Radiative and Chemical Feedback by the First Stars Daniel Whalen McWilliams Fellow Carnegie Mellon University My Collaborators Joe Smidt (UC Irvine) Thomas McConkie (BYU) Brian OShea (MSU) Mike Norman (UCSD) Rob Hueckstaedt (LANL) Numerical Simulations of Local Radiative Feedback on Early Star Formation Uniform Ionizing/LW Backgrounds Rad Hydro Models of Single Halos Machacek, Bryan & Abel 2001, MNRAS, 548, 509 Machacek, Bryan & Abel 2003, MNRAS, 338, 273 OShea, Abel, Whalen & Norman 2005, ApJL, 628, 5 Mesinger, Bryan & Haiman 2006, ApJ, 648, 835 Mesinger, Bryan & Haiman 2009, MNRAS, 399, 1650 Susa & Umemura 2006, Ahn & Shapiro 2007, MNRAS, 375, 881 Whalen et al 2008, ApJ, 679, 925 Whalen, Hueckstaedt & McConkie 2010, ApJ 712,101 128 kpc comoving The Universe at Redshift 20 ZEUS-MP Reactive Flow Radiation Hydrodynamics Code massively-parallel (MPI) Eulerian hydrocode with 1-, 2-, or 3D cartesian, cylindrical, or spherical meshes 9-species primordial H/He gas network coupled to photon conserving multifrequency UV transfer Poisson solver for gas self-gravity includes the dark matter potential of cosmological halos, which remains frozen for the duration of our calculations 40 energy bins < 13.6 eV, 80 bins from 13.6 eV to 90 eV self-shielding functions of DB 96 corrected for thermal Doppler broadening are used to compute H 2 photo- dissociation Adaptive Subcycling three characteristic timescales emerge when one couples radiation to chemistry and hydrodynamics: the trick is to solve each process on its own timescale without holding the entire algorithm hostage to the shortest time step procedure: (1) while holding densities and velocities fixed, evolve reaction network and gas energy on global min of t chem and t h/c until the global min of t h/c is crossed (2) perform density and velocity updates (the hydro) every t h/c Parameter Space of Surveyed Halos We sample consecutive evolutionary stages of a single 1.35 x 10 5 solar mass halo rather than the entire cluster at a single redshift Since halos in the cluster tend to be coeval, exposing just one at several central densities spans the range of feedback better than a few at roughly the same density We chose this halo mass because it is the smallest in which we expect star formation, so feedback would be less prominent than in a more massive halo Spherically-Averaged Enzo AMR Code Halo Radial Density and Velocity Profiles (OShea & Norman 2007b) z = 23.9, 17.7, 15.6 and 15.0 Evolution of Halo Cores in the Absence of Radiation Halo Photoevaporation Model Grid 023_500pc: complete disruption I-Front Structure monoenergetic: 10 5 K blackbody: quasar: mfp T-Front secondary ionizations by photoelectrons e, T Whalen et al 2008, ApJ, 682, 49 Whalen et al 2010, ApJ, 712, M sol 40 M sol 60 M sol 80 M sol 120 M sol Local Radiative Feedback due to coeval nature of halos within the cluster, feedback tends to be positive or neutral halos with n c > 100 cm -3 will survive photoevaporation and host star formation (accelerated in many instances) feedback sign is better parameterized by central halo density than halo mass radiation drives chemistry that is key to the hydrodynamics of the halo -- multifrequency transfer is a must these results are mostly independent of the spectrum of the illuminating star--more LW photons dont make much difference Nucleosynthetic Forensics of the First Stars Daniel Whalen Candace Joggerst 2010, ApJ, 709, , ApJ, 728, 129 Our Collaborators Ann Almgren (LBNL) John Bell (LBNL) Alexander Heger (University of Minnesota) Stan Woosley (UC Santa Cruz) The Primordial IMF Remains Unconstrained Numerical simulations, although proceeding from well-posed initial conditions, lack the physics to model star formation up to the main sequence (and likely diverge from reality well before) Direct observation of primordial supernovae, in concert with gravitational lensing, may be possible with JWST (Kasen & Woosley 2010; Whalen et al 2011a,b,c, in prep) Stellar archaeology, in which we search for the nucleosynthetic imprint of Pop III stars on low-mass subsequent generations that survive today, is our best bet for indirectly constraining the primordial IMF Final Fates of the First Stars Heger & Woosley 2002, ApJ 567, 532 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]