Radiative Feedback by the First Stars Dan Whalen, T-2, LANL Whalen et al 2008, ApJ, 679, 925 Hueckstadt & Whalen, ApJ, in prep

Our Collaboration Daniel Whalen, T-2, LANL Rob Hueckstaedt, X-2, LANL Brian O’Shea MSU Joseph Smidt UC Irvine Alex Heger U Minn Michael Norman, UC San Diego

~ 200 pc Cosmological Halo z ~ 20

H 2 Formation Pathways in High Redshift Cosmological Minihalos

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 adaptive time step hierarchy enforces respective Courant, heating, and chemistry times without holding the entire algorithm hostage to the shortest time scale Poisson solver for gas self-gravity a separate array serves as a proxy for the dark matter potential, which remains frozen in the course of these 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

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 (O’Shea & 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

I-Front Structure monoenergetic: 10 5 K blackbody: quasar: mfp T-Front secondary ionizations by photoelectrons  e, T

059_500pc

Four Fates of Satellite Halos complete core disruption undisturbed cores accelerated collapse core drainage/partial disruption

023_500pc: complete disruption

40 solar mass star

059_500pc 40 solar mass star

Four Outcomes: halos with n c < cm -3 are completely destroyed anywhere in the cluster halos with n c > 1000 cm -3 are insulated from radiation--collapse is unaffected star formation in halos of intermediate density can be accelerated or delayed depending on how the shock and shadow squeeze the core

Preliminary Conclusions 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 don’t make much difference