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Radiative Feedback by the First Stars Dan Whalen, T-2, LANL

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

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Radiative Feedback by the First Stars Dan Whalen, T-2, LANL

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

  2. 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

  3. ~ 200 pc Cosmological Halo z ~ 20

  4. H2 Formation Pathways in High Redshift Cosmological Minihalos

  5. The Universe at Redshift 20 128 kpc comoving

  6. 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

  7. 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 H2 photo- • dissociation

  8. Parameter Space of Surveyed Halos • We sample consecutive evolutionary stages of a single • 1.35 x 105 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

  9. 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

  10. Evolution of Halo Cores in the Absence of Radiation

  11. Halo Photoevaporation Model Grid

  12. I-Front Structure monoenergetic: 20 - 30 mfp e, T 105 K blackbody: e, T T-Front quasar: e, T secondary ionizations by photoelectrons

  13. 059_500pc

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

  15. 023_500pc: complete disruption

  16. 40 solar mass star

  17. 059_500pc 40 solar mass star

  18. Four Outcomes: • halos with nc < 2 - 3 cm-3 are completely destroyed anywhere in the cluster • halos with nc > 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

  19. Preliminary Conclusions • due to coeval nature of halos within the cluster, feedback • tends to be positive or neutral • halos with nc > 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

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