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Can We Search for the First Stars Using GRBs?

Can We Search for the First Stars Using GRBs?. Susumu Inoue (Kyoto U.). - signature of Pop III stars - Pop III -> II transition. “A long-standing theoretical problem has been put to rest.”. “A long-standing problem has been put to rest.”. K. Omukai, apparently distinguished professor.

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Can We Search for the First Stars Using GRBs?

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  1. Can We Search for the First Stars Using GRBs? Susumu Inoue (Kyoto U.) - signature of Pop III stars - Pop III -> II transition “A long-standing theoretical problem has been put to rest.” “A long-standing problem has been put to rest.” K. Omukai, apparently distinguished professor To solve a scientific problem, experimental (observational) tests are necessary!

  2. z~100-10 =metal/dust-free, H2+HD-cooling Pop 3 first star epoch assume: no metal/dust, B field, CR, turbulence, DM heating need to be tested observationally! Pop 3.1 (1st generation) massive, high UV 1st BH -> 1st QSO 1st HII region -> IGM reionization 1st SN -> 1st metal/dust (+CR+B) Pop 3.2 (2nd generation) not-so-massive? =metal/dust-cooling Pop 2 1st sun -> 1st planet, life, human! when and how? need observations Yoshida, Omukai & Hernquist 08

  3. Pop 3 (~Myr ) → Pop 2 (~Gyr)transition: beginning of life? wikipedia article

  4. Omukai+ 05 model collapsing zero/low-metal. protostellar clouds Pop 3 → Pop 2 transition T minimum -> fragmentation H2 dust H2+HD [Z/H]<-6: Mfrag~103MQPop 3 -3<[Z/H]<-5: Mfrag~0.1-100MQPop 2 [Z/H]crit=-5+-1

  5. first Pop 3 stars are (probably) characterized by: What is a “first star”? - very high to high redshift z~60-5? - very low metals/dust Z/Z~<10-5? - very massive M/M>few x100? - luminous UV -> large HII region? - weak wind -> clean environment?? - GRB progenitors? uncertain but probable let’s assume for now Mamma, che cosa è una prima stella? Allora, tesorina…

  6. slide from T. Nagao upper limits on Pop 3 stars

  7. z~60-30? Naoz & Bromberg 07 THE very first GRB Swift detectability 1054 erg/s 1053 1052 expected GRB rate peak energy ~few keV (XRF) long duration ~1000s

  8. c.f. SI, Omukai & Ciardi 2007 MNRAS 380, 1715 high-z GRB afterglows GRBs are: very bright very broadband (<GHz-GeV<) BUT transient

  9. : Ly break spectroscopy in mid IR very high z z>~20 space instruments JWST, SPICA z~60-20 (Ly break >3-7 mm) crude, quick z indicators also useful c.f. SI, Omukai & Ciardi 2007 MNRAS 380, 1715

  10. Compton attenuation in IGM concordance universe Compton thick at z>~56 E>~keV indep. of ionization E>~MeV Klein-Nishina decline tT attenuated spectrum z log nFn log E [MeV]

  11. Schneider+ 06 star formation with first dust PISN Z=0 SNII

  12. very low metals/dust (optical depth at fragmentation) absorption by first dust Schneider+ 06 If such dust-cooling cores exist near a GRB: effects of Pop 3 -> Pop 2 transition or even marginal Pop 3 ([Z/H]~<10-5) observable? also depends on first dust properties other metal lines?

  13. column density of first protostellar cores Yoshida+ 08 log NH,frag column density at fragmentation vs metallicity log(Z/Z) at low metallicity, highly Compton-thick T>>1 By the end of the progenitor’s life: Does all the core material accrete onto the star? May be not. If not, is the remaining material swept out by the HII region? How far? Can dust and/or molecules survive destruction in such material?

  14. GRBs in Compton thick environments Compton downscattering • spectral softening • duration lengthening • variability smearing log(f) possible Pop3 signature? log(E/mec2) T=0, 0.1, 0.3,1,10,30,100 c.f. Compton-thick AGNs central point source in sphere following Sunyaev & Titarchuk 80

  15. - large r~<100 pc - low density n~0.1 cm-3 Pop 3 HII regions - flat profile Can be probed through afterglow evolution? Whalen+ 04

  16. Pop 3 HII regions Kitayama+ 04 Mhalo=106M Mhalo=107M Mstar=200M depends on halo environment

  17. caveats: dust-cooled fragments -> not GRB progenitors? dust distribution in GRB environment effect of progenitor evolution: UV, HII region, wind … destruction by GRB UV+X foreground star forming cores dust GRB rdest star forming cores triggered by photodiss. region driven shock GRB Tsuribe & Omukai 06

  18. Summary and Outlook Questions to Pop 3 theorists GRBs are likely observable out to very high z (~60) Q1. How much core material is remaining in the vicinityof the star (e.g. ~< pc) at the end of its life? If significant, Compton attenuation of prompt emission? In any case, density profile can be probed through afterglow evolution? Q2. How much dust (or molecules) are remainingin such material? If significant, very low (critical) metallicity observable?

  19. ⇔ today’s dust from AGB less formation time, smaller grains → more efficient coolant flatter extinction curve (matches QSO obs.?) first dust from first supernovae PISN Schneider+ 04 but destruction by reverse shock? QSO z=6 Mg2SiO4 Z=0 SNII AC SiO2 AC PISN Schneider+ 06 Maiolino+ 04 Todini & Ferrara+ 01 also Nozawa+ 03, 06, 07

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