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Finding The First Cosmic Explosions
Daniel Whalen McWilliams Fellow in CosmologyCarnegie Mellon University
My Collaborators
• Chris Fryer (CCS-2 LANL)
• Daniel Holz (University of Chicago)
• Massimo Stiavelli (JWST / STSci)
• Candace Joggerst (T-2 LANL)
• Lucy Frey (XTD-6 LANL)
• Catherine Lovekin (T-2 LANL)
• Alexander Heger (University of Minnesota)
• Wes Even (XTD-6 LANL)
The WMAP Cosmic Microwave Sky:
a Baby Picture of the Universe ( t ~ 400,000 yr)
128 kpc comoving
The Universeat Redshift 20
~200 pc 100 pc
Filamentary InflowInto a Virialized Haloz ~ 20
Sites of First StarFormation
ENZO AMR Cosmology Code
• Enzo is now a public community research code applied by many research groups to a variety of astrophysical fluid dynamics problems
• PM dark matter / PPM hydro code• includes cosmological expansion• multispecies primordial chemistry and atomic/molecular cooling processes• uniform ionizing and dissociating radiation backgrounds• self-gravity• Compton cooling due to CMB• now has radiative transfer and magnetic fields
density
temperature
0.6 pc 0.06 pc 1200 AU
protostar
disk
Properties of the First Stars
• believed to mostly form in isolation (one per halo), but Pop III binaries have been found to form 20% of the time in recent simulations
• very massive (25 - 500 solar masses) due to inefficient H2 cooling during formation
• Tsurface ~ 100,000 K
• extremely luminous sources of ionizing and LW photons (> 1050 photons s-1)
• 2 - 3 Myr lifetimes
Transformation of the HaloWhalen, Abel & Norman 2004, ApJ, 610, 14
Primordial Ionization Front InstabilitiesWhalen & Norman 2008, ApJ, 675, 644
Final Fates of the First Stars Heger & Woosley 2002, ApJ 567, 532
Mixing & Fallback in 15 – 40 Msol Pop III SNe
Joggerst, .., Whalen, et al 2010ApJ 709, 11
Mixing in 150 –250 Msol Pop IIIPI SNe
Joggerst & Whalen 2011,ApJ, 728, 129
Stellar Archaeology: EMP and HMP Stars
• Hyper Metal-Poor (HMP) Stars:
-5 < [Fe/H] < -4 thought to be enriched by one or a few SNe
• Extremely Metal-Poor (EMP) Stars:
-4 < [Fe/H] <-3 thought to be enriched by an entire population of SNe because of the small scatter in their chemical abundances
No PISN?
• original non-rotating stellar evolution models predict a strong ‘odd-even’ nucleosynthetic signature in PISN element production
• to date, this effect has not been found in any of the EMP/HMP surveys
• intriguing, but not conclusive, evidence that Pop III stars had lower initial masses than suggested by simulation
• this has directed explosion models towards lower-mass stars
Heger & Woosley 2002
Elemental Yield Comparison to HMP Stars
IMF-Averaged Yields and the EMP Stars
Recipe for an Accurate PrimordialSupernova Remnant
• 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
Whalen, et al 2008, ApJ, 682, 49
4 SN Remnant Stagesin 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
Reverse Shock Collision with the Shell:Fragmentation?
Primordial SNe in Relic H II Regions: Enrichment ofthe Dense Shell
Late Radiative Phase Fallback
Explosions in Neutral Halos: Containment
SN Remnant Luminosity Profile in
an H II Region
SN Remnant Luminosity Profile in aNeutral Halo
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
LANL Pop III Supernova Light Curve EffortWhalen et al. ApJ 2010a,b,c in prep
• begin with 1D Pop III 15 – 40 Msol CC SN and 150 – 250 Msol
PI SN blast profiles
• evolve these explosions through breakout from the surface of the star out to 6 mo (CC SNe) or 3 yr (PI SNe) in the LANL radiation hydro code RAGE (Radiation Adaptive Grid Eulerian)
• post-process RAGE profiles with the LANL SPECTRUM code to compute LCs and spectra
• perform MC Monte Carlo models of strong GL of z ~ 20 SNe to calculate flux boosts
• convolve boosted spectra with models for absorption by the Lyman alpha forest and JWST instrument response to determine detection thresholds in redshift
RAGE
• LANL ASC code RAGE (Radiation Adaptive Grid Eulerian)
• 1D RTP AMR radiation hydrodynamics with grey/multigroup FLD and Implicit Monte Carlo transport
• 2T models (radiation and matter not assumed to be at the same temperature)
• LANL OPLIB equilibrium atomic opacity database
• post process rad hydro profiles to obtain spectra and light curves
Post Processing Includes Detailed LANL Opacities
but the atomic levels areassumed to be in equilibrium,a clear approximation
Our Grid of Pop III SN LightCurve Models
• 150, 175, 200, 225, and 250 Msol PI SN explosions, blue and red progenitors, in modest winds and in diffuse relic H II regions (18 models)
• 15, 25, and 40 Msol CC SN explosions, red and blue progenitors, three explosion energies in relic H II regions only
• red and blue progenitors span the range of expected stellar structures for Pop III stars
• core-collapse KEPLER blast profiles are evolved in 2D in the CASTRO AMR code first up to shock breakout to capture internal mixing—these profiles are then spherically averaged and evolved in RAGE to compute LCs
u150
u200
u175
u225
PISN Shock Breakout
• 150 – 1200 eV fireball temperature
• transient (a few hours in the local frame)
Spectra atBreakout
The spectra evolverapidly as the frontcools
Long-TermLight-CurveEvolution
even the lowestenergy PISN at z ~ 10 produces a large signal inthe JWST NIR camera over the first 50 days
Late Time Spectra
spectral features after breakout may enable usto distinguish betweenPISN and CC SNe
larger parameter studywith well-resolved photospheres is now inprogress
Conclusions
• PISN will be visible to JWST out to z ~ 10 ; strong lensing may enable their detection out to z ~ 15 (Holz, Whalen & Fryer 2010 ApJ in prep)
• dedicated ground-based followup with 30-meter class telescopes for primordial SNe spectroscopy
• discrimination between Pop III PISN and Pop III CC SNe will be challenging but offers the first direct constraints on the Pop III IMF
• complementary detection of Pop III PISN remnants by the SZ effect may be possible (Whalen, Bhattacharya & Holz 2010, ApJ in prep)