1. The Population III Connection Jonathan Devor

2. Outline GRBs as Cosmological Probes: Why is this interesting? Population III – A brief historical overview The primordial IMF Stars: Then and now Supernovae What can we hope to see? The road ahead

3. GRBs as Cosmological Probes: Why is this interesting? Cosmological model Big bang nucleosynthesis First stars (population III) Galactic formation Reionization epoch Early IGM metallicity enhancement

4. Population III – A brief historical overview (Baade 1944) – star populations: Pop. I: Sun-like (1 - 2% metals by mass) Pop. II: Globular cluster-like (0.01 – 0.1%) Pop. III: No metals (actually < 0.001%) (Schwarzschild et al. 1953): First model for pop. III stars (far less complex than type I stars in a modern environment)

5. Ongoing work 1980’s: Cosmological consequences- -Effects on CMB (SZ effect) -“Primordial” abundances of Helium - “Pregalactic metal enrichment” -Reionization epoch -Effects on early galactic formation 1990’s: clump/star formation 2000’s: WMAP, Swift, JWST

6. Space Missions… BATSE (1991-2000) = Burst and Transient Source Experiment [5-1,500 keV ] WMAP (2003-) = Wilkinson Microwave Anisotropy Probe [22-90 GHz] Swift (2004-) JWST (2011-) = James Webb Space Telescope EXIST =Energetic X-ray Imaging Survey Telescope 5-100 KeV: x10-20 better than Swift 100-600 KeV: x300 better than HEAO-A3 survey

7.  CDM at z=17 Taken from (Yoshida 2003) Taken from Swift website

8. Primordial gas Taken from (Bromm 2002) Adiabatic H 2 cooling Stable pointGravity compression Lingers at: T~200K

9. Jean’s instability criterion

10. Protostellar collapse No dust, no metal – need H 2 as coolent - Free electron catalyzer (feedback from UV) - 3-body channel  Clump breakup Radiation pressure dominated (very low opacity- electron scatter) Halo breakup N star ~ 1-5 (if N=1, problem getting rid of the angular momentum)

11. Clump evolution Taken from (Omukai 1998)

12. Growth of protostar The accretion is effectively shut off at some critical value because of the dramatic increase in radius Taken from (Omukai 2003)

13. Pop. III supernovae < 140 M  Type II SNe (core collapse) Low yield 140-260 M  Pair-instability supernova (PISN) No remnant High yield ½M  metals > 260 M  Massive black hole ( MBH) High accretion No yield (quasar?) Life time:

14. Pop. III star – remnant 400 pc fragmentation metals Taken from (Bromm 2003) SPH simulation

15. Reionization HI13.6 eV HeI24.6 eV HeII54.4 eV Though comparable in brightness, GRB afterglows release less energy than quasars into the IGM (ionizes M  of hydrogen ). So they have a negligible effect on their environment (with the exception of dwarf galaxies ) Taken from (Wyithe 2003)

16. What can we see? All GRBs Swift BATSE Taken from (Bromm 2002) With Swift, 10-25% of GRB afterglows will come from z > 5 That is, about a dozen a year! Taken from (Lamb 2002)

17. The road ahead – open questions Do pop. III stars exist? Need observations!!! (Swift?) Do their supernovae make GRBs? (quenching?) Primordial environment Primordial IMF / star formation history (GRB redshift distribution) Early cosmological formation (filaments, galaxies) “Extreme physics” (SNe, MBH)

18. Some references Historical: -Schwarzschild M., ”Inhomogeneous Stellar Models. III. Models with Partially Degenerate Isothermal Cores.”, 1953, Astrophysical Journal, vol. 118, p.326 Survey papers: - Bromm V. and Larson R., “The First Stars”, 2003, astro-ph/0311019 - Bromm V., “ The First Sources of Light ‘, asyro-ph/0211292 - Lamb D., “Gamma-Ray Bursts as a Probe of Cosmology”, 2002, astro-ph/0210434 - Loeb A. and Barkana R.,”The reionization of the Universe by the First stars and Quasars”, Annu. Rev. Astron. Astrophys., 2001, 39:19-66 - Loeb A., “Observing the First Stars, One Star a Time”, 2003, astro-ph/0307231

19. The Swift Song We know that gamma ray explosions happen randomly all over the sky (It's like a lottery: a ticket for each square degree) You see a FLASH! and then there's not another till about a day has gone by (But that depends upon detector sensitivity) In just a moment they spew energy worth (That's pretty fast) A value we can't even fathom on Earth (It's really vast!) But just what's giving rise to gamma ray sparked skies? Is it the death cry of a massive star or black hole birth? (Or both, or both? or both!) Chorus: Swiftly swirling, gravity twirling Neutron stars about to collide Off in a galaxy so far away Catastrophic interplay A roller coaster gamma ray ride Superbright explosion then Never to repeat again How are we supposed to know? How about a telescope rotation Swiftly onto the location Of its panchromatic afterglow?