Primordial Supernovae and the Assembly

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Primordial Supernovae and the Assembly of the
First Galaxies
arXiv0801.3698
Daniel Whalen Bob Van Veelen X-2, LANL
Utrecht Michael Norman Brian OShea UCSD
T-6, LANL
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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 (OShea,
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)
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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)

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Yoshida, Oh, Kitayama Hernquist 2007
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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

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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
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200 pc
Cosmological Halo z 20
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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
• (gt 1050 photons s-1)
• 2 - 3 Myr lifetimes
• new results extend Pop III lower mass range
  down
• to 15 solar masses (OShea Norman 2007, ApJ,
  654, 66)

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Transformation of the Halo
ZAMS
End of Main Sequence
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Primordial Ionization Front Instabilities
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Final Fates of the First Stars
Heger Woosley 2002
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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

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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
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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

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4 SN Remnant Stages in H II Regions

• t lt 10 yr free-expansion
  shock
• 30 yr lt t lt 2400 yr reverse shock
• 19.8 kyr lt t lt 420 kyr collision with shell /
  radiative phase
• t gt 2 Myr dispersal of the
  halo

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Reverse Shock
Collision with the Shell
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4 SN Remnant Stages in Neutral Halos

• t lt 1 yr free-expansion
  shock
• t lt 20 yr early radiative
  phase
• 100 yr lt t lt 5000 yr late radiative phase
• t gt 1 Myr fallback

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Late Radiative Phase
Fallback
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Enormous, Episodic Infall Rates During Fallback
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Observational Signatures of Primordial Supernovae
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Halo Destruction Efficiency
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Conclusions

• if a primordial star dies in a supernova, it
  will destroy
• any cosmological halo lt 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

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2D Metal Mixing Due to Radiative Cooling
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Thanks!
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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