Correct_vvv_zp is a Python3 library for the correction of the photometric zero points (ZPs)
of the VISTA Variables in the Via Lactea (VVV) ESO Public Survey,
using the method published by
Hajdu, Dekany, Catelan & Grebel (2020).
Specifially, the program correct_vvv_zp.py applies the corrections from
Table 1 of the corresponding paper.
Simply use git clone <URL> to clone this library into a local directory.
Subsequently, it can be added to your PYTHONPATH either temporarily by
issuing the sys.path.append("/your/local/directory") command in python,
or permanantly by exporting you directory into the PYTHONPATH system variable.
For example, if using the bash shell, add the
export PYTHONPATH="${PYTHONPATH}:/your/local/directory" in the ~/.bashrc
file.
Extract the split gzipped tar archive of the binary numpy file zpcorrtable.npy:
cat zpcorrtable.npy.tar.gz.* | tar xzvf -
This library was written and tested in the following python environment:
python 3.8.10, numpy 1.19.5, pandas 1.3.0.
We suggest to use this library in the same environment, created by a virtual environment manager
such as conda.
The corrections are performed by the correct_vvv_zp.py program, that can be run using command-line arguments:
python correct_vvv_zp.py [OPTION]
or by supplying a parameter file that includes the command-line arguments:
python correct_vvv_zp.py @<parameter_file>
The full list of command-line options can be printed on the STDOUT by:
python correct_vvv_zp.py --help
An example parameter file correct_vvv_zp.par is also provided for convenience.
The program processes a list of photometric time series (light curves) stored in separate files, specified
by the --input_list <listfile> parameter. Here, <listfile> must contain a single column with one filename
prefix per line (e.g., star identifiers). By default, each
time series will be read from the file ./<lcdir>/<identifier><lcsuffix_in>,
customizable by the --lcdir and the --lcsuffix_in parameters.
The ZP correction of each measurement is determined based on a number of metadata parameters that must be provided for each data point in the light curve files. These are:
- VVV observation ID (e.g.,
v20100319_00519), suffices of the catalog filenames provided by CASU; - VIRCAM aperture number [1..5];
- VVV tile identifier, e.g., 'b308';
- VIRCAM exposure number, i.e., "HIERARCH ESO DET EXP NO" value in the CASU FITS catalog files' headers. This is an identifier of each (dithered) single VIRCAM exposure (a.k.a. 'pawprint');
- VIRCAM chip number [1..16];
- Modified Julian Date of the observation (MJD-OBS value in the catalog/image headers).
The input light-curve files should contain at least the following columns separated by any number of whitespaces, with their default names provided in parentheses. The required columns are:
VVV observation ID (obsid), VVV tile identifier (tile), VIRCAM chip number (chip), VIRCAM exposure number (expnum), Modified Julian Date of the observation (mjd), Observation time (hjd), magnitude (mag1), magnitude error (magerr1)
The input light curve files are highly customizable with the following command-line parameters:
--usecols <list of column indices> specifies which columns to consider in the input files;
--colnames <list of column names> specifies the custom names of the considered columns;
--apertures <list of apertures> specifies which apertures to consider;
--subset <criteria> specifies custom threshold-rejection criteria in the pandas.dataframe.query format.
If the names of the required columns (see above) differ from the default ones
(shown in parentheses),
these must be explicitly specified by the following parameters:
--colname_obsid, --colname_tile, , --colname_chip,
--colname_expnum, --colname_mjd, --colname_obstime, --colname_mag, and --colname_magerr.
The ZP-corrected light curves are written into the the following files:
./<lcdir>/<identifier><lcsuffix_out>, where <identifier> matches that of the
corresponding input file.
The output files have the following columns: observation time (matching the column
named by --colname_obstime, hjd by default), followed by the corrected magnitude,
its statistical uncertainty, and its ZP error, repeated for each aperture.
A few example uncorrcected VVV light curve files are provided in the test_data subdirectory.
The input list file input.lst contains the corresponding identifiers,
and the correct_vvv_zp.par contains the parameter settings necessary to
correctly process these files.
Try the code with the supplied data and parameter file by the following command:
python correct_vvv_zp.py @correct_vvv_zp.par
The resulting corrected data files can be found in the test_data directory.
Their content should match the corresponding *.dat~ files.
If this library is used in an astronomical research project as provided here or in a modified form, we kindly ask the author to cite the following paper in the resulting publication:
@ARTICLE{2020ExA....49..217H,
author = {{Hajdu}, Gergely and {D{\'e}k{\'a}ny}, Istv{\'a}n and {Catelan}, M{\'a}rcio and {Grebel}, Eva K.},
title = "{On the optimal calibration of VVV photometry}",
journal = {Experimental Astronomy},
keywords = {Photometric calibration, Near-infrared photometry, VISTA, Photometric zero points, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics},
year = 2020,
month = jun,
volume = {49},
number = {3},
pages = {217-238},
doi = {10.1007/s10686-020-09661-0},
archivePrefix = {arXiv},
eprint = {1908.06160},
primaryClass = {astro-ph.IM},
adsurl = {https://ui.adsabs.harvard.edu/abs/2020ExA....49..217H},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
MIT, see LICENSE.