9, 19, 38, 77 Mpc (comoving) various: σ8, UVB intensity, heating from He II ionizations Available on web: astro-ph/0412557 Jena et al., or email log baryon density, z=2, from 1024 cube, 75 kpc cells

14. Controlling the Temperature We control temperature using X228 heat per HeII ionization, in HM III units The rate of HI and HeII ionization depends on intensity The heating per baryon depends on X228 We hope that X228 > 1 corrects for opacity missing because our simulations are optically thin. We find X228 = 1, the heating from the HM III spectrum shape, matches data.

15. Line Width constrains IGM Temperature Less heating, cooler gas: more narrow lines Line per unit z per km/s Line width b (km/s)

16. Mean line Width constrains IGM Temperature Simulation with T=14,300 K at mean density at z=2 σ8=0.9, n=1 fits Kim et al 286 lines Line per km/s log NHI 12.5 – 14.5 Ly-alpha Line width b (km/s)

17. Temperature-Density 14,300 K at mean density at z=2

18. Homogeneous Reionization Simulation: LCDM+HMIII Paschos & Norman (2004)

19. The UVB to Fit Lya Forest depends on σ8 HI, HeII photoionization rate (Haardt & Madau III = 1) Heating due to He II ionization (Haardt & Madau III = 1) Hotter move UV photons σ8 (n=1) σ8 (n=1)

20. Mean UVB Intensity We obtain sets of parameters h=0.71, ΩΛ = 0.73, Ωm = 0.27, Ωb =0.044, n=1.0, σ8 = 0.90 that agree with Lya forest data at z=2: line widths, mean flux, power spectrum when rate of photoionization of H by UVB is Gamma = 1.33 x 10-12 per HI atom per second or J=0.30 x 10-21 erg/cm2/s/Hz/sr. Error 30% (Bolton et al.) very close to HM III However, at z=3, we still need Gamma = 1.3 x 10-12 per HI atom per second about 1.3 times the HM III rate missing photons?

21. Three Baryon Density Measurement Agree Baryon density measured in 3 independent ways: IGM result requires priors for all main cosmological and astrophysical parameters. The error quoted is from 1% error in mean flux alone. External error much larger If equivalence of values holds up: SBBN applies: no extra relativistic particles constancy of the baryon and photon densities no missing baryons at z=2

22. Higher Accuracy Temperature To get more accurate temperature distribution we need radiative transfer of photons from the individual QSOs that we suspect reionized the HeII. We need huge simulations because they are rare. Paschos, Norman & Bordner used a 100 Mpc simulation that was optically thin in HI and HeI ionizing photons. They post-processed to include RT of HeII ionizing photons…but do not resolve LyaF. Adding RT to AMR

23. Late He II Reionization by QSOs Will be able to match HeII opacity & follow temperature evolution of IGM Z=5 Z=3 Z=2.6 Z=6 Z=3.2 Paschos, Norman & Bordner (2005) Z=2.6

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