Cosmology with GRBs. Giancarlo Ghirlanda. - Osservatorio di Brera.

Transcription

1 Cosmology with GRBs - Osservatorio di Brera Giancarlo Ghirlanda In coll. with Gabriele Ghisellini Davide Lazzati Claudio Firmani Vladimir Avila-Reese

2 GRBs are fast transient high energy cosmological distances Prompt emission Afterglow emission energies > 10 kev 1 ms to 1 ks high varibility energies X, days to months X, Opt,, IR, Radio smooth powerlaw(s)

3 The standard picture Γ = Γ = 10

4 GRBs are cosmological Gamma ray position accuracy 2 deg!! Need arcmin accuracy to 1. Identify the counterpart 2. Follow the afterglow and measure the redshift GRB X ray afterglow indetification Optical transient OT spectrum 42 redshifts /3000 GRBs

5 GRB typical Fluence (i.e. time int. flux) is erg/cm 2 42 GRBs with redshift Assuming isotropy Huge isotropic equivalent energy!!

6 Jet effect Γ, Surf. Relativistc beaming: emitting surface 1/Γ Jet opening angle Log(F) Jet Break ϑ 1/Γ Log(t)

7 GRB Jet measure Jet break Jet break time t break Jet opening angle ϑ

8 True energetics Isotropic equivalent energy Frail et al E true = E iso (1 cos ϑ) Bloom et al. 2003

9 Prompt emission spectrum GRB Spectrum GRB Peak Energy Characteristic energy of most emitted photons

10 28 GRB +2 XRF Amati et al. 2002, Ghirlanda et al. 2004? 1-cos( cos(θ) t 3/ jet,d (η γ n) 1/8 θ= /8 1/8 (1+z) γ,iso,52 uniform n, 1<n<10 if unknown 1 kev 10 MeV η γ =0.2 (1+z) E γ, E p (1+z)=E iso Isotropic energy [erg] 0.4 iso

11 Ghirlanda, Ghisellini & Lazzati 2004 E peak E true correlation χ 2 r =1.27 peak=k E Epeak =k E γ 0.706

12 Ghirlanda, Ghisellini & Lazzati 2004

13 Similar to Supernovae Ia Stretching : the slower the brighter

14 Luminosity distance Luminosity distance Ghirlanda, Ghisellini, Lazzati & Firmani 2004 E=10 51 erg redshift redshift

15 χ r 2 =1.32 χ r 2 =2.9

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18 15 GRB+SN 156 Consistent with WMAP: Ω =0.3, M Ω Λ =0.7 Ghirlanda, Ghisellini, Lazzati & Firmani 2004

19 Firmani, Ghisellini, Ghirlanda & Avila-Reese, 2004 P=w 0 ρc 2 transition z: a = 0 Flat Universe: Ω tot =1

20 Firmani, Ghisellini, Ghirlanda & Avila-Reese, 2004 P=(w 0 +w z) z)ρc 2 Flat Universe: Ω tot =1, Ω M =0.27

21 Swift Swift Firmani, Ghisellini, Ghirlanda,& Avila-Reese, 2004

22 In the Swift era: Fluences not strongly dependent on z Early afterglow very well monitored Hope for small errors even at high-z XRF XRF

23 Simulation for 150 Swift bursts 150

24 the latest GRB t break =0.3d

25 Updated Correlation Updated cosmological constraints `

26 Typical Afterglow High redshift GRBs and t break F t -1 for t<t break F t -2 for t>t z=1 t break = 2 days H 1 day Z=1 Z=10 t break =2 days VLT t break =11 days ELT ELT is mandatory to measure the jet break time of high z GRBs

27 Cosmology with high z GRBs 15 GRBs (present sample) 0.1 < z < GRBs 9 < z < 10

28 Conclusions GRBs are among the most powerful sources of the universe and through the GGL04 correlation can be used as cosmological rulers. GRBs (detectable out to z=17) represent the link between SN Ia and CMB primary anysotropies,, and allows to study the Universe geometry and dynamics. Requirements: accurate measure of t break + inclusion of very high redshift GRBs.. At z > 6-76 need for Extramely Large Telescopes. ELT high res. Imaging can also contribute in understanding the GRB progenitor nature, emission process nature, GRB dynamics ELT high res. Spectroscopy can contribute in understanding the GRB environs, galaxy population.

29 041006

30 wind

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32 Ghirlanda, Ghisellini, Lazzati & Firmani 2004

33 Spheres or jets? Jet break The fireball decelerates 1/Γ opens up

34 Eiso - E true tbreak measures θjet θ jet E true = Eiso (1-cos cosθjet )

35 Structured jets? θ jet E(θ)=const E(θ)=E 0 θ -2 θ view

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37 smooth bumpy

38 L Firmani et al. 2004

39 Universal Epeak? ~200 kev, observer frame Preece et al. BATSE

40 HETE II

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44 2 Ω M z=1 0 0 Ω Λ 2 d L

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47 The cosmic whirl

48 t break θ