Webb Office Hours Session 6: April 25, 2024
Q&A's:
Q1: Where are the Webb Office Hours procedures and guidelines?
A1: Webb Office Hours. Type your question into the WebEx chat. We will asynchronously copy questions from the chat to this main page and work through them as a group. If you have images to share please give WebEx permission to share your screen (you may need to log out and log back in again to enable this feature.)
Q2: After flattening an MRS data cube, there are vertical stripes (see below) that are only visible after combining all the data. Should I be concerned.
A2: The striping is near the noise floor. It may be due to cosmic ray showers, artifacts in the flats, correlated noise, etc. This is normal and not a cause for concern.
Q3: The Known Issues page (MR-MRS06) explains that the flux uncertainties for MRS are unrealistically small. Work around to apply method in Law at al. (2023). Is this still the best advice?
A3: Law et al. (2023) describes the impact of covariances that are not treated well in the pipeline. There are other noise contributions that are currently not included by the pipeline. One example is the noise contribution from the darks, which is significant for faint sources. This will be addressed in the next pipeline release. For bright sources, errors in the flat field may be another missing sources of noise. Bottom line, errors are currently underestimated. Empirical bootstrap approach can be used based on the spectrum itself to get a better estimate of the uncertainties.
Q4: Stepping through a JWebbinar 31 notebook works fine for the example data, but my data raises a ValueError: "Too few input images (or groups of images) with non-empty catalogs."
A4: Looking at the data (MIRI imaging), there are very few sources. First try lowering the S/N threshold parameter used by tweakreg. If that doesn't help, try adjusting sharpness, roundness parameters. If that doesn't work, plesae submit a Help Desk ticket, so we can look in more detail.
Q5: PAHFIT was used in Webbinar 23 hosted by the PDRS4ALL team. I can't get PAHFIT to recognize my MRS data.
A5: Contact PAHFIT team via the email address on the page linked immediately above. Other tools are available and may be relevant. A recent paper using CAFE with JWST data is found here , though the tool was developed for Spitzer IRS data, but the paper linked shows that it can be used for MIRI/MRS.
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