abonaca/gd1_spur

Inferring the origin of a spur of stars associated with the GD-1 stream

gd1_spur's Issues

Comments

I submitted some minor changes (typos, grammar) via pull request, and split other comments into two classes: comments to address before submitting, and comments that can be punted until we get the referee report. I put those here so I could use Markdown and you can use the checkboxes to 'resolve' (either to ignore or implement the changes) :)

Before submission:

• I don't love the first clause of the title - it sounds too passive to me. That said, I don't have any great suggestions to make it more active. Maybe something like "The GD-1 stellar stream encounters a massive perturber" or "A massive perturber encountered the GD-1 stellar stream"? Maybe others have suggestions?
• In 4th paragraph of intro, you say "In addition to dark matter subhalos, a number of physical processes can perturb streams at this level" and cite Kupper. But epicyclic over-densities aren't really perturbations. So maybe say "perturb or otherwise alter the morphology of" or something like that?
• 5th paragraph of intro: "studies of stream haps have been statistical in nature" - cite Erkal Pal 5 work?
• Last paragraph of section 2, 1st sentence: missing values for \sigma
• 2nd paragraph of section 3.1: missing value for half-light radius after "initial mass ..."
• Figure 3: it's very hard to see the grey lines (in a printed copy), especially in top panels of leftmost column of panels. How offensive is it to use orange?
• Section 3.2, near chi-squareds. "sigma_gap,i is the associated Poisson uncertainty," but the chi-squared you show is the log of a Gaussian likelihood? So do you evaluate a Gaussian with the Poisson uncertainty?
• "is this an instance of ABC?"
• Figure 4: It's cool to show the whole loops, but for the point about testing predictions, it might be worth somehow highlighting the points that are along the observed spur (i.e. that are near the spline). Maybe make the points near the observed spur alpha=1, but other points alpha=0.5 or something?
• Section 4.1: "for an exoplanet disruption, see ? "
• Figure 5: I'm sorry to keep repeating myself, but I still don't like this figure! I know I'm in the minority, so I will likely be overruled, but I don't like how none of the individual lines are visible, and the colors are hard to parse apart.
• Section 4.2, discussion about GMCs: "These configurations result in a spur that is below the stream at \phi_2 < 0, rather than above at \phi_2 > 0" - is that a typo? If it's at \phi_2 < 0, isn't it by definition below the stream?
• I didn't catch any discussion about the "population of subhalos." I think we discussed and decided that we could just cite out to Erkal and say something along the lines of "1 encounter implies" CDM+Baryon-like order of magnitude.

After submission:

• In section 3.2, I think it's worth discussing that the orbit model ignores explicitly modeling the density of the stream, which is in contrast to the model and discussion about density and the fiducial model. Maybe just add a few sentences to paragraph 2 or 3 of section 3.2?
• Figure 2: Have you tried making the transposed version? I've seen this figure so many times, but my brain still tries to read left-right instead of top-down.