18 Apr 2012

  • (abs, pdf) Smit et al., The Star Formation Rate Function for Redshift z~4-7 Galaxies: Evidence for a Uniform Build-Up of Star-Forming Galaxies During the First 3 Gyr of Cosmic Time
  • (abs, pdf) Bradley et al., The Brightest of Reionizing Galaxies Survey: Constraints on the Bright End of the z~8 Luminosity Function
  • (abs, pdf) Gent, Galaxies in box: A simulated view of the interstellar medium

Building the Visualization Lab I: 3D Projection System

I have helped in setting up visualization labs previously in grad school, but I was not involved in choosing the equipment and the details of its construction. Building a visualization lab from the ground up was a totally new experience for me. By posting my experiences, I hope that this series helps people who want to build a similar outfit.

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Optimized Multi-Frequency Spectra

Last week, we submitted a paper titled “Optimized Multi-Frequency Spectra for Applications in Radiative Feedback and Cosmological Reionization” to the Astrophysical Journal.  You can find it on arXiv.  Here we investigate the impact of varying energy discretizations in radiation transport schemes.  Mono-chromatic approximations can underestimate the amount of partial ionization at large radii because all of the ionizing photons are absorbed at some characteristic radius.  This is especially true for X-rays, which have large mean free paths.

With a multi-frequency approach, the solution converges with 4 or more frequency bins. For example with a 10^5 K blackbody source, the temperature of an HII region at r = 8 kpc is underestimated by a factor of 20 if a mono-chromatic spectrum is used.  However it is unclear the best technique on how to choose these frequencies.  In this work, we developed a Monte Carlo scheme to determine optimal frequency values for such radiation calculations.  In the paper, we give optimal discretizations for a 10^5 K blackbody and power law spectrum for 1-4 bins.  The code that employs this method will be released when the paper is accepted.