meeting 2025 05 08 n410 - JacobPilawa/TriaxSchwarzschild_wiki_6 GitHub Wiki

Context

  • Checking out the additive and multiplicative polynomials a bit more carefully here since they seem to be behaving a bit weird.

  • It seems like we did do a bit of testing on the additive and multiplicative polynomials for NGC57/NGC 315:

  • Takeaways:

    • It seems I can do a pretty decent job of reproducing Irina's results using the symmetrically-binned data using the settings she lists on BOX/in Massive XIII.
    • One thing I noticed, though, is that the settings that she uses for the Mitchell data appear to use a multiplicative degree of 7 for the data, but still uses an additive polynomial of degree 0. I've never reprocessed the Mitchell spectra so unsure how this was deteremined, or if this should be in the back of our mind when we compare the GMOS and Mitchell data near the overlapping region.
      • We used adeg=0 for N2693/N57, but for N315 we switched it off due to the additive polynomial being quite negative, but I don't think we took a lot of time to understand this or properly test this after we fixed all the spectral fitting issues.
    • When I change the settings on BOX to leave off the additive polynomial, I get some tension in the kinematics. Turning the additive polynomial off seems to raise our moments relative to having the additive polynomial in the mix.

Diagnostics

  • Up to now, as usual, I've been fitting the non-symmetric Voronoi binning scheme data, but I've switched over to the symmetric binning scheme data to do some of this testing. There are a number of files on BOX that look like the text below containg what I think are the parameters for pPXF used in the fitting. I grabbed the N777 one for now (I can't seem to track down an equaivlent for N410, but the files I've looked at have been virtually identical). This at least gave me a baseline to work with.
    • Interestingly, Massive Paper XIII explicitly states that the starting guess for (V, sigma) = (0, 250) rather than (0, 200), so I've adopted that starting guess for comparison.

Nominal settings for pPXF fits to NGC 777 GMOS data
---------------------------------------------------

Wavelength range (rest):  8420-8730 A

Template list:  barthlist.txt
(15 stars from Barth et al. 2002 -- spectra are from MILES Calcium Triplet library)

Spectrum mask:  /GMOS/galaxy_files/N777/spectra/N777_spectra_mask1_nochipgap.fits
(bright sky lines as assessed from inspection of GMOS spectra)
(GMOS chip gap lies outside the pPXF wavelength range)

Initial velocity shift: 5000 km/s

Multiplicative polynomial: degree 3

Additive polynomial: degree 0  (constant offset)

Bias parameter: 0

  • So given this, I'v fit the symmetric spectra with adeg=0 and adeg=-1, and have some diagnostics below compared to Irina's kinematics:

    • Note that Irina's kinematics are not actually on BOX it seems -- again, maybe Emily has this on one of her hard drives -- but I was able to find a version of the kinematics here, in one of the old wikis that I can compare to.
    • Note that the two cases below I've been calling Case A sym and Case B sym, where Case A uses adeg=0, and Case B uses adeg=-1.

  • Here's the spectra for Case A and Case B:

Case A
Plot
Case B
Plot
  • And the RMS vs. spectrum number:
    • Note that the Case B spectra are ever-so-slightly worse fit than the Case A spectra:
Case A Case B
  • And here are some comparisons of the spectra against one another:
    • I don't have access to Irina's preliminary moments it seems; the only data that are on the Github seem to be just before running models, so these are after doing 100 MCs and taking the median:
Case A vs. Irina Case B vs. Irina Case A vs. Case B

Comparing Radial Moments

  • I've now got a few examples of the radial profiles for Irina's data compared to my Case A and Case C, as well as my Case A sym.
  • Again, Case A here has adeg=0, whereas Case C has adeg=-1. In the case where I use identical binning schemes, the radial profiles are in excellent agreement as we would expected from the 1-to-1 plots above.
  • When I plot the radial profile for the symmetric binning vs. non-symmetric binning, I seem to have very nice agremeent with Case A (adeg = 0), and we see this offset in the moments for Case C (adeg=-1). Because Irina's data uses adeg=0, and my Case A uses adeg=0 and gets nice agreement (even for different binning schemes), I'm inclined to trust the adeg=0 cases more than the adeg=-1 cases.
    • And again as a quick reminder, I can't find a fiducial fit from Irina anywhere so these compare the MC moments (without errors).
Irina + Case A Irina + Case C Irina + Case A sym
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