SpinFlipAbsorptionMix Class Reference

#include <SpinFlipAbsorptionMix.hpp>

Inheritance diagram for SpinFlipAbsorptionMix:

Public Member Functions
double	defaultTemperature () const
bool	hasExtraSpecificState () const override
double	indicativeTemperature (const MaterialState *state, const Array &Jv) const override
void	initializeSpecificState (MaterialState *state, double metallicity, double temperature, const Array &params) const override
double	mass () const override
MaterialType	materialType () const override
double	opacityAbs (double lambda, const MaterialState *state, const PhotonPacket *pp) const override
double	opacityExt (double lambda, const MaterialState *state, const PhotonPacket *pp) const override
double	opacitySca (double lambda, const MaterialState *state, const PhotonPacket *pp) const override
void	peeloffScattering (double &I, double &Q, double &U, double &V, double &lambda, Direction bfkobs, Direction bfky, const MaterialState *state, const PhotonPacket *pp) const override
void	performScattering (double lambda, const MaterialState *state, PhotonPacket *pp) const override
double	sectionAbs (double lambda) const override
double	sectionExt (double lambda) const override
double	sectionSca (double lambda) const override
vector< StateVariable >	specificStateVariableInfo () const override
Public Member Functions inherited from MaterialMix
virtual double	asymmpar (double lambda) const
virtual Array	emissionSpectrum (const MaterialState *state, const Array &Jv) const
virtual DisjointWavelengthGrid *	emissionWavelengthGrid () const
virtual Array	emissivity (const Array &Jv) const
virtual bool	hasContinuumEmission () const
virtual DynamicStateType	hasDynamicMediumState () const
virtual bool	hasExtraSpecificState () const
virtual bool	hasLineEmission () const
virtual bool	hasNegativeExtinction () const
virtual bool	hasPolarizedAbsorption () const
virtual bool	hasPolarizedEmission () const
virtual bool	hasPolarizedScattering () const
virtual bool	hasResonantScattering () const
virtual bool	hasScatteringDispersion () const
virtual bool	hasStochasticDustEmission () const
virtual double	indicativeTemperature (const MaterialState *state, const Array &Jv) const
virtual void	initializeSpecificState (MaterialState *state, double metallicity, double temperature, const Array &params) const
bool	isDust () const
bool	isElectrons () const
bool	isGas () const
virtual bool	isSpecificStateConverged (int numCells, int numUpdated, int numNotConverged, MaterialState *currentAggregate, MaterialState *previousAggregate) const
virtual Array	lineEmissionCenters () const
virtual Array	lineEmissionMasses () const
virtual Array	lineEmissionSpectrum (const MaterialState *state, const Array &Jv) const
virtual double	mass () const =0
virtual MaterialType	materialType () const =0
virtual double	opacityAbs (double lambda, const MaterialState *state, const PhotonPacket *pp) const =0
virtual double	opacityExt (double lambda, const MaterialState *state, const PhotonPacket *pp) const =0
virtual double	opacitySca (double lambda, const MaterialState *state, const PhotonPacket *pp) const =0
virtual vector< SnapshotParameter >	parameterInfo () const
virtual void	peeloffScattering (double &I, double &Q, double &U, double &V, double &lambda, Direction bfkobs, Direction bfky, const MaterialState *state, const PhotonPacket *pp) const =0
virtual void	performScattering (double lambda, const MaterialState *state, PhotonPacket *pp) const =0
virtual double	sectionAbs (double lambda) const =0
virtual double	sectionExt (double lambda) const =0
virtual const Array &	sectionsAbs (double lambda) const
virtual const Array &	sectionsAbspol (double lambda) const
virtual double	sectionSca (double lambda) const =0
virtual vector< StateVariable >	specificStateVariableInfo () const =0
virtual const Array &	thetaGrid () const
virtual UpdateStatus	updateSpecificState (MaterialState *state, const Array &Jv) 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
	SpinFlipAbsorptionMix ()
Protected Member Functions inherited from MaterialMix
	MaterialMix ()
Configuration *	config () const
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 ()

Private Types
using	BaseType = MaterialMix
using	ItemType = SpinFlipAbsorptionMix

Private Attributes
double	_defaultTemperature

Friends
class	ItemRegistry

Additional Inherited Members
Public Types inherited from MaterialMix
enum class	DynamicStateType { None , Primary , Secondary , PrimaryIfMergedIterations }
enum class	MaterialType { Dust , Electrons , Gas }

Detailed Description

The SpinFlipAbsorptionMix class describes the material properties related to the 21 cm spin-flip transition in neutral atomic hydrogen, including only absorption (i.e. omitting emission processes). The 21 cm opacity in a given cell is determined from gas properties defined in the input model (gas temperature).

Configuring the simulation

Simulations of 21 cm the spin-flip transition usually include 21 cm emission (see the SpinFlipSEDFamily class) in addition to a medium component configured with the spin flip material mix (this class). Hence, the simulation mode should be set to "ExtinctionOnly".

As the opacity of the 21 cm line depends on the gas temperature as well as the neutral atomic hydrogen density $n_{\mathrm{H}\mathrm{I}}$, this information is read from an input file by associating the SpinFlipAbsorptionMix with a subclass of ImportedMedium. For that medium component, the ski file attribute importTemperature must be set to 'true', and importMetallicity and importVariableMixParams must be left at 'false'. For example, if bulk velocities are also imported for this medium component (i.e. importVelocity is 'true'), the column order would be

$$...,T,v_{\mathrm{x}},v_{\mathrm{y}},v_{\mathrm{z}}$$

For basic testing purposes, the SpinFlipAbsorptionMix can also be associated with a geometric medium component. The geometry then defines the spatial density distribution (i.e. $n_{\mathrm{H}\mathrm{I}}$), and this class offers a configuration property to specify a fixed default temperature value that will be used across the spatial domain.

Absorption

Following Draine 2011 Chapter 8, and substituting wavelengths for frequencies, the monochromatic absorption cross section per neutral hydrogen atom $\varsigma (\lambda )$ at frequency $\lambda$ can be written as

$${\varsigma }^{\text{abs}}(\lambda )=\frac{3}{32\pi }{A}_{\mathrm{S}\mathrm{F}}\frac{hc{\lambda }_{\mathrm{S}\mathrm{F}}}{k_{\mathrm{B}}{T}_{\mathrm{s}}}\times \frac{{\lambda }_{\mathrm{S}\mathrm{F}}}{\sqrt{2\pi }\sigma }\exp (-\frac{u^2(\lambda )}{2{\sigma }^2})$$

where $T_{\mathrm{s}}$ is the spin temperature of the hydrogen gas (see below), $\sigma =\sqrt{k_{B}T/m_{\mathrm{p}}}$ is the velocity dispersion corresponding to the thermal motion of the atoms, and $u(\lambda )=c(\lambda -{\lambda }_{\mathrm{S}\mathrm{F}})/\lambda$ is the frequency deviation from the line center in velocity units.

According to Kim, Ostriker and Kim 2014 (ApJ 786:64), the spin temperature $T_{\mathrm{s}}$ is essentially equal to the kinetic gas temperature $T$ for low gas temperatures $T<1000\mathrm{K}$. For higher gas temperatures, it also depends on other gas properties, with an upper bound that never exceeds a fixed maximum value, i.e. $T_{\mathrm{s},\mathrm{u}\mathrm{p}\mathrm{p}\mathrm{e}\mathrm{r}}\lesssim 5000\mathrm{K}$ (see their Figure 2).

To avoid the need for defining additional gas properties in the input model, we here use an approximate upper bound for the spin temperature given by

$$T_{\mathrm{s}}=6000\mathrm{K}\times (1-{\mathrm{e}}^{-T/5000\mathrm{K}}).$$

Because the absorption cross section is inversely proportional to the spin temperature, this yields an approximate lower bound for the cross section.

Constructor & Destructor Documentation

SpinFlipAbsorptionMix()

SpinFlipAbsorptionMix::SpinFlipAbsorptionMix ( )

inlineprotected

Default constructor for concrete Item subclass SpinFlipAbsorptionMix : "A gas mix supporting the spin-flip 21 cm hydrogen absorption" .

Member Function Documentation

defaultTemperature()

SpinFlipAbsorptionMix::defaultTemperature ( ) const

inline

This function returns the value of the discoverable double property defaultTemperature : "the default temperature of the gas" .

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

The minimum value for this property is "[3" .

The maximum value for this property is "1e9]" .

The default value for this property is given by the conditional value expression "1e4" .

This property is displayed only if the Boolean expression "Level2" evaluates to true after replacing the names by true or false depending on their presence.

hasExtraSpecificState()

bool SpinFlipAbsorptionMix::hasExtraSpecificState ( ) const

overridevirtual

This function returns true, indicating that the cross sections returned by this material mix depend on the values of specific state variables other than the number density.

Reimplemented from MaterialMix.

indicativeTemperature()

double SpinFlipAbsorptionMix::indicativeTemperature ( const MaterialState *  state, const Array &  Jv  ) const

overridevirtual

This function returns an indicative temperature of the material mix when it would be embedded in a given radiation field. The implementation in this class ignores the radiation field and returns the temperature stored in the specific state for the relevant spatial cell and medium component. Because the hydrogen temperature is not calculated self-consistently in our treatment, this value corresponds to the temperature defined by the input model at the start of the simulation.

Reimplemented from MaterialMix.

initializeSpecificState()

void SpinFlipAbsorptionMix::initializeSpecificState ( MaterialState *  state, double  metallicity, double  temperature, const Array &  params  ) const

overridevirtual

This function initializes the specific state variables requested by this material mix through the specificStateVariableInfo() function except for the number density. For this class, the function initializes the temperature to the specified imported value, or if not available, to the user-configured default value.

Reimplemented from MaterialMix.

mass()

double SpinFlipAbsorptionMix::mass ( ) const

overridevirtual

This function returns the mass of a neutral hydrogen atom.

Implements MaterialMix.

materialType()

MaterialType SpinFlipAbsorptionMix::materialType ( ) const

overridevirtual

This function returns the fundamental material type represented by this material mix, which is MaterialType::Gas.

Implements MaterialMix.

opacityAbs()

double SpinFlipAbsorptionMix::opacityAbs ( double  lambda, const MaterialState *  state, const PhotonPacket *  pp  ) const

overridevirtual

This function returns the 21 cm absorption opacity $k^{\text{abs}}=n_{m}athrmHI{\varsigma }^{\text{abs}}$ for the given wavelength and material state. The photon packet properties are not used.

Implements MaterialMix.

opacityExt()

double SpinFlipAbsorptionMix::opacityExt ( double  lambda, const MaterialState *  state, const PhotonPacket *  pp  ) const

overridevirtual

This function returns the 21 cm extinction opacity $k^{\text{ext}}=k^{\text{abs}}$ for the given wavelength and material state, which equals the absorption opacity because the scattering opacity is zero. The photon packet properties are not used.

Implements MaterialMix.

opacitySca()

double SpinFlipAbsorptionMix::opacitySca ( double  lambda, const MaterialState *  state, const PhotonPacket *  pp  ) const

overridevirtual

This function returns the 21 cm scattering opacity $k^{\text{sca}}$ which is trivially zero at all wavelengths.

Implements MaterialMix.

peeloffScattering()

void SpinFlipAbsorptionMix::peeloffScattering ( double &  I, double &  Q, double &  U, double &  V, double &  lambda, Direction  bfkobs, Direction  bfky, const MaterialState *  state, const PhotonPacket *  pp  ) const

overridevirtual

This function does nothing because the 21 cm line does not scatter.

Implements MaterialMix.

performScattering()

void SpinFlipAbsorptionMix::performScattering ( double  lambda, const MaterialState *  state, PhotonPacket *  pp  ) const

overridevirtual

This function does nothing because the 21 cm line does not scatter.

Implements MaterialMix.

sectionAbs()

double SpinFlipAbsorptionMix::sectionAbs ( double  lambda ) const

overridevirtual

This function returns the 21 cm absorption cross section per neutral hydrogen atom at the given wavelength and using the default gas properties configured for this material mix.

Implements MaterialMix.

sectionExt()

double SpinFlipAbsorptionMix::sectionExt ( double  lambda ) const

overridevirtual

This function returns the total 21 cm extinction cross section per neutral hydrogen atom at the given wavelength and using the default gas properties configured for this material mix. The extinction cross section is identical to the absorption cross section because the scattering cross section is zero.

Implements MaterialMix.

sectionSca()

double SpinFlipAbsorptionMix::sectionSca ( double  lambda ) const

overridevirtual

This function returns the 21 scattering cross section per neutral hydrogen atom, which is trivially zero for all wavelengths.

Implements MaterialMix.

specificStateVariableInfo()

vector< StateVariable > SpinFlipAbsorptionMix::specificStateVariableInfo ( ) const

overridevirtual

This function returns a list of StateVariable objects describing the specific state variables used by the receiving material mix. For this class, the function returns a list containing descriptors for the properties defined in the input model, namely number density and temperature.

Implements MaterialMix.

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

• SpinFlipAbsorptionMix.hpp