Curated collection of the best bow shock shells

[will-henney]

In each of the spatial groups, we want to find the best examples of a well-separated bow shock shell if any exists.

This is most easily done using rgb color images. I will will use two different ones:

1. f1130w, f150w, f090w
2. combo-d-neutral, f656n, combo-e-ionized

Both show the knots in red and the shells in blue-green or gray. The first has big low-resolution blobs for the neutral knots, but shows the ionization front and the shells in the highest possible resolution. The second has almost matched resolutions in the three bands.

[will-henney]

Groups E-13, E-20, and E-27

These groups contain many closely spaced knots, including some weak ones that we have not included in our list yet.

There are some shells that seem well detected:

PA088-R273 is the farthest one and has a nice detached shell that fully envelopes the knot, icluding along the flank of the tail. It has a sharp interior edge, but a diffuse outer edge.

PA090-R158 is in a bit of a complicated region, but it has a nice shell about 1 arcsec in front of the knot. Note that the tail is not quite radial and the shell seems to have an axis similar to the tail.

PA097-R151 is a smaller knot just below the previous one, which also has a detached shell.

PA084-R112 Is the closest in and shows several overlapping shells, but we can take the one closest to the axis, although I am not convinced this a normal stand-off shock. These shells might be related to the jet discussed below.

There is also a shell in front of the biggest and brightest knot PA085-R202 (arrow on first image) but that looks like it might be caused by jet. There is a string of knots and filaments that extends back towards the star.

Note that there are several knots that are not in our list. For instance, the two that are below PA092-R204. The lower one of these has a detectable detached bow shock shell, so it might be worth expanding our list

[will-henney]

Groups E-13 (part), NE-04, N-10, W-08

(As an aside, it might be better to split off this part of E-13 – maybe call it NE-13, since it seems distinct from the more easterly arm)

Group NE-04

This group seems to be at a very high inclination angle, seen face-on based on the kinematics evidence. It shows a very distinct morphology for the shells, with many presenting as full circles, rather than semi-circles.

PA028-R054 is one with a full circular shell. And strangely the center of the shell seems displaced towards the star from the center of the knot, which is not what I would expect. The starward side of the shell does get a bit lost in the psf and other inner knots in the region. We might have to use a polynomial background to get a decent fit.

PA058-R044 is in a slightly cleaner region and is surrounded by a rather large shell.

PA031-R033 is possibly the brightest knot in the entire nebula and has a more conventional-looking shell. Arguably this knot should be in a different group, together with two other knots at even smaller radii that are also very bright (not included in our list).

Group NE-13

PA042-R077 is right under a diffraction spike in the jwst images, but is quite clean in H alpha and shows a nice parabolic shell. Its near neighbor PA039-R083 also has a nice shell, although one side of it crosses the core of PA042-R077

PA034-R126 is the innermost of a chain of large-ish bright knots and has nice clean bow shock shell in front of it. The f150w image shows that the inner boundary of the shell is very sharp.

PA042-R168 is somewhat affected by the diffraction spike, but otherwise is a nice clean shell.

Group N-10

PA005-R101 is the most well-isolated knot in this group, which shows an easily identifiable shell. Many others (PA357-R101, PA356-R098, etc) are all close together so that their shells overlap.

PA330-R077 has a very squashed-down and broad shell, which is not very well separated from the knot.

Group W-08

PA290-R104 is small faint knot that has a detectable shell, although it is not well detached (partly due to resolution)

[will-henney]

Group N-16

This group shows a high degree of clustering between the knots. There are several radial chains of knots, with fainter knots on the inside and brighter knots on the outside, such that it is not always clear whether the shells are from the single knot in front or from the collective action of several bigger knots outside of them.

PA357-R148 and its neighbor PA353-R145 are the two innermost knots in this group, but their shells are quite different. PA353-R145 has a sharper, thinner, fainter shell, which is well detached. PA357-R148 has a much more diffuse but brighter shell, but this might be partly due to overlap with other shells from knots such as PA360-R153 and others that are hidden in the glare from a bright star. Alternatively, it could be due to differences in knot size (PA353-R145 is smaller) and possibly inclination angle.

PA347-R159 is another small knot, with a nice clear shell but that seems to be superimposed on a bigger shell formed by the group of knots around PA348-R166, which itself is at least two knots.

PA355-R163 has a suspiciously large and elongated shell, which might be something to do with the knots PA356-R175 and friends.

PA005-R178 has a similar situation with PA006-R185