StellarSurfaceSource Class Reference

#include <StellarSurfaceSource.hpp>

Inheritance diagram for StellarSurfaceSource:

Public Member Functions
int	intrinsicDimension () const override
void	launchSpecialty (PhotonPacket *pp, size_t historyIndex, double lambda, double Lw, VelocityInterface *bvi) const override
double	stellarRadius () const
Public Member Functions inherited from CenteredSource
double	centerX () const
double	centerY () const
double	centerZ () const
int	geometryDimension () const override
virtual int	intrinsicDimension () const =0
Public Member Functions inherited from SpecialtySource
int	dimension () const override
virtual int	geometryDimension () const =0
bool	hasVelocity () const override
void	launchNormalized (PhotonPacket *pp, size_t historyIndex, double lambda, double Lw) const override
virtual void	launchSpecialty (PhotonPacket *pp, size_t historyIndex, double lambda, double Lw, VelocityInterface *bvi) const =0
Vec	velocity () const override
double	velocityX () const
double	velocityY () const
double	velocityZ () const
Public Member Functions inherited from NormalizedSource
void	launch (PhotonPacket *pp, size_t historyIndex, double L) const override
virtual void	launchNormalized (PhotonPacket *pp, size_t historyIndex, double lambda, double Lw) const =0
double	luminosity () const override
LuminosityNormalization *	normalization () const
SED *	sed () const
double	specificLuminosity (double wavelength) const override
Range	wavelengthRange () const override
Public Member Functions inherited from Source
virtual int	dimension () const =0
virtual bool	hasVelocity () const =0
virtual void	launch (PhotonPacket *pp, size_t historyIndex, double L) const =0
virtual double	luminosity () const =0
virtual void	prepareForLaunch (double sourceBias, size_t firstIndex, size_t numIndices)
double	sourceWeight () const
virtual double	specificLuminosity (double wavelength) const =0
double	wavelengthBias () const
WavelengthDistribution *	wavelengthBiasDistribution () 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
Public Member Functions inherited from WavelengthRangeInterface
virtual	~WavelengthRangeInterface ()
virtual Range	wavelengthRange () const =0
Public Member Functions inherited from VelocityInterface
virtual	~VelocityInterface ()
virtual Vec	velocity () const =0

Protected Member Functions
	StellarSurfaceSource ()
Protected Member Functions inherited from CenteredSource
	CenteredSource ()
Protected Member Functions inherited from SpecialtySource
	SpecialtySource ()
void	setupSelfBefore () override
Protected Member Functions inherited from NormalizedSource
	NormalizedSource ()
void	setupSelfAfter () override
void	setupSelfBefore () override
Protected Member Functions inherited from Source
	Source ()
void	informAvailableWavelengthRange (Range available, string itemType)
Random *	random () const
void	setupSelfBefore () override
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 ()
Protected Member Functions inherited from SourceWavelengthRangeInterface
	SourceWavelengthRangeInterface ()
Protected Member Functions inherited from WavelengthRangeInterface
	WavelengthRangeInterface ()
Protected Member Functions inherited from VelocityInterface
	VelocityInterface ()

Private Types
using	BaseType = CenteredSource
using	ItemType = StellarSurfaceSource

Private Attributes
double	_stellarRadius

Friends
class	ItemRegistry

Detailed Description

The StellarSurfaceSource class represents the surface of a sphere of radius $r_{\ast }$ from which radiation escapes in the outward direction. The emissivity of this source is anisotropic. There is no radiation inwards and the intensity is proportional to $\cos {\theta }^{\prime }$ in the outward hemisphere, where ${\theta }^{\prime }$ is the angle between the direction and the normal on the surface.

Constructor & Destructor Documentation

StellarSurfaceSource()

StellarSurfaceSource::StellarSurfaceSource ( )

inlineprotected

Default constructor for concrete Item subclass StellarSurfaceSource : "a stellar surface source with an anisotropic outward radiation field" .

Member Function Documentation

intrinsicDimension()

int StellarSurfaceSource::intrinsicDimension ( ) const

overridevirtual

This function returns the intrinsic dimension of the geometry, which is 1 in this case: the geometry is spherically symmetric, even with the anisotropic emissivity.

Implements CenteredSource.

launchSpecialty()

void StellarSurfaceSource::launchSpecialty ( PhotonPacket *  pp, size_t  historyIndex, double  lambda, double  Lw, VelocityInterface *  bvi  ) const

overridevirtual

This function causes the photon packet pp to be launched from the source using the given history index, wavelength, weighted luminosity contribution, and redshift interface (corresponding to the bulk velocity of the source).

Firstly, the function generates a random outward launch position $\mathbf{r}$ on the stellar surface by drawing a random direction $\mathbf{u}$ on the unit sphere and transforming it to take into account the stellar radius and center position. The direction $\mathbf{u}$ actually corresponds to the outward normal to the stellar surface at the position $\mathbf{r}$.

Secondly, the function generates a random direction $\mathbf{k}$ appropriate for the anisotropic outward radiation field at the location $\mathbf{r}$, or equivalently, for the normal $\mathbf{u}$. In a spherical coordinate system with the Z' axis along the normal $\mathbf{u}$, the probability distribution is given by

$$p({\theta }^{\prime },{\phi }^{\prime })\text{d}{\theta }^{\prime }\text{d}{\phi }^{\prime }=\frac{1}{\pi }\cos {\theta }^{\prime }\sin {\theta }^{\prime }\text{d}{\theta }^{\prime }\text{d}{\phi }^{\prime }0\le {\theta }^{\prime }<\frac{\pi }{2}.$$

Random angles ${\theta }^{\prime }$ and ${\phi }^{\prime }$ can be determined by taking two uniform deviates ${\mathcal{X}}_1$ and ${\mathcal{X}}_2$ and solving the two equations

$$\begin{array}{rl}{\mathcal{X}}_1& ={\int }_0^{{\theta }^{\prime }}2\sin {\theta }^{\mathrm{\prime }\mathrm{\prime }}\cos {\theta }^{\mathrm{\prime }\mathrm{\prime }}\text{d}{\theta }^{\mathrm{\prime }\mathrm{\prime }}\\ {\mathcal{X}}_2& ={\int }_0^{{\phi }^{\prime }}\frac{\text{d}{\phi }^{\mathrm{\prime }\mathrm{\prime }}}{2\pi }\end{array}$$

for ${\theta }^{\prime }$ and ${\phi }^{\prime }$. The solution is readily found,

$$\begin{array}{rl}{\theta }^{\prime }& =\arcsin \sqrt{{\mathcal{X}}_1}\\ {\phi }^{\prime }& =2\pi {\mathcal{X}}_2.\end{array}$$

Once these values have been determined, we need to determine the coordinates of the vector $\mathbf{k}$ in the standard coordinate system. The link between the standard XYZ coordinate system and the one with the Z' axis determined by the normal $\mathbf{u}$ is a joint rotation over an angle $\phi$ along the Z-axis, followed by a rotation over an angle $\theta$ over the Y'-axis, where $\theta$ and $\phi$ are the polar angle and azimuth of the position vector $\mathbf{r}$. The connection is hence

$$\left[\begin{array}{c}{k}_x^{\prime }\\ k_y^{\prime }\\ k_z^{\prime }\end{array}\right]=\left[\begin{array}{ccc}\cos \theta & 0& -\sin \theta \\ 0& 1& 0\\ \sin \theta & 0& \cos \theta \end{array}\right]\left[\begin{array}{ccc}\cos \varphi & \sin \varphi & 0\\ -\sin \varphi & \cos \varphi & 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{c}{k}_x\\ k_y\\ k_z\end{array}\right]$$

or in the other direction

$$\left[\begin{array}{c}{k}_x\\ k_y\\ k_z\end{array}\right]=\left[\begin{array}{ccc}\cos \varphi & -\sin \varphi & 0\\ \sin \varphi & \cos \varphi & 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{ccc}\cos \theta & 0& \sin \theta \\ 0& 1& 0\\ -\sin \theta & 0& \cos \theta \end{array}\right]\left[\begin{array}{c}{k}_x^{\prime }\\ k_y^{\prime }\\ k_z^{\prime }\end{array}\right]$$

Thirdly, the function sets up a thread-local object that serves the angular distribution interface for a particular launch position. Configured with the appropriate launch position $\mathbf{u}$, this object is handed to the photon packet being launched so that peel-off photon packets can retrieve the appropriate bias factor for the instrument direction. This works even if there are multiple sources of this type because each thread handles a single photon packet at a time.

The local angular distribution object implements a function that returns the normalized probability for a direction $\mathbf{k}$, given that the point of emission is defined by the normal $\mathbf{u}$. The appropriate probability distribution is given by

$$p(\mathbf{k})\text{d}\mathrm{\Omega }=\{\begin{array}{ll}4\cos {\theta }^{\prime }\text{d}\mathrm{\Omega }& 0\le {\theta }^{\prime }<\frac{\pi }{2}\\ 0& \frac{\pi }{2}\le {\theta }^{\prime }<\pi \end{array}$$

Here ${\theta }^{\prime }$ is the angle between the direction $\mathbf{k}$ and the outward normal $\mathbf{u}$ on the stellar surface, i.e.

$$\cos {\theta }^{\prime }=\mathbf{k}\cdot \mathbf{r}.$$

This distribution is correctly normalized in the sense that

$$\frac{1}{4\pi }\iint p(\mathbf{k})\text{d}\mathrm{\Omega }=1.$$

Finally, the function launches the photon packet, passing it all of the above information.

Implements SpecialtySource.

stellarRadius()

StellarSurfaceSource::stellarRadius ( ) const

inline

This function returns the value of the discoverable double property stellarRadius : "the stellar radius" .

This property represents a physical quantity of type "length" .

The minimum value for this property is "]0" .

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

• StellarSurfaceSource.hpp