meeting 2025 05 09 n410 - JacobPilawa/TriaxSchwarzschild_wiki_6 GitHub Wiki

Note: This page is still a work in progress as of 05/09 afternoon.

• Some follow-ups are now posted here.

Doing some follow up work from the meeting yesterday on the additive polynomials for our old galaxies. I've gone back and refit the spectra using adeg=0 and adeg=-1 for N315 and N57, and have some diagnostics below. At this level it does seem like the adeg=-1 cases have elevated moments for both N57 and N315, those N315 seems to be impacted to a slightly less degree than N57. With that said, I'm still trying to sort out why this is the case, and if there is any way to justify our current choices of adeg=-1 for N315 and adeg=0 for N57 as we have in the 'publications' so far.

• (Barth stars) + (bias=0.2) + (starting guess=[0,200]) + (adeg=0). The bullet on the 3/17 page which features fits with adeg=-1 were from my attempts at reconciling the new code with the old code. This was prior to fixing the starting guess bug in the new code. The first results for N57 after fixing the starting guess issue are on the 3/19 page.
• The 3/18 page is very close to the diagnostics below, showing the fits with adeg=0 and adeg=-1, but using the incorrect starting guess (it doesn't seem like the starting guess was as much of an issue for N57 since the spectra all "looked" fine at the time). You're correct that this pages though does seem to show a difference between the adeg=0 and adeg=-1 case, which will be a bit clearer in the plots below.

• The 3/05 page does a decent job at describing our final fits. These used (Barth stars) + (bias=0.2) + (adeg=-1). Notably, our fits were still using the starting guess of [0, 1] km/s for the starting guess, which led to three bins being very poorly fit. We fixed this at the time by taking out 2 of the Barth stars which were contributing to these three spectra's weights.
  • We tested the effect of the starting guess at a later point in time, I think beceause we only discovered the starting guess issue when reprocessing N57. The nice result here is that removing the 2 Barth stars gave essentially identical results for the three problematic bins as changing the starting guess. Rather than refitting everything once again, we moved forward with the 3 stars using only a subset of the Barth library.
• We had used adeg=-1 in the first place due to some issues we were seeing when we fit the spectra ~a year ago. This bullet has some of those plots, showing that that additive polynomial was a very large negative constant and was leading to quite large discrepencies compared to Irina's data.
  • Notably, we were using adeg=-1 before we fixed the bugs we have come to discover, so there's a possibility that using all the correct settings in the first place would have resulted in closer agreement with Irina, and thus we would have never used adeg=-1 in the first place.

• In both cases, the adeg=-1 case are ever-so-subtly worse fit than the adeg=0 case, but this is unsurprising since adeg=0 is effectively a new degree of freedom for the fit.