Band Class Reference

#include <Band.hpp>

Inheritance diagram for Band:

Public Member Functions
double	effectiveWidth () const
double	meanSpecificLuminosity (const Array &lambdav, const Array &pv) const
double	pivotWavelength () const
double	transmission (double wavelength) const
Range	wavelengthRange () const
Public Member Functions inherited from SimulationItem
template<class T >
T *	find (bool setup=true) const
template<class T >
T *	interface (int levels=-999999, bool setup=true) const
virtual string	itemName () const
void	setup ()
string	typeAndName () const
Public Member Functions inherited from Item
	Item (const Item &)=delete
virtual	~Item ()
void	addChild (Item *child)
const vector< Item * > &	children () const
virtual void	clearItemListProperty (const PropertyDef *property)
void	destroyChild (Item *child)
virtual bool	getBoolProperty (const PropertyDef *property) const
virtual vector< double >	getDoubleListProperty (const PropertyDef *property) const
virtual double	getDoubleProperty (const PropertyDef *property) const
virtual string	getEnumProperty (const PropertyDef *property) const
virtual int	getIntProperty (const PropertyDef *property) const
virtual vector< Item * >	getItemListProperty (const PropertyDef *property) const
virtual Item *	getItemProperty (const PropertyDef *property) const
virtual string	getStringProperty (const PropertyDef *property) const
int	getUtilityProperty (string name) const
virtual void	insertIntoItemListProperty (const PropertyDef *property, int index, Item *item)
Item &	operator= (const Item &)=delete
Item *	parent () const
virtual void	removeFromItemListProperty (const PropertyDef *property, int index)
virtual void	setBoolProperty (const PropertyDef *property, bool value)
virtual void	setDoubleListProperty (const PropertyDef *property, vector< double > value)
virtual void	setDoubleProperty (const PropertyDef *property, double value)
virtual void	setEnumProperty (const PropertyDef *property, string value)
virtual void	setIntProperty (const PropertyDef *property, int value)
virtual void	setItemProperty (const PropertyDef *property, Item *item)
virtual void	setStringProperty (const PropertyDef *property, string value)
void	setUtilityProperty (string name, int value)
virtual string	type () const

Protected Member Functions
	Band ()
virtual size_t	dataSize () const =0
void	setupSelfAfter () override
virtual const double *	transmissionData () const =0
virtual const double *	wavelengthData () const =0
Protected Member Functions inherited from SimulationItem
	SimulationItem ()
virtual bool	offersInterface (const std::type_info &interfaceTypeInfo) const
virtual void	setupSelfAfter ()
virtual void	setupSelfBefore ()
Protected Member Functions inherited from Item
	Item ()

Private Types
using	BaseType = SimulationItem
using	ItemType = Band

Private Attributes
const double *	_lambdav
double	_pivot
size_t	_size
const double *	_transv
double	_width

Friends
class	ItemRegistry

Detailed Description

An instance of a Band subclass represents the transmission curve of a particular observational filter as a function of wavelength. Examples include the standard Johnson filters and the transmission curves in each broadband for actual observatories such as GALEX, SDSS or Herschel.

This abstract base class implements the key operations offered by all Band objects: obtaining the transmission at a given wavelength, calculating the mean specific luminosity for a given SED after convolving it with the transmission curve, and determining the pivot wavelength. Subclasses are responsible only for acquiring and serving the data points defining the transmission curve for the band.

Refer to the appendix in Camps et al. 2016 (MNRAS 462, 1057-1075) for a brief introduction of the relevant concepts and a derivation of the corresponding formulas. For the purposes of this class, a band is defined through its arbitrarily scaled transmission curve $T(\lambda )$. The relative transmission at a given wavelength can then be written as

$$T_{\text{rel}}(\lambda )=\frac{T(\lambda )}{max[T(\lambda )]}.$$

Given a spectral energy distribution $L_{\lambda }(\lambda )$, the mean specific luminosity over the band $⟨L_{\lambda }⟩$ can then be obtained through

$$⟨L_{\lambda }⟩=\frac{\int L_{\lambda }(\lambda )T(\lambda )\mathrm{d}\lambda }{\int T(\lambda )\mathrm{d}\lambda }.$$

The pivot wavelength of the band is defined as the wavelength at which the mean specific luminosity can be properly converted between wavelength and frequency representations. It is given by

$${\lambda }_{\mathrm{p}\mathrm{i}\mathrm{v}\mathrm{o}\mathrm{t}}=\sqrt{\frac{\int T(\lambda )\mathrm{d}\lambda }{\int T(\lambda )\mathrm{d}\lambda /{\lambda }^2}}.$$

The effective width of the band is defined as the horizontal size of a rectangle with height equal to the maximum transmission and with the same area as the one covered by the band's transmission curve. It is given by

$$W_{\mathrm{e}\mathrm{f}\mathrm{f}}=\frac{\int T(\lambda )\mathrm{d}\lambda }{max[T(\lambda )]}.$$

As set forth by Camps et al. 2016, for energy measuring devices (bolometers) the total system transmission $T(\lambda )$ is usually given by the instrument designers, and it can be used directly for this class. For photon counters (including all instruments in the UV, optical and near infrared), the total system response $R(\lambda )$ is usually given instead. The transmission curve needed for this class can be derived from the response curve through

$$T(\lambda )=\lambda R(\lambda ).$$

This operation must be performed in a preprocessing step before handing the data to this class.

Also, to further simplify the above formulas, this class requires that the transmission curve provided by a subclass is normalized to unity, i.e.

$$\int T(\lambda )\mathrm{d}\lambda =1.$$

Constructor & Destructor Documentation

Band()

Band::Band ( )

inlineprotected

Default constructor for abstract Item subclass Band : "a wavelength band (transmission curve)" .

Member Function Documentation

dataSize()

virtual size_t Band::dataSize ( ) const

protectedpure virtual

This function returns the number of elements in the wavelength and transmission data arrays held by a subclass.

Implemented in BroadBand, and TabulatedBand.

effectiveWidth()

double Band::effectiveWidth

(

)

const

This function returns the effective width for this band, i.e. the horizontal size of a rectangle with height equal to the maximum transmission and with the same area as the one covered by the band's transmission curve. See the class header for the relevant formulas.

meanSpecificLuminosity()

double Band::meanSpecificLuminosity	(	const Array &	lambdav,
		const Array &	pv
	)		const

This function returns the mean specific luminosity $⟨L_{\lambda }⟩$ for a given SED after convolving it with the transmission curve for this band. See the class header for the relevant formulas.

pivotWavelength()

double Band::pivotWavelength

(

)

const

This function returns the pivot wavelength for this band, i.e. the wavelength at which the mean specific luminosity can be properly converted between wavelength and frequency representations. See the class header for the relevant formulas.

setupSelfAfter()

void Band::setupSelfAfter ( )

overrideprotectedvirtual

This function obtains pointers to the data representing the transmission curve from the subclass and precomputes various values for later use.

Reimplemented from SimulationItem.

transmission()

double Band::transmission

(

double

wavelength

)

const

This function returns the relative transmission $T_{\text{rel}}(\lambda )$ for this band at the specified wavelength. See the class header for the relevant formulas.

transmissionData()

virtual const double * Band::transmissionData ( ) const

protectedpure virtual

This function returns a pointer to the first transmission value in the corresponding array held by a subclass. The number of elements in this array can be obtained through the dataSize() function. The transmission values must be normalized as described in the class header.

Implemented in BroadBand, and TabulatedBand.

wavelengthData()

virtual const double * Band::wavelengthData ( ) const

protectedpure virtual

This function returns a pointer to the first wavelength in the corresponding array held by a subclass. The number of elements in this array can be obtained through the dataSize() function.

Implemented in BroadBand, and TabulatedBand.

wavelengthRange()

Range Band::wavelengthRange

(

)

const

This function returns the wavelength range in which the transmission for this band may be nonzero.

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The documentation for this class was generated from the following file:

• Band.hpp