FAQ / Planned Changes

FAQ / Planned Changes#

X-ray Model#

  • The rest-frame X-ray wavelength grid should be produced in a very specific way to ensure that your bandpasses are covered, especially at high-z. I currently recommend something like:

    import astropy.constants as const
import astropy.units as u

hc = (const.c * const.h).to(u.micron * u.keV).value
E_lo = 0.5
E_hi = 7.0 # Or whatever is appropriate for you
xray_wave_grid = np.logspace(np.log10(hc / E_hi),
                           np.log10(hc / E_lo),
                           200)
xray_wave_grid /= (1 + redshift)

    Note that the wavelength must be monotonically increasing. This construction will probably be done by default in the future; I’ll also probably change the specification to energy rather than wavelength just to make it more sensible.

Upper Limits and Missing Bands#

  • Upper limits should be specified by setting their flux to 0 and the corresponding uncertainty to the \(1\sigma\)-equivalent limiting flux.

    • The 'exact' upper limit handling should be approached with caution - it needs further testing on real-world data.

    • The 'approx' handling generally suffices to make upper limits behave like upper limits.

  • Missing bands, on the other hand, should be specified by setting the flux to NaN and corresponding uncertainty to 0. Take care when using masked arrays to fill in masked bands - in particular, astropy methods for reading fits tables may convert your data to masked arrays without your knowledge, producing unintended results.

Tests#

  • Multiple of the tests which require model files to be installed are skipped automatically when we upload a new build. You can (and should) run these tests with pytest after installing the code and model libraries locally to make sure you’ve got everything in the right place.

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