Lots of science aside, I love this (unintentionally!) out of focus image of 3I taken on June 24

The best part of the main sorcha paper is the Acknowledgements section ( @megschwamb.bsky.social , I had forgotten we had this paragraph!)

It'd be nice to see if their two period solution reproduces our Fig 6 (which includes the same data they used, and a lot more) ui.adsabs.harvard.edu/abs/2023PSJ....

1/2

Joao and I spend a lot more time than we should discussing how to make pretty plots. Look at this beauty!

Now, with all of these ingredients at hand, we can derive a complete set of population estimates, splitting along each property (color, dynamics). So, in our chosen absolute magnitude range, if our analysis is right, there are ~80k TNOs out there.

Now, let’s look into the inclination distributions. Here, we ask: is there evidence that indicates that, for a dynamical class, the NIRB and NIRF inclination distributions are different? In the case of the HCs, but also the Plutinos, and resonances internal to the Kuiper belt, the answer is yes!

We can also split the color distributions. These are essentially 1D tracks, so we can ask what happens on each half of the distribution. We see (almost) no physical differences, but the NIRB HCs are bluer than the detached NIRBs, whereas the NIRF CCs are redder than the other NIRF populations.

We can break things down even further: the Classical population goes from 100% NIRF to 100% NIRF as it increases in (free) inclination, whereas we don’t see that in scattering or detached pops, they seem well mixed — later on we’ll properly quantify this trend.

Now, we can achieve our initial goal: which percentage of each dynamical class is composed of each color family? CCs are 100% NIRF, whereas the detached, scattering and hot Classicals are ~70% NIRB. Resonances vary, with things inside the 3:2 and 2:1 being more like the CCs.

Something similar happens with the absolute magnitudes: each color family in all dynamical classes have the same abs mag distribution. Even more surprisingly, these two distributions are indistinguishable from each other: there seems to be a universal TNO size distribution in our size range.

So we asked: are there relations between color and lightcurves? We saw dynamical differences in paper I, so we asked if colors also mattered. It turns our, colors are what drive the dynamical differences: NIRF objects, independent of dynamical class, are more variable, as are the cold Classicals.

We took a completely different approach, and arrived at a simpler form of our Equation 8. This form neatly relates TNO orbital parameters, colors, absolute magnitudes and lightcurve amplitudes. This was when things got fun!

Now, we wanted to ask how represented each color family was in each dynamical class. I visited Penn after Thanksgiving 2022, and Gary and I spent an afternoon brainstorming how to do this. Gary thought my GMM likelihood (Equation A8) was wrong, so we rederived it.

With this model, we can probabilistically assign a class to each object. Doing that, we found a few interesting things: the cold Classicals are all NIRF, while the dynamically excited objects are primarily NIRB. This is similar to previous works, so we’re not completely crazy.

Applying this GMM to our data, we found a two component model, separated by their near infrared colors. Surprisingly, this is quite similar to what our Col-OSSOS friends had recently found! We’re calling these components NIRB and NIRF: at a fixed g-r, NIRF is redder.

I can't stop looking at this image... I thought I was the one who liked playing with bad data! Congrats on the paper - I think you told me about it @ ACM last year, good to see it out there