1999/05/21 by Kenneth Wood, R. J. Reynolds, Ron Reynolds · 6 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/307939
published as Astrophys.J.525:799-807,1999 · Accepted by ApJ, 9 pages, 7 figures
arxiv created 1999/05/21 · openalex publication_date 1999/11/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We present Monte Carlo simulations of the diffuse Hα Galactic background. Our models comprise direct and multiply scattered Hα radiation from the kpc scale height warm ionized medium and midplane H II regions. The scattering is off dust that is assumed to be well mixed with the gas, with an axisymmetric density distribution taken from the literature. The results of our simulations are all-sky Hα images that enable us to separate out the contributions of direct and scattered radiation. We also determine how far the model Hα photons have traveled, i.e., how far we see into the Galaxy at Hα. Our models reproduce the overall characteristics of the observed Hα background and predict that the scattered Hα intensity at high latitudes is in the range 5%-20% of the total intensity, in agreement with estimates based on [S II]/Hα and [O III]/Hα line ratio measurements. The polarization arising from dust scattering of Hα from midplane H II regions is predicted to be less than 1% at high latitude.