Angular lightcone #313
Angular lightcone #313
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would it be possible to include some visualizations for this PR, showing the two options?
… On 24.11.2022., at 08:38, Steven Murray ***@***.***> wrote:
@steven-murray <https://github.com/steven-murray> requested your review on: #313 <#313> Angular lightcone.
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@andreimesinger Ah, yes that was always my intention. I'll get to that ASAP. |
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I feel like adding a new section to the lightcone tutorial (or a new tutorial entirely) would also be great |
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@JulianBMunoz that's a great section. In fact, I'm currently updating the lightcone tutorial with this (that was the notebook we were looking at last week with the weird aspect ratio plot). |
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OK @andreimesinger and @JulianBMunoz, I'm gonna post some plots here, but also these plots are all available in the updated documentation here. First, I made an angular grid that was suppose to closely match the rectilinear grid (at least at the lowest redshift), and looking directly at the face of the lightcone, we get:
Then, looking at the redshift evolution (top is rectilinear, bottom is angular):
Of course, the angular lightcone in the above is plotted as if it were rectilinear, so we can also plot it in polar coords:
And, just to prove that we're not limited to doing small areas of the sky corresponding to the rectilinear lightcone, I simulated a "lightplane" -- i.e. a single strip along the horizon, extending into the line of sight. Plotting that in polar coords:
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beautiful! i love the lightplane!!On 13 Dec 2022, at 22:50, Steven Murray ***@***.***> wrote:
OK @andreimesinger and @JulianBMunoz, I'm gonna post some plots here, but also these plots are all available in the updated documentation here.
First, I made an angular grid that was suppose to closely match the rectilinear grid (at least at the lowest redshift), and looking directly at the face of the lightcone, we get:
Then, looking at the redshift evolution (top is rectilinear, bottom is angular):
Of course, the angular lightcone in the above is plotted as if it were rectilinear, so we can also plot it in polar coords:
And, just to prove that we're not limited to doing small areas of the sky corresponding to the rectilinear lightcone, I simulated a "lightplane" -- i.e. a single strip along the horizon, extending into the line of sight. Plotting that in polar coords:
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The "face" slices you posted look a bit weird.. The angular one looks smoothed and is missing some large structures compared to the rectilinear one.... |
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Yeah -- so I think it's all as expected. At the top left corner, the match is very very close, because the (0,0) pixel of the angular lightcone perfectly corresponds to the rectilinear. However, moving away from there, the angular lightcone bends away from the rectilinear, and so it is showing effectively a different slice at the bottom right. The smoothing I'm not quite sure -- probably an interpolation thing. Probably if I created the angular lightcone at double the resolution, it would look more crisp. |
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This is unavoidable. An interpolated 21-cm signal will always be blurry as there is no way to interpolate between the sharp edges of the ionised regions. It inevitably always leads to blurry features around ionised regions. Increasing the resolution will not help this. |
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In terms of power spectrum, though, this shouldn't be a big deal as it should only affect very small scales, right? I guess it's something we should test. |
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This is what I was going to ask, does the power spectrum change much
between the rectangular and angular coordinates?
…On Mon, Dec 19, 2022 at 9:46 AM Steven Murray ***@***.***> wrote:
In terms of power spectrum, though, this shouldn't be a big deal as it
should only affect very small scales, right? I guess it's something we
should test.
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@JulianBMunoz I can take the (cartesian) power spectrum of the angular lightcone, which is slightly the wrong thing to do because the coordinates aren't exactly rectilinear. OR I can compute the angular power spectrum after tiling onto a full healpix map (this is a bit more compute heavy, obviously). For the latter, I can never remember exactly how to relate the angular PS back to the 3D PS in a simple way, so I'm less sure it'll be useful. |
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I think in order to compare more fairly it may make sense to compare angular power spectra, so C_\ells. In the case of the rectilinear lightcone one can take the flat-sky approximation or similar to compute the C_ells. Ping me on Slack if you want to chat more |
Codecov ReportAttention:
Additional details and impacted files@@ Coverage Diff @@
## master #313 +/- ##
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- Coverage 86.58% 82.42% -4.17%
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Files 12 13 +1
Lines 2811 3106 +295
Branches 0 841 +841
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+ Hits 2434 2560 +126
- Misses 377 391 +14
- Partials 0 155 +155 ☔ View full report in Codecov by Sentry. |
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@andreimesinger + @JulianBMunoz this PR is now ready for final review/approval. It's kinda large and unwieldy, but all tests are passing and I've even added tests of the documentation tutorials. The validation of the new lightconing method is in the lightcone tutorial. |
This PR adds the ability to create lightcones in Angular coordinates (as well as a more flexible lightconing interface).
In total, it does the following:
Lightconerbase class, and two implementations: aRectilinearLightconer(equivalent to the old way) and anAngularLightconer.lightcone_coordsattribute of theLightConeclass.AngularLightconeclass to deal with the outputs of these lightcones.