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Masayuki Umemura University of Tsukuba, Center for Computational Sciences

First Stars and GRBs, and their Cosmological Impacts. Masayuki Umemura University of Tsukuba, Center for Computational Sciences. Collaborators Susa, Suwa, Mori, Yajima, Nakamoto, Murakami, Yonetoku, Matsubayashi, Yamazaki , Hirose, Yonehara, Sato, Hosoda, Aoyama. Contents.

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Masayuki Umemura University of Tsukuba, Center for Computational Sciences

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  1. First Stars and GRBs, and their Cosmological Impacts Masayuki Umemura University of Tsukuba, Center for Computational Sciences Collaborators Susa, Suwa, Mori, Yajima, Nakamoto, Murakami, Yonetoku, Matsubayashi, Yamazaki , Hirose, Yonehara, Sato, Hosoda, Aoyama

  2. Contents Part I - Reionization by Pop III Stars Part II - Indicators for Ancient GRBs

  3. Part I - Reionization by Pop III Stars Degeneracy - Star formation rate in high-z objects - Escape fraction of ionizing photons

  4. Amati -Yonetoku Relation (Ep‐Eiso,Lp) Ep‐Lp relation Ep‐Eiso relation Amati et al. 2002, A&A, 390, 81 Amati 2006, MNRAS, 372, 233 Yonetoku et al. 2004, ApJ, 609, 935 Ep(1+z)∝ (Eiso)a, a=0.49+0.06-0.05 L52 = 4.29×10-5 [ Ep (1+z) ]1.94

  5. Pop III SFR derived from GRB Events Murakami, Yonetoku, MU, Matsubayashi, Yamazaki 2005, ApJ, 625, L13 689 GRBs Ep-Luminosity relation

  6. Reionization criterion fesc>3-10% at z=10 from GRB event rate escape fraction inhomogeneous IGM reionization homogeneous IGM reionization

  7. Reionization with GRB-derived SFR Wyithe et al, 2010, MNRAS, 401, 2561 Semi-analytic model + Ly forest + WMAP 5 year fesc=3-6% (68% confidence)

  8. Simulations of Reionization by Pop III Stars Cen 2003; Ciardi, Ferrara & White 2003;Somerville & Livio 2003; Fukugita & Kawasaki 2003; Wyithe & Loeb 2003; Sokasian et al. 2004; Ricotti & Ostriker 2004 Sokasian et al. 2004, MNRAS, 350, 47 1 Pop III star per halo of 106M, fesc=1 WMAP 1st year te=0.17±0.04 (Spergel+03) WMAP Five year te=0.084±0.016 (Komatsu+09)

  9. What is the Mass & Number of First Objects ? Yoshida et al. 2003, ApJ, 592, 645  CDM context (Yoshida et al. 2003; O’Shea & Norman 2007) MMJ M<MJ M>MJ Jeans instability through H2 cooling runaway Mhalo,cr  7105 M Mb,cr  105 M 6h-1Mpc mass resolution mb =30M

  10. Collapse of First Objects P3M-GRAPE-SPH SimulationsSuwa, MU, Susa WMAP CDM cosmology z=30 zin=1200, 60kpc [comoving]3 Baryon mass: 2106M Dark matter mass: 1107M z=20 3 x 108 particles for baryon + dark matter Maximum mass resolution: 0.07M in DM 0.014M in baryon No change of mass resolution throughout the simulation z=16

  11. z=50 z=40 z=30 Formation of First Stars Resolution Low (Suwa, MU, Susa 2010) P3M SPH Simualtion low resolution 106particles mb=2.94M high resolution 107particles mb=0.367M ultra high resolution 108particles mb=0.046M High

  12. Growth of Dark Matter Cusps low resolution high resolution ultra high resolution N=5×105 mDM=38M N=4×106mDM=4.8M N=3×107mDM=0.6M z=16 M(r)   r -1.5 baryon Jeans mass dark matter r (kpc) 1pc 1pc 1pc Collapse driven by dark matter cusps. Minimm mass Mb,min103M

  13. Dark matter cusps can reduce the minimum mass of • firsts objects from Mb,min105M down to 103M. • (Direct collapse to first stars) • The number of first stars could be larger by more than • an order of magnitude than previous prediction. fesc a few %

  14. Escape Fraction from Primordial Galaxies Yajima, MU, Mori, Nakamoto, 2009, MNRAS, 398, 715 3D Radiative Transfer Calaculation LAE phase LBG phase gas dust stars HI

  15. Escape Fraction of Ionizing Photons fesc=0.07–0.47 in LAE phase fesc=0.06–0.17 in LBG phase LAE phase LBG phase Escape fraction in Pop III objects could be significantly smaller than that in LAEs.

  16. Part II - Indicators for First GRBs • Microlensing of GRBs by an intervening Pop III star • Damping of CMB by TeV- photons from GRBs

  17. Image 1 Image 2 Microlensing of GRBs by Pop III Stars Hirose, MU, Yonehara, Sato, 2006, ApJ, 650, 252 Image 1 Observer GRB Pop III Star Image2 Time delay： intrinsic light curve lensed light curve Photon number (Point mass) t

  18. Auto-correlation (=64msn) lensed light curve C( ) I(t) τlens τlens 1 t 0 τlens τ

  19. Test by Artificial Lensing 800 Intrinsic light curve Intrinsic light curve GRB 970508 (z=0.835) 700 600 500 lensed 110 120 130 140 150 160 170 Photon number/64ms 3000 Total 1st image 2000 2nd image 1000 500 Time (s) source redshift

  20. Autocorrelation of Artificially Lensed GRB Lightcurves

  21. Time delay t=1s Lens Mass PopIIImass zL10 50 10 100 1 + zL Lens Pop III should be at zlens>10, and therefore zGRB>zlens.

  22. Bump detection probability for Lensed GRBs

  23. SWIFT Data Analysis 111GRB lightcurves (GRB 050401 - GRB 091130B) Results 98/111GRBs show almost featureless autocorrelation (suggestive for GRB nature?) 3/111GRBs exhibit bumps in autocorrelation

  24. GRB 090423 @ z=8.2 Time resolution is not sufficient to analyze the autocorrelation !

  25. blue: Windowed Timing (WT) data red: Photon Counting (PC) data Light curve Autocorrelation Light curve Autocorrelation GRB 060105 GRB 080307 GRB 060607 GRB 080906 GRB 060729 GRB 080404

  26. GRB 070129 t(bump)=1.9s *I-band detection (I=20.60.04) *Dust scattered X-ray halo GRB 090424 t(bump)=2.4s z=0.544 GRB 090904A t(bump)=1.8s z=?

  27. On-the-Spot Collision of GRB TeV- with CMB Photons GRB fireball pair-production TeV- CMB photon Pair production cross section

  28. Model Total energy Fireball radius Energy spectrum (Aharonian et al. 2005, 2007) GRB redshift

  29. Damping of CMB by High-z GRBs Differential optical depth for pair production Optical depth at zGRB Damped CMB at zGRB Damped CMB at z=0 (Observation)

  30. Damping of CMB by High-z GRBs R=3×109 cm, Emax=30TeV νpeak=1.6×1011Hz : peak frequency of CMB at z=0 100% z=30 z=20 z=10 1% Damping factor νpeak frequency (Hz)

  31. R=3×109 cm, Emax=50TeV νpeak=1.6×1011Hz : peak frequency of CMB at z=0 100% z=30 z=20 z=10 Damping factor 1% νpeak frequency (Hz)

  32. SUMMARY • Part I - Reionization by Pop III Stars • is concordant with WMAP5 if the escape fraction is • a few %,which may be significantly smaller than LAEs. • Part II - Indicators for Ancient GRBs • Microlensing of GRBs by an intervening Pop III star • needs more data with high time resolution • Damping of CMB by TeV- photons in high-z GRBs • could be detected, if CMB is observed shortly after • GRB event.

  33. Thank you

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