sncosmo.get_bandpass

sncosmo.get_bandpass(name, *args, **kwargs)[source]

Get a Bandpass from the registry by name.

This function can return several types of Bandpass objects depending on the bandpass’s variability on the focal plane:

  • Static Bandpass: If the bandpass does not vary spatially on the focal plane, get_bandpass returns a Bandpass instance directly.

  • Radially Variable Bandpass: For bandpasses with radial variability (e.g., megacampsf), an AggregateBandpass instance is returned, which adjusts the bandpass shape based on the specified radius.

  • Position-Dependent Bandpass: For bandpasses that vary with position on the sensor plane (e.g., ztf, megacam6, hsc), the returned object depends on the specified coordinates and sensor ID. If a single location is requested, an interpolated Bandpass instance is returned; if multiple positions are specified, an array of bandpass objects is generated to represent the spatial variations.

Refer to the Examples section for more detailed usage scenarios.

Parameters:
namestr or Bandpass

The name of the Bandpass to retrieve from the registry, or an existing Bandpass object. If a Bandpass object is passed, it is returned directly.

*argstuple, optional

Additional positional arguments, used primarily for radially variable bandpasses (e.g., radius for radial interpolations).

**kwargsdict, optional
Named arguments to customize the Bandpass retrieval:
  • ‘radius’float, optional

    Radius for radial bandpasses (default: 0).

  • ‘wave’array-like, optional

    Wavelength grid for an interpolated Bandpass.

  • ‘x’, ‘y’float, optional

    Spatial coordinates for 2D interpolation.

  • ‘sensor_id’int, optional

    Sensor ID for multi-sensor configurations (default: 1).

  • ‘filter_frame’bool, optional

    If True, applies a filter frame (default: False).

Returns:
Bandpass or ndarray

  • If the name corresponds to a static Bandpass: returns the Bandpass object.

  • If the Bandpass is radially variable: returns the interpolated Bandpass object at the specified radius.

  • For general interpolated Bandpasses (2D or multi-sensor): returns an array of transmission values, or a Bandpass object if only one spatial filter is evaluated.

Raises:
TypeError

If the parameters provided in *args and **kwargs are invalid

Notes

  • Uses _BANDPASSES and _BANDPASS_INTERPOLATORS to retrieve static and interpolated Bandpasses, respectively.

  • The general case applies to configurations like ZTF, MegaCam, and HSC, where multidimensional interpolation grids are used.

Examples

Basic usage with a static Bandpass: >>> bandpass = get_bandpass(‘ztfg’)

Using a radial Bandpass with a specific radius: >>> radial_bandpass = get_bandpass(‘megacampsf::r’, radius=1.2)

Specifying spatial coordinates and a sensor ID for the Bandpasses managed by a GeneralBandpassInterpolator >>> interpolated_bandpass = get_bandpass( … ‘megacam6::g’, x=2355.22, y=1222.4, sensor_id=12)

Specifying a vector of spatial coordinates and sensor ids >>> x = numpy.random.uniform(0., 2048., size=100) >>> y = numpy.random.uniform(0., 4600., size=100) >>> sensor_id = numpy.random.randint(0, 36, size=100) >>> interpolated_bandpasses = get_bandpass( … ‘megacam6::z’, x=x, y=y, sensor_id=sensor_id)

Using a custom wavelength grid >>> x = numpy.random.uniform(0., 3000., size=100) >>> y = numpy.random.uniform(0., 3000., size=100) >>> sensor_id = numpy.random.randint(0, 65, size=100) >>> wave_grid = numpy.random.linspace(3000., 11000., 8000) >>> custom_wave_bandpass = get_bandpass(‘ztf::r’, wave=wave_grid)