Transmission Curves

Available Transmission Curves

The available transmission curves are described here

They are also listed within the code via

from sedpy import observate
observate.list_available_filters()

Adding Transmission curves

Each transmission curve should be in its own file named filter_name.par, where filter_name is a unique identifier that will be used to identify the filter in the code (e.g., galex_FUV.par).

Then, make <filter_name>.par a two-column space delimited ascii file where the first column is wavelength in Angstroms and the second column is detector signal per photon (arbitrarily normalized). Comments must be preceded by a #. Then you can access it in python easily with e.g.

from sedpy import observate
filt = observate.Filter("filter_name", directory="/path/to/the/file/")
filt_list = observate.load_filters(["filter_name"], directory="/path/to/the/file/")

If using load_filters then all transmission files must be in the same directory. Optionally you can place the files you create in the <download_dir>/sedpy/sedpy/data/filters/ directory and reinstall with cd <download_dir>/sedpy; pip install .. Then you don’t need to specify the directory keyword.

The new filter will now be accesible using filter_name

from sedpy import observate
filt = observate.Filter("filter_name")

Finally, you can simply pass a tuple of (wavelength, transmission):

from sedpy import observate
filt = observate.Filter("filter_name", data=(wavelength, transmission)

Vega reference

By default sedpy produces AB magnitudes. However, for each filter a conversion to Vega zeropoints is computed. This is based on a Vega reference spectrum from the HST calspec database, as discussed in Bolin07 and Bohlin14 . The version used corresponds to the one here .