Obtain the best estimate of the ionization front radii

[will-henney]

Our initial method for estimating r0 was not very good, since that algorithm was designed primarily for determining the shell radius. We now have some better methods, but we need to intercompare them.

1. Roberto has measured the size of the neutral intensity peaks somehow (@RobeReyes please explain your algorithm and give a link to the notebook or script where you do this)
2. Will has measured the radial displacement between the neutral and ionized peaks. Resulting table is in m1-67/data/reproject/combo-E-ionized-combo-D-neutral-knot-seps.ecsv

[will-henney]

It turns out that the displacement between the peaks of the two neutral combos is even better as a measurement of the globule radius:

• combo-D, which traces the 3.3 micron PAH emission
• combo-DD, which traces the 0.9 micron scattered continuum (we suspect)

This gives the following radial offset:

As compared with the displacement between combo-D and combo-E (ionized emission lines):

• E-D offset: peak 0.10", fwhm 0.10", tail extends to 0.20"
• DD-D offset: peak 0.07", fwhm 0.05", tail extends to 0.20"

It is expected that the DD-D offset should be smaller than the E-D offset because E comes from outside the ionization front, while DD comes from just inside it.

• [ ] The next thing to do with these is to look at correlations between the two and also with the width of the neutral cores

[will-henney]

I have repeated this with the simpler AA combo instead of DD

• AA is just (f150w - 1.05 f090w) and includes neutral knots plus stars
• DD was designed to cancel the stars too and was (AA - 1.36 A) where A = (f150w - 0.6 f210m), so DD = (0.816 f210m - 0.36 f150w - 1.05 f090w)

[will-henney]

So the AA-D displacement is slightly larger than DD-D and shows evidence for a linear increase with radius

[will-henney]

I have a provisional answer to the knot radius

$r_0 = (0.20 \pm 0.02)$ arcsec