Calibrimbore

One System to rule them all, One System to find them, One System to bring them all and in the darkness bind them.

Calibrimbore creates a composite filter using PS1 grizy filters of the input band. This allows for direct comparison between the well calibrated PS1 system and any other optical photometric system. With calibrimbore we can calibrate all optical photometric systems to PS1.

You can pip install calibrimbore as:

pip install git+https://github.com/CheerfulUser/calibrimbore.git

Applying calibrimbore to obervational data requires the master branch of astroquery so you will need to clone and install the git repo as follows:

git clone https://github.com/astropy/astroquery.git
cd astroquery 
pip install .

We also make use of pysynphot which uses external data libraries. While calibrimbore doesn't use these libraries pysynphot will complain if they are not visible!

Once it is successfully installed, calibrating any optical filter to PS1 is easy and can be done in just a few steps:

from calibrimbore import sauron
comp = sauron(band='path_to_filter',plot=True,system='ab',gr_lims=[-1,.8],cubic_corr=True)

This will go through all the nescissary calibration steps to calculate the linear combination of PS1 filters to best replicate the chosen bandpass, calculate a residual cubic colour correction term and calculate the extinction vector coefficient as a function of colour according to the Fitzpatrick 99 extinction function. Key diagnostic figures and equations that define the composite filter are printed if plot is True.

To get the equations in the ascii string for, you can use the following functions:

comp.ascii_comp()
comp.ascii_cubic_correction()
comp.ascii_R()

To save the composite and correction function coefficients for a filter use:

comp.save_transform(name='test_filter',save_fmt='ascii')

either ascii or csv can be selected for save_fmt.

An instance of calibrimbore can be saved with:

comp.save_state('filename')

this will save out the current configuration of calibrimbore to a dictionary stored in a .npy format. The saved state can then be read in when initialising sauron as:

comp = sauron(load_state='path_to_file')

If you want to calibrate the chosen photometric system you can calculate the composite magnitude for a list of sources with

mags = comp.estimate_mag(ra=ra,dec=dec)

where ra and dec are coordinates in degrees of the sources you wish to use for calibration. Calibrimbore will gather PS1 DR1 observations for these sources via Vizier and calculate their composite magnitudes. We also account for extinction by calculating the expected extinction for stars in a given field using Stellar Locus Regression with the PS1 stellar sources within 0.2 deg of the source.

For more information contact me at: ryan.ridden@canterbury.ac.nz