Public data, code, and notebooks for bar-sizes paper using S4G data

This git repository contains data files, Python code, and Python Jupyter notebooks which can be used to reproduce figures and analyses from the paper "What Determines the Sizes of Bars in Spiral Galaxies?" (Erwin 2019, Monthly Notices of the Royal Astronomical Society, 489: 3553; arXiv:1908.08423).

(This figure, combining two plots from the paper, shows the (deprojected) size of bars from the local, S4G-based sample studied in the paper as a function stellar mass (left) and as a function of exponential disk scale length (right). The logarithm of bar size is a broken-linear function of the logarithm of stellar mass, and a simple linear function of the logarithm of exponential disk scale length (dashed red lines in both panels; the dashed blue line in the left panel shows the best linear fit). The cyan star in the left-hand panel shows the location of the Milky Way's bar, assuming a bar semi-major axis of 5 kpc and a galaxy stellar mass of 5 × 1010 solar masses.)

Dependencies

The Python code and notebooks require the following external Python modules and packages, all of which are available on PyPI and can be installed via pip:

• Numpy, Scipy, matplotlib
• Michele Cappellari's LOESS code: cap_loess_1d

Jupyter Notebooks

There are two Jupyter Python notebooks:

• barsize_fits.ipynb -- generates (and saves to a text file) various fits

• barsizes_figures_for_paper.ipynb -- generates the figures for the paper (using fit coefficients saved by the first notebook)

Python Code

• datasets.py, datautils.py, plotutils.py, s4gutils.py -- miscellaneous utility functions (including statistics).

• sample_defs.py -- definitions of various subsamples of S4G galaxies, in the form of integer lists of index values (slices, more or less).

• fitting_barsizes.py -- code to assist with the fits in the Jupyter notebook barsize_fits.ipynb.

• make_fit_tables.py -- code to generate LaTeX tables for the paper

How to Generate Figures and Analyses from the Paper

1. Download this repository.

2. Edit paths in the notebooks so they point to the correct locations, if necessary. See notes in the initial cells of the notebooks; the main variable you will probably need to edit is plotDir in the second cell of barsizes_figures_for_paper.ipynb, which is where saved PDF figures should go. Also make sure to set savePlots = True if you want the PDF files to actually be generated (the default is False, which means the figures will appear in the notebook but won't be saved to disk).

3. Optionally: Run the notebook barsize_fits.ipynb to generate and save the various fits. (Note that MSE_pred values and parameter uncertainties may change slightly, since they are based on bootstrap resampling.) This is "optional" in that the output files already exist in this directory (they will be overwritten if the notebook is run).

4. Run the notebook barsizes_figures_for_paper.ipynb to generate the figures (it will read the coefficients of the fits from the file generated by running the previous notebook).

Licensing

Code in this repository is released under the BSD 3-clause license.