SpectrumCollection#

class specutils.SpectrumCollection(flux, spectral_axis=None, wcs=None, uncertainty=None, mask=None, meta=None, spectral_axis_index=None, redshift=None, radial_velocity=None, rest_value=None, velocity_convention=None)[source]#

Bases: NDIOMixin, RedshiftMixin

A class to represent a heterogeneous set of spectra that are the same length but have different spectral axes. Spectra that meet this requirement can be stored as multidimensional arrays, and thus can have operations performed on them faster than if they are treated as individual Spectrum objects.

For multidimensional spectra that all have the same spectral axis, use a Spectrum with dimension greater than 1. For a collection of spectra that have different shapes, use SpectrumList. For more on this topic, see Overview of How Specutils Represents Spectra.

The attributes on this class uses the same names and conventions as Spectrum, allowing some operations to work the same. Where this does not work, the user can use standard indexing notation to access individual Spectrum objects.

Parameters:

fluxastropy.units.Quantity: The flux data. The trailing dimension should be the spectral dimension.
spectral_axisastropy.units.Quantity: The spectral axes of the spectra (e.g., wavelength). Must match the dimensionality of flux.
wcswcs object or None: A wcs object (if available) for the collection of spectra. The object must follow standard indexing rules to get a sub-wcs if it is provided.
uncertaintyastropy.nddata.NDUncertainty or ndarray: The uncertainties associated with each spectrum of the collection. In the case that only an n-dimensional quantity or ndaray is provided, the uncertainties are assumed to be standard deviations. Must match the dimensionality of flux.
maskndarray or None: The n-dimensional mask information associated with each spectrum. If present, must match the dimensionality of flux.
redshiftfloat or None: A single value to apply to every spectrum in the collection. Cannot be specified if radial_velocity is specified.
radial_velocityQuantity: A single value to apply to all spectra in the collection. Cannot be specified if redshift is specified.
velocity_convention{“relativistic”, “optical”, “radio”}: Convention used for velocity conversions.
rest_valueQuantity: Any quantity supported by the standard spectral equivalencies (wavelength, energy, frequency, wave number). Describes the rest value of the spectral axis for use with velocity conversions.
metalist: The list of dictionaries containing meta data to be associated with each spectrum in the collection.

Attributes Summary

`energy`	The spectral axis as an energy `Quantity` (in eV).
`flux`	The flux in the spectrum as a `Quantity`.
`frequency`	The spectral axis as a frequency `Quantity` (in GHz).
`mask`	The mask array for the spectrum.
`meta`	A dictionary of metadata for theis spectrum collection, or `None`.
`ndim`	The dimensionality of the collection.
`nspectral`	The length of the spectral dimension.
`radial_velocity`	The radial velocity(s) of the objects represented by this spectrum.
`redshift`	The redshift(s) of the objects represented by this spectrum.
`shape`	The shape of the collection.
`spectral_axis`	The spectral axes as a `Quantity`.
`spectral_axis_index`
`uncertainty`	The uncertainty in the spectrum as a `Quantity`.
`wavelength`	The spectral axis as a wavelength `Quantity` (in Angstroms).
`wcs`	The WCS's as an object array

Methods Summary

from_spectra(spectra)

Create a spectrum collection from a set of individual specutils.Spectrum objects.

Attributes Documentation

energy#: The spectral axis as an energy Quantity (in eV).

flux#: The flux in the spectrum as a Quantity.

frequency#: The spectral axis as a frequency Quantity (in GHz).

mask#: The mask array for the spectrum.

meta#: A dictionary of metadata for theis spectrum collection, or None.

ndim#: The dimensionality of the collection. This is not the same as the dimensionality of the flux et al., because the trailing (spectral) dimension is not included here.

nspectral#: The length of the spectral dimension.

radial_velocity#: The radial velocity(s) of the objects represented by this spectrum. May be scalar (if this spectrum’s flux is 1D) or vector. Note that the concept of “RV of a spectrum” can be ambiguous, so the interpretation is set to some extent by either the user, or operations (like template fitting) that set this attribute when they are run on a spectrum.

redshift#: The redshift(s) of the objects represented by this spectrum. May be scalar (if this spectrum’s flux is 1D) or vector. Note that the concept of “redshift of a spectrum” can be ambiguous, so the interpretation is set to some extent by either the user, or operations (like template fitting) that set this attribute when they are run on a spectrum.

shape#: The shape of the collection. This is not the same as the shape of the flux et al., because the trailing (spectral) dimension is not included here.

spectral_axis#: The spectral axes as a Quantity.

spectral_axis_index#

uncertainty#: The uncertainty in the spectrum as a Quantity.

wavelength#: The spectral axis as a wavelength Quantity (in Angstroms).

wcs#: The WCS’s as an object array

Methods Documentation

classmethod from_spectra(spectra)[source]#

Create a spectrum collection from a set of individual specutils.Spectrum objects.

Parameters:

spectralist, ndarray: A list of Spectrum objects to be held in the collection. Currently the spectral_axis parameters (e.g. observer, radial_velocity) must be the same for each spectrum.