fconvo

fconvo is a Python module to obtain accurate synthetic photometry given input spectra and filter curves, taking into account whether the filters are photon-counting or energy-counting. It was written by Nadia Zakamska. This module is written for Python 3, and it depends only on numpy, though the tutorial also uses astropy, matplotlib, scipy. If you use fconvo in your research, please cite https://ui.adsabs.harvard.edu/abs/2016MNRAS.455.4191Z/abstract.

There are three functions in fconvo:

1. rebin rebins the spectrum onto another wavelength grid using linear interpolation. Its functionality is similar to many others, including interp1d from scipy. Unlike interp1d, rebin does not break down if the wavelength coverage of the original spectrum is inadequate. Although a flag coverage is returned, all warnings are suppressed, and it's the user's responsibility to check the coverage of the spectral templates used in synthetic photometry.
2. fnu_ave and flam_ave average the flux taking into account filter transmission functions and using equations appropriate for photon-counting and energy-counting instruments.

Among other examples, fconvo uses the SWIRE library of galaxy templates (http://www.iasf-milano.inaf.it/~polletta/templates/swire_templates.html) which are included with fconvo for ease of use. If you download these templates here and use them in your research, please cite the original SWIRE papers (e.g., https://ui.adsabs.harvard.edu/abs/2007ApJ...663...81P/abstract and references therein).

Equations used for photon-counting and energy-counting filters are from here: https://www.astro.ljmu.ac.uk/~ikb/research/mags-fluxes/. In case this webpage disappears, we also provide a pdf printout of this webpage as intro_filter_averaging.pdf.

A limited set of filter curves is supplied with this distribution in the FIL_CURVE directory. The filter curves have their provenance and type (photon-counting vs energy-counting) listed in the headers.

We provide a tutorial Jupyter notebook for this module, tutorial.ipynb. The tutorial consists of preliminaries (imports) and four examples.

In Example 1, a spectrum is rebinned onto a new wavelength grid and shown using matplotlib with the original spectrum and two other implementations of rebinning from SciPy.

In Example 2, AB colors of a galaxy placed at different redshifts are computed.

In Example 3, average F_lambda is shown together with the original spectrum.

In Example 4, synthetic AB photometry of a white dwarf is computed and compared with observed SDSS photometry. In this example, the spectral coverage of one of the bands is inadequate, resulting in a disagreement between synthetic and observed photometry.

Contact

Feel free to contact me: [email protected]

References

The module was originally developed for stitching the orders of Spitzer spectra to match WISE photometry (Hill and Zakamska, 2014, https://ui.adsabs.harvard.edu/abs/2014MNRAS.439.2701H/abstract) and then used for synthetic photometry at other wavelengths (Zakamska et al. 2016, https://ui.adsabs.harvard.edu/abs/2016MNRAS.455.4191Z/abstract)