A Model for the Scattered Light Contribution and Polarization of the Diffuse Hα Galactic Background
Abstract
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1999
- DOI:
- 10.1086/307939
- arXiv:
- arXiv:astro-ph/9905289
- Bibcode:
- 1999ApJ...525..799W
- Keywords:
-
- COSMOLOGY: DIFFUSE RADIATION;
- ISM: DUST;
- EXTINCTION;
- ISM: H II REGIONS;
- POLARIZATION;
- RADIATIVE TRANSFER;
- Cosmology: Diffuse Radiation;
- ISM: Dust;
- Extinction;
- ISM: H II Regions;
- Polarization;
- Radiative Transfer;
- Astrophysics
- E-Print:
- Accepted by ApJ, 9 pages, 7 figures