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A2: The 1238 delivery updates MIRI MRS flatfield and photometric calibration reference files, but not aware of any new masking (see https://jwst-crds.stsci.edu/). The NAN pixels appear to be perfectly aligned with your targets, so we think something else might be going on. Please send us a Help Desk ticket with your Program ID number and appropriate screens shots so we can investigate further.
DRL update: On digging into this, the issue is with calwebb_detector1- the pmaps were not actually involved. The relevant line is ultra-bright, and it the CR shower algorithm is mistaking it for the core of a cosmic ray shower and flagging sections of the source around it. This would only affect offline reprocessing since the showers code is OFF by default for MRS. Solution is to turn off the shower-flagging code; there is an existing JP ticket to fix this issue with shower flagging, and this test case has been added as an example to that ticket.
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Q3: In my MIRI MRS data (of 3 galaxies) there is a noticeable absorption feature on the sides of the Ar II emission line at 7 microns. This feature is present in all of my data across the cubes, is this real or perhaps a detector artifact? The Ar II line is very bright, especially in channel 1, but not brighter than other emission lines in my data.
A3: How are you doing background subtraction? It could be that there is an emission feature that is making it into the master background and being subtracted off. This does not seem to be the case for you and it is strange that it is moving around. Please submit a Help Desk ticket to the MIRI team and we will look into it in more detail with you.
DRL update: The problem is cross-artifact bleeding of the ultra-bright emission line between adjacent slices on the detector, which have slightly staggered wavelength solutions. The cross-artifact correction is slightly over-subtracting this signal, as the continuum-optimized correction appears to not be quite ideal for bright emission lines instead. Suggested some modifications to the correction model that could help minimize the artifacts.
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