Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2010-06-30
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
25 pages, 7 figures, 4 tables, single column, details of the calculation and atomic physics added, accepted by ApJ
Scientific paper
Recent observations have found the ratio of H-alpha to free-free radio continuum to be surprisingly high in the diffuse ionized ISM (the so-called WIM), corresponding to an electron temperature of only ~3000K. Such low temperatures were unexpected in gas that was presumed to be photoionized. We consider a 3-component model for the observed diffuse emission, consisting of a mix of (1) photoionized gas, (2) gas that is recombining and cooling, and (3) cool H I gas. This model can successfully reproduce the observed intensities of free-free continuum, H-alpha, and collisionally-excited lines such as NII 6583. To reproduce the low observed value of free-free to H-alpha, the PAH abundance in the photoionized regions must be lowered by a factor ~3, and ~20% of the diffuse H-alpha must be reflected from dust grains, as suggested by Wood & Reynolds (1999).
Dong Ruobing
Draine Bruce T.
No associations
LandOfFree
H-alpha and Free-Free Emission from the WIM does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with H-alpha and Free-Free Emission from the WIM, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and H-alpha and Free-Free Emission from the WIM will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-427977