splus-gaia-astrometry

This Python script calculates the differences between the astrometry (position measurements) from the S-PLUS photometric catalogue and Gaia DR2 or DR3 catalog. The S-PLUS catalogue must be provided, while Gaia is gotten via querying. The code then performs a cross-match between the sources to compare their positions. The results are presented in a figure that shows the difference between the astrometries.

Requirements

The following external packages are required to run the splus-gaia-astrometry.py script:

• astropy: A powerful package for astronomy-related data manipulation and analysis.

• astroquery: A Python package for querying astronomical databases and web services.

• colorlog: A logging utility with colored output.

• gitpython: A Python library to interact with Git repositories.

• matplotlib: A widely used plotting library for creating high-quality visualizations.

• numpy: A fundamental package for scientific computing with Python.

• pandas: A library for data manipulation and analysis.

• statspack (version 0.1.2): A package providing statistical functions.

These dependencies can be installed using pip by running the following command:

pip install -r requirements.txt

Please make sure to install these dependencies before running the splus-gaia-astrometry.py script to ensure smooth execution.

Usage

When using splus-gaia-astrometry.py script, the user shall provide the arguments through the command line. Below is a description of each argument:

python3 splus-gaia-astrometry.py -t list_of_tiles.txt -f tiles_new_status.csv -d astrocatalogs/ -ra ALPHA_J2000 -de DELTA_J2000 -c 2 -nc 4 --percents=[0.3,4.5,32] --savefig --contour

Arguments:

• -t, --tiles (required): List of tiles to be processed.

• -f, --footprint (required): File containing the positions of the S-PLUS tiles.

• -w, --workdir: Work directory path. Default is the current directory.

• -d, --datadir: Data directory path. Default is the workdir.

• -g, --gaia_dr: Gaia catalogue number as registered at Vizier. Default is 355 (Gaia DR3).

• -u, --hdu: HDU number of the catalogue when the catalog is FITS format. Default is 1.

• -ra, --racolumn: Column name of the RA in the catalogue. Default is RA.

• -de, --deccolumn: Column name of the DEC in the catalogue. Default is DEC.

• -m, --mag_column: Column name of the magnitude in the catalogue. Default is MAG_AUTO.

• -fl, --flags_column: Column name of the flags in the catalogue. Default is None.

• -cs, --clstar_column: Column name of the clstar in the catalogue. Default is None.

• -fwhm, --fwhm_column: Column name of the FWHM (Full Width at Half Maximum) in the catalogue. Default is None.

• -sn, --sn_column: Column name of the signal-to-noise ratio in the catalogue. Default is None.

• -a, --angle: Radius to search Gaia sources around the tile center. Default is 1.0 degrees.

• -sl, --sn_limit: Signal-to-noise lower limit to be used in the cross-match. Default is 10.0.

• -o, --output: Output name of the stacked catalogue. Default is results_stacked.csv.

• -b, --bins: Number of bins in the histogram. Default is 1000.

• -l, --limits: Limit of the histogram. Default is 0.5.

• -nc, --ncores: Number of cores to be used. Default is 1.

• --contour: Plot the contour of the Probability Density Function (PDF). Default is False.

• --colours: Colors of the histograms. Default is ['limegreen', 'yellowgreen', 'c'].

• --percents: Percentiles of the contours. Default is 3, 2, and 1 sigma, or [0.3, 4.5, 32].

• -sf, --savefig: Save the figure. Default is False. If True, saves the figure named results_staked.png

• --showfig: Show the figure. Default is False.

• --debug: Prints out the debug information of the code. Default is False.

• -vv, --verbose: Prints out the progress of the code. Default is False.

• --clobber: Overwrite the output file. Default is False.

Example

python3 splus-gaia-astrometry.py -t list_of_tiles.txt -f tiles_new_status.csv -d astrocatalogs/ -ra ALPHA_J2000 -de DELTA_J2000 -c 2 -nc 4 --percents=[0.3,4.5,32] --savefig --contour

The above command will process the specified S-PLUS tiles from the given footprint file and compare their astrometry with Gaia DR3. It will use 4 cores for processing and create a figure (results_stacked.png) showing the difference between the astrometries. The contours in the figure will represent the percentiles entered with the option --percents.

Output

The script will generate a figure named after the --output option that displays the difference between the astrometries of S-PLUS and Gaia. The contours on the figure show the Probability Density Function, indicating the distribution of the astrometric differences.

License

This code is distributed under the GNU GENERAL PUBLIC LICENSE v3.0. Please refer to the LICENSE file in the repository for more details.

Author

The script is authored by Fabio R Herpich and can be reached at [email protected].

Version

The current version of the script is indicated in the code. The latest version can be found on GitHub under the repository herpichfr/splus-gaia-astrometry.

For any questions or issues related to the code, feel free to reach out to the author or open an issue on the GitHub repository.