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)