gaiadr3_zeropoint

This Python package contains the necessary tools to query the value of the parallax zero-point for Gaia EDR3 and Gaia DR3. Based on the functions described in Lindegren et al. 2020, the code returns the estimated parallax zero -point given the ecliptic latitude, magnitude and colour of any Gaia (E)DR3 source.

NOTE: the zero-point returned by the code should be subtracted from the parallax value given in the Gaia archive. Run help(zpt.get_zpt) for more details.

Documentation

All classes and methods/functions are documented so use the python help() function to find out more.

Installation

This is a Python3 package (issues may arise if executed with Python2).

The required dependencies are:

• numpy
• pandas (only if you want to use the wrapper provided with the code)

To install the package:

From source (recommended)

1. Clone the Github repository or download the source files
2. cd to the directory
3. Run python setup.py install or python setup install --user for installation in your own home directory

With pip

pip install gaiadr3-zeropoint

Basic usage

Once the package is installed, you can import it in Python:

from zero_point import zpt

Then, first load the coefficient tables by calling the load_tables() function.

Once the tables are loaded, the parallax zero-point can be queried as:

zpt.get_zpt(phot_g_mean_mag, nu_eff_used_in_astrometry, pseudocolour, ecl_lat, astrometric_params_solved)

This function accepts both single values as well as iterables, and returns a float (or array of such) corresponding to the zero-point of the source(s) with those parameters.

NOTE: for 5-p solutions (ra-dec-parallax-pmra-pmdec), the field astrometric_params_solved equals 31 and the pseudocolour variable can take any arbitrary values (even None). On the other hand, for 6-p solutions (ra-dec -parallax-pmra-pmdec-pseudocolour), the field astrometric_params_solved equals 95 and the nu_eff_used_in_astrometry variable can take any arbitrary values (even None).

Finally, if you have a pandas DataFrame (DF) of sources with the columns phot_g_mean_mag, nu_eff_used_in_astrometry, pseudocolour, ecl_lat, astrometric_params_solved, you can simply use the pandas wrapper zpt_wrapper:

zero_point = DF.apply(zpt_wrapper,axis=1) 

Attribution

If you make use of this package for your research, please acknowledge the following papers: Lindegren+20.

Help

If you encounter any problem with the software, please make use of the GitLub Issues page. Otherwise, contact pau.ramos@nao.ac.jp.

Copyright: Pau Ramos, University of Barcelona