Primordial Supernovae and the Assembly of the First Galaxies

1. Primordial Supernovae and the Assembly of the First Galaxies arXiv:0801.3698 Daniel Whalen Bob Van Veelen X-2, LANL Utrecht Michael Norman Brian O’Shea UCSD T-6, LANL

2. Current Paradigms for the Formation of the First Galaxies assemble a few stars at a time as individual small dark matter halos, each hosting a solitary star, consolidate by mergers form stars consecutively, each in the relic H II region of its progenitor (O’Shea, Abel, Whalen & Norman 2005, Yoshida, et al 2007) in some cases, form stars in both the metals and H II regions of their predecessors (Greif, et al 2007, Wise & Abel 2007)

3. 2nd Star Formation in Relic H II Regions • fossil H II regions of the first stars cool out of equilibrium, • and their temperatures fall faster than they recombine • H2 and HD rapidly form in such circumstances, causing • primordial gas to condense and fragment into new stars • If HD cooling dominates, gas temperatures fall to the • CMB, causing it to fragment on smaller mass scales than • the parent star • this process results in at most a few new stars forming • in the halo of the progenitor on timescales less than • merger times (20 - 30 Myr at z ~ 20)

4. Yoshida, Oh, Kitayama & Hernquist 2007

5. Greif, et al 2007 Wise & Abel 2008 • primordial 1st generation stars explode in their H II • regions • in these numerical scenarios, metals are preferentially • expelled into voids of low density in which star formation • cannot occur • protogalaxies are again built up a few stars at a time • and are contaminated gradually as inflow and mergers • carry metals back into halos, typically on timescales of • 50 - 100 Myr • metallicities greater than 10-3.5 solar can result in a direct • rollover to a low mass 2nd generation

7. Current numerical models fail to properly resolve primordial H II region and supernova dynamics, both of which may lead to a prompt second generation of stars Consequently, the first galaxies may have formed with far greater numbers of stars and different metallicities than now supposed

8. ~ 200 pc Cosmological Halo z ~ 20

9. Properties of the First Stars • thought to be very massive (30 - 500 solar masses) • due to inefficient H2 cooling • form in isolation (one per halo) • Tsurface ~ 100,000 K • extremely luminous sources of ionizing and LW photons • (> 1050 photons s-1) • 2 - 3 Myr lifetimes • new results extend Pop III lower mass range down • to 15 solar masses (O’Shea & Norman 2007, ApJ, 654, 66)

10. Transformation of the Halo ZAMS End of Main Sequence

11. Primordial Ionization Front Instabilities

12. Final Fates of the First Stars Heger & Woosley 2002

13. Primordial Supernova in Cosmological Simulations: Neutral Halos They Fizzle! Yoshida & Kitayama 2005, ApJ, 630, 675 • temperatures skyrocket to 109 K at the center • of the halo • the hot, ionized, dense center emits intense • bremsstrahlung x-rays • the core radiates away the energy of the blast • before it can sweep up its own mass in the halo

14. Recipe for an Accurate Primordial Supernova • initialize blast with kinetic • rather than thermal energy • couple primordial chemistry • to hydrodynamics with • adaptive hierarchical timesteps • implement metals and metal-line • cooling • use moving Eulerian grid to • resolve flows from 0.0005 pc • to 1 kpc • include the dark matter • potential of the halo Truelove & McKee 1999, ApJ, 120, 299

15. ZEUS-MP 1D Primordial Supernova: 9 Models • Halos: 6.9 x 105, 2.1 x 106, and 1.2 x 107 solar masses • Stars: 25, 40, and 200 solar masses (Type II, hypernova, • and pair-instability supernovae) • Stage 1: illuminate each halo for the lifetime of its star • Stage 2: set off the blast and evolve the remnant for 7 Myr

16. 4 SN Remnant Stages in H II Regions • t < 10 yr: free-expansion shock • 30 yr < t < 2400 yr: reverse shock • 19.8 kyr < t < 420 kyr: collision with shell / radiative phase • t > 2 Myr: dispersal of the halo

17. Reverse Shock Collision with the Shell

18. 4 SN Remnant Stages in Neutral Halos • t < 1 yr: free-expansion shock • t < 20 yr: early radiative phase • 100 yr < t < 5000 yr: late radiative phase • t > 1 Myr: fallback

19. Late Radiative Phase Fallback

20. Enormous, Episodic Infall Rates During Fallback

21. Observational Signatures of Primordial Supernovae

22. Halo Destruction Efficiency

23. Conclusions • if a primordial star dies in a supernova, it will destroy • any cosmological halo < 107 solar masses • supernovae in neutral halos do not fizzle--they seriously • damage but do not destroy the halo • primordial SN in H II regions may trigger a second, • prompt generation of low-mass stars that are unbound • from the halo • blasts in neutral halos result in violent fallback, potentially • fueling the growth of SMBH seeds and forming a cluster • of low-mass stars

24. 2D Metal Mixing Due to Radiative Cooling

26. Thanks!

27. Primordial Supernova in Cosmological Simulations: H II Regions • the remnant collides with the dense H II region shell • and later grows to half the radius of the H II region • metals preferentially permeate voids • neither metals nor gas return to the halo in less • than a merger time (~ 50 - 100 Myr) Star Formation is Postponed! Bromm, Yoshida & Hernquist 2003, ApJ, 596, 195L Grief, Johnson & Bromm 2007, ApJ, 670, 1