Find emission processes that contribute to JWST bands for M1-67

[will-henney]

For each of the JWST NIRCAM and MIRI images that we have, we want to find what are the emission mechanisms that contribute to the brightness of the ionized gas.

The primary reason for doing this is that if we understand the mechanisms, then we can potentially derive the densities of the ionized shell from these observations. This would be better than doing it from the HST Ha images because the angular resolution is better for the short wavelength JWST images.

A secondary reason would be to be able to study the warm dust emission in the ionized gas (MIRI bands).

A third reason would be to remove the non-PAH contributions to the f335m, f1130w filters, so we can study the PAH emission from the neutral globules.

In principle, we can have 4 types of contribution to the JWST filters

1. Emission lines. Principally collisional metal lines plus recombination liner of H and He. May also be molecular hydrogen lines from the neutral globules
2. Atomic continuum from the ionized gas. Free-bound and free-free only (since two-photon emission is only in the blue)
3. UIB emission, presumably from PAH molecules. This is important for f335m, f1130w, and possibly f777w
4. Dust emission from very small grains, which will be increasingly important at longer wavelengths

[will-henney]

There are various approaches we could take for predicting the emission processes:

Analytic calculations

Roberto has already made an estimate of the free-free emission using the formulae in Rybicki and in Draine. This gave a result of about 0.2 MJy/sr for the typical EM of the interaction shells.

From Fig 10.2 of Draine book, it looks like the total continuum at 0.9 micron is about 3 to 5 times the free-free, once we add in the recombination to the n >= 4 levels, so this would give about 1 MJy/sr, which is similar to observed shell brightness.

Using PyNeb

This is discussed in its own thread #40

Using Cloudy

In principle, this is the most powerful approach, since we will be using a self-consistent physical model of the region. It would also allow us to predict the dust emission spectrum in addition to the emission lines and atomic continuum.