Filters

Photometric filters in synthesizer are defined using two dedicated objects:

• A Filter object: individual filters defining a filters wavelength coverage and transmission, with related methods and attributes.

• A FilterCollection object: a collection of Filters that behaves like a list and a dictionary, with extra attributes and methods to efficiently work with multiple Filter objects.

We provide a number of different ways to define a Filter or set of Filters:

• Generic: A generic filter simply requires a user defined wavelength array and transmission curve to initialise. A user can then define any arbitrary filter they like using this functionality.

• Top Hat: A top hat filter’s transmission is 1 in a particular range and 0 everywhere else. These are either defined by a minimum and maximum wavelength of transmission, or by the effective wavelength of the transmission and its full width half maximum (FWHM).

• SVO: We also provide an interface to the Spanish Virtual Observatory (SVO) filter service.

  The user need only provide the filter code in “Observatory/Instrument.code” format (as shown on the SVO website) to extract the relevant information from this service, and create a Filter object.

Filters can be used for producing photometry from Sed objects, as well as for creating monochromatic or RGB images.

• Filters example
  • Defining a wavelength array
  • Creating different types of Filter
  • Creating a FilterCollection
  • Working with a FilterCollection
  • Saving and loading FilterCollections
  • Finding a Filter