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A New Spin on Primordial Hydrogen Recombination and a Refined Model for Spinning Dust Radiation


Ali-Haimoud, Yacine (2011) A New Spin on Primordial Hydrogen Recombination and a Refined Model for Spinning Dust Radiation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/QMFZ-0C90.


This thesis describes theoretical calculations in two subjects: the primordial recombination of the electron-proton plasma about 400,000 years after the Big Bang and electric dipole radiation from spinning dust grains in the present-day interstellar medium.

Primordial hydrogen recombination has recently been the subject of a renewed attention because of the impact of its theoretical uncertainties on predicted cosmic microwave background (CMB) anisotropy power spectra. The physics of the primordial recombination problem can be divided into two qualitatively different aspects. On the one hand, a detailed treatment of the non-thermal radiation field in the optically thick Lyman lines is required for an accurate recombination history near the peak of the visibility function. On the other hand, stimulated recombinations and out-of equilibrium effects are important at late times and a multilevel calculation is required to correctly compute the low-redshift end of the ionization history. Another facet of the problem is the requirement of computational efficiency, as a large number of recombination histories must be evaluated in Markov chains when analyzing CMB data. In this thesis, an effective multilevel atom method is presented, that speeds up multilevel atom computations by more than 5 orders of magnitude. The impact of previously ignored radiative transfer effects is quantified, and explicitly shown to be negligible. Finally, the numerical implementation of a fast and highly accurate primordial recombination code partly written by the author is described.

The second part of this thesis is devoted to one of the potential galactic foregrounds for CMB experiments: the rotational emission from small dust grains. The rotational state of dust grains is described, first classically, and assuming that grains are rotating about their axis of greatest inertia. This assumption is then lifted, and a quantum-mechanical calculation is presented for disk-like grains with a randomized nutation state. In both cases, the probability distribution for the total grain angular momentum is computed with a Fokker-Planck equation, and the resulting emissivity is evaluated, as a function of environmental parameters. These computations are implemented in a public code written by the author.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Cosmology; Cosmic Microwave Background; Primordial Recombination; Galactic Microwave Radiation; Interstellar Medium; Spinning Dust Radiation
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astrophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hirata, Christopher M.
Group:TAPIR, Astronomy Department
Thesis Committee:
  • Kamionkowski, Marc P. (chair)
  • Phinney, E. Sterl
  • Readhead, Anthony C. S.
  • Scoville, Nicholas Zabriskie
  • Hirata, Christopher M.
Defense Date:9 May 2011
Funding AgencyGrant Number
U.S. Department of EnergyDE-FG03-92-ER40701
National Science FoundationAST-0607857 and AST-0807337
Record Number:CaltechTHESIS:05172011-165447651
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6404
Deposited By: Yacine Ali-Haimoud
Deposited On:27 May 2011 20:35
Last Modified:26 Oct 2021 17:20

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