1 / 22

Radiative Feedback by the First Stars

This study explores the radiative feedback mechanisms and formation pathways of H2 in high redshift cosmological mini halos using the ZEUS-MP Reactive Flow Radiation Hydrodynamics Code. The results show the evolution of a single halo and its core density, velocity, and fate in the absence of radiation. The study also examines the impact of radiation on star formation and the key role of multifrequency transfer and chemistry in halo dynamics.

fzayas
Download Presentation

Radiative Feedback by the First Stars

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related