How do the heavy element plumes in Cassiopeia A line up with the neutron star?

[OliviaDM]

I was looking at some recent Chandra data of Cassiopeia A, and I'm trying to understand the distribution of heavy elements in the remnant. The map shows these incredible plumes of silicon and iron, but I'm having a hard time reconciling their positions with the suspected location of the neutron star.

[MatthewER]

I dug into the Cas A Chandra maps last month. The Fe rich knots are clumpy and tend to lie inside the remnant, while Si rich plumes snake outward toward the shell. The compact object sits roughly near the center but not smack in the middle of the iron plumes, which makes the simple line up between ejecta and the compact object feel off.

[Ryan.W]

In practice, a lot of the confusion comes from 3D structure. What you see in a 2D X-ray image is a slice through a much messier 3D distribution after 340 years of expansion and a reversing shock. Projection tricks can flip the apparent alignment, and the elements you're tracing were ejected at different times and speeds.

[Gary32]

I once tried to overlay the Fe and Si maps with the measured motion of the central object, and the alignment was not clean. Some iron knots point inward, some silicon features point outward, and the timing of when the reverse shock heated each region matters. It felt like chasing a ghost rather than a single thread.

[Evelyn_L]

One more thought: maybe we’re chasing the wrong thing. If the dynamical center isn’t well constrained, or if the remnant has asymmetric expansion, the NS position relative to heavy-element plumes will look wrong no matter what. Do you have a sense for how the expansion center was defined in your data, and whether there are competing determinations?