streamgap-pepper
Exploring the effect of impacts from a CDM-like population of dark-matter subhalos on tidal streams.
This repository contains the code associated with the paper Bovy,
Erkal, & Sanders (2016, BES16), which you should cite if you re-use
any of this code (in addition to, most likely,
galpy). The ipython notebooks used
to generate the plots in this paper can be found in the top-level
directory of this repository. This code uses
galpy and the
streampepperdf.py
galpy extension, which implements the fast calculation of the
perturbed stream structure.
The GIF above shows a GD-1-like stream as it orbits the Milky Way while being perturbed by subhalos at a rate that is three times that naively expected from CDM. Further movies that display the same for different rates can be found in this directory.
There are various useful notebooks, in addition to others that were used during code development that are not described further here; these are all contained in the dev/ subdirectory.
1. GD1Like-simulation-figures.ipynb
(render this notebook on nbviewer, where you can toggle the code)
This notebook contains the figures in Section 2 with the properties of the GD-1-like stream used throughout the paper.
2. meanOperpAndApproxImpacts.ipynb
This notebook contains figures testing the approximations used in the fast line-of-parallel-angle approach to computing the perturbed stream structure:
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The sampling figure that shows that perturbations in the perpendicular frequency direction are much smaller than those in the parallel direction.
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The test of the fast line-of-parallel-angle approach for a single impact compared to a mock sampling and a direct numerical evaluation.
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The test of the fast line-of-parallel-angle approach for four impacts compared to a mock sampling and a direct numerical evaluation.
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The example perturbed density and frequency tracks for different mass ranges and full mass range.
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The scaling of the computational time vs. the number of impacts at different times.
3. StreamPepperAnalysisGD1Like.ipynb
(render this notebook on nbviewer, where you can toggle the code)
This notebook computes the power spectrum of the density and parallel frequency for many different simulations with different parameters. Also contains the bispectrum in these spaces.
4. StreamPepperAnalysisGD1LikeObserved.ipynb
(render this notebook on nbviewer, where you can toggle the code)
Power spectra and bispectra in observed space (density and the stream track's location in the sky, distance, and line-of-sight velocity).
5. galpyPal5Model.ipynb
(render this notebook on nbviewer, where you can toggle the code)
Contains the smooth stream model using galpy.df.streamdf for the Pal 5 data from Fritz & Kallivayalil (2015) and Kuzma et al. (2015).
6. StreamPepperAnalysisPal5LikeObserved.ipynb
(render this notebook on nbviewer, where you can toggle the code)
Contains all code related to the ABC analysis of the Pal 5 data to constrain the number of dark-matter subhalos. Contains the figure with the Pal 5 density, that with densities from the simulations, the power spectrum of Pal 5, and the ABC PDFs. Also contains the analysis of mock Pal 5 N-body simulations with varying amounts of substructure.
7. meanStreamPathDiffs.ipynb
(render this notebook on nbviewer, where you can toggle the code)
This notebook contains the figures of the overall changes to the density profile and track of tidal streams due to subhalo impacts.
8. Simulations
All simulations are run using the code in simulate_streampepper.py. This script has a help function that explains its use. The notes at simulations.rst give some examples of its invocation for many of the simulations that were run.
9. ABC simulations
All ABC simulations are run using the code in run_pal5_abc.py. This script has a help function that explains its use. This function was run with commands like
python run_pal5_abc.py -s pal5_64sampling.pkl --outdens=$DATADIR/bovy/streamgap-pepper/pal5_abc/sims/pal5_t64sampling_X10_6-9_p3_mxp25_dens.dat --outomega=$DATADIR/bovy/streamgap-pepper/pal5_abc/sims/pal5_t64sampling_X10_6-9_p3_mxp25_omega.dat -o $DATADIR/bovy/streamgap-pepper/pal5_abc_bispec/abc/pal5_t64sampling_X10_6-9_polydeg3_minxi0p25_abc.dat -t 64sampling -X 10. -M 6,9 --polydeg=3 --minxi=0.25 -n 50
10. CompareNbodySimulations.ipynb
(render this notebook on nbviewer, where you can toggle the code)
This notebook contains comparisons between the simplified action-angle modeling used in this paper and full N-body simulations with single and multiple impacts.
AUTHORS
Jo Bovy - bovy at astro dot utoronto dot edu
Denis Erkal - derkal at ast dot cam dot ac dot uk
Jason Sanders - jls at ast dot cam dot ac dot uk