SpinFlipHydrogenGasMix Class Reference

#include <SpinFlipHydrogenGasMix.hpp>

Inheritance diagram for SpinFlipHydrogenGasMix:

Public Member Functions
double	defaultMetallicity () const
double	defaultNeutralSurfaceDensity () const
double	defaultTemperature () const
DynamicStateType	hasDynamicMediumState () const override
bool	hasExtraSpecificState () const override
bool	hasLineEmission () 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
Array	lineEmissionCenters () const override
Array	lineEmissionMasses () const override
Array	lineEmissionSpectrum (const MaterialState *state, const Array &Jv) const override
double	mass () 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
vector< SnapshotParameter >	parameterInfo () 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
UpdateStatus	updateSpecificState (MaterialState *state, const Array &Jv) const override
Public Member Functions inherited from EmittingGasMix
MaterialType	materialType () const override
double	sourceWeight () const
double	wavelengthBias () const
WavelengthDistribution *	wavelengthBiasDistribution () const
Range	wavelengthRange () 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
Public Member Functions inherited from WavelengthRangeInterface
virtual	~WavelengthRangeInterface ()
virtual Range	wavelengthRange () const =0

Protected Member Functions
	SpinFlipHydrogenGasMix ()
void	setupSelfBefore () override
Protected Member Functions inherited from EmittingGasMix
	EmittingGasMix ()
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 ()
Protected Member Functions inherited from SourceWavelengthRangeInterface
	SourceWavelengthRangeInterface ()
Protected Member Functions inherited from WavelengthRangeInterface
	WavelengthRangeInterface ()

Private Types
using	BaseType = EmittingGasMix
using	ItemType = SpinFlipHydrogenGasMix

Private Attributes
double	_defaultMetallicity
double	_defaultNeutralSurfaceDensity
double	_defaultTemperature
int	_indexUV

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 SpinFlipHydrogenGasMix class describes the material properties related to the 21 cm spin-flip transition in neutral atomic hydrogen, including emission and absorption. The 21 cm emission luminosity and self-absorption opacity in a given cell are determined from gas properties defined in the input model (neutral hydrogen volume density, gas metallity, gas temperature, and neutral hydrogen surface density) and the local UV radiation field calculated by the simulation taking into account dust extinction.

Configuring the simulation

Simulations of the 21 cm the spin-flip transition usually include primary sources and a dust medium in addition to a medium component configured with the spin flip material mix (this class). During primary emission, the dust medium determines the UV radiation field, allowing the spin flip material mix to calculate the 21 cm line luminosity and absorption cross section for use during secondary emission. This calculation happens in the updateSpecificState() function, which is invoked at the end of primary emission (because the material mix advertises that it has a secondary dynamic medium state). This does imply that the 21 cm line absorption remains zero during primary emission, which is not a problem as long as the primary sources don't emit in the radio wavelength range. Thus, unless dust opacities are very high, there is no need for iteration over primary nor secondary emission.

If one is not interested in dust emission (i.e. only in the 21 cm line emission), the simulation mode can be set to "GasEmission" and the radiation field wavelength grid can be limited to a single bin in the UV wavelength range. This bin should be configured to cover the full Lyman-Werner band (912-1110 Å) so that it accurately captures all radiation that dissociates molecular hydrogen. Similarly, instrument wavelength grids can be limited to a relevant range around the 21 cm line center.

To calculate both the dust emission spectrum and the 21 cm line emission in the same simulation, the simulation mode must be set to "DustAndGasEmission" and the radiation field wavelength grid must now include and properly resolve the UV, optical, and infrared wavelength range. Separate instruments can be configured for the relevant wavelength ranges, e.g. using a logarithmic grid for the continuum spectrum and a linear grid for the 21 cm line profile.

The input model must provide values for the spatial distribution of four medium properties that remain constant during the simulation:

• The neutral hydrogen volume number density $n_{\mathrm{H}\mathrm{I}+\mathrm{H}2}=n_{\mathrm{H}\mathrm{I}}+2n_{\mathrm{H}2}$, i.e. including non-ionized atomic and molecular hydrogen. Note the factor 2 in this equation; $n_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$ specifies the number of protons rather than the number of hydrogen-like particles.
• The metallicity $Z$ of the gas.
• The kinetic temperature $T$ of the gas.
• The neutral hydrogen surface mass density ${\mathrm{\Sigma }}_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$, required by the scheme that partitions the neutral hydrogen into atomic and molecular fractions (see below).

Most often, this information will be read from an input file by associating the spin flip material mix with a subclass of ImportedMedium. For that medium component, the ski file attributes importMetallicity and importTemperature must be set to 'true', and importVariableMixParams must be left at 'false'. The additional column required by the spin flip material mix (neutral hydrogen surface mass density) is automatically imported and is expected after all other columns. For example, if bulk velocities are also imported for this medium component (i.e. importVelocity is 'true'), the column order would be

$$...,n_{\mathrm{H}\mathrm{I}+\mathrm{H}2},Z,T,v_{\mathrm{x}},v_{\mathrm{y}},v_{\mathrm{z}},{\mathrm{\Sigma }}_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$$

Depending on the specific ImportedMedium subclass being used, the neutral hydrogen density distribution in the first column can be specified as a mass or number density, or as a volume-integrated mass or number for each cell or particle. In all cases, the value is automatically converted to the appropriate volume number density expected by this class. In contrast, the neutral hydrogen surface density must always be specified as a surface mass density, with default units of Msun/pc2.

Note

It is customary to obtain ${\mathrm{\Sigma }}_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$ by multiplying $n_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$ with a specific length scale (and converting from number to mass density). Some authors use the Sobolev length, but most use the Jeans length. The Jeans length can be easily computed from the gas cell data (gas mass density, internal energy, hydrogen mass fraction, and electron fraction). This rough approximation broadly matches the interpretation of surface density in the partitioning scheme used by this class (see below).

For basic testing purposes, the spin flip material mix can also be associated with a geometric medium component. The geometry then defines the spatial neutral hydrogen density distribution (i.e. $n_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$), and the spin flip material mix offers configuration properties to specify fixed default values for the other properties that will be used across the spatial domain.

Partitioning scheme

While the input model defines the neutral (i.e. non-ionized) hydrogen density distribution, the partitioning of the hydrogen gas into its atomic and molecular components must be determined based on the the UV radiation field calculated by the simulation. Since UV radiation in the Lyman-Werner band (912-1110 Å) dissociates molecular hydrogen, a hydrogen partitioning scheme usually has the UV field in that wavelength range as an important parameter. For this purpose, this class samples the radiation field $J_{\lambda }({\lambda }_{\mathrm{U}\mathrm{V}})$ at ${\lambda }_{\mathrm{U}\mathrm{V}}=1000\AA$. The wavelength bin index for ${\lambda }_{\mathrm{U}\mathrm{V}}$ in the radiation field grid is determined during setup.

This class implements the column-density based partioning scheme of Gnedin & Draine 2014 (Apj, 795, 37), which is an update of Gnedin & Kravtsov 2011 (ApJ, 728, 88). The mechanism for estimating the length scale of a gas cell is taken from Diemer et al. 2018 (ApJS, 238, 33).

The scheme has the following input parameters:

• The neutral hydrogen surface mass density ${\mathrm{\Sigma }}_{\mathrm{H}\mathrm{I}+\mathrm{H}2}$ defined in the input model.
• The dust-to-gas ratio $D_{\mathrm{M}\mathrm{W}}$ relative to the representative Milky Way value. Because the dust-to-gas ratio can be assumed to scale with metallicity, this is roughly equivalent to the gas metallicity relative to the solar value. In other words, $D_{\mathrm{M}\mathrm{W}}=Z/0.0127$, where $Z$ is the metallicity defined in the input model.
• The dimensionless UV radiation field $U_{\mathrm{M}\mathrm{W}}=J_{\lambda }({\lambda }_{\mathrm{U}\mathrm{V}})/J_{\lambda }^{\mathrm{M}\mathrm{W}}({\lambda }_{\mathrm{U}\mathrm{V}})$, obtained by normalizing the sampled UV radiation field to the representative Milky Way value, which is taken to be $J_E^{\mathrm{M}\mathrm{W}}({\lambda }_{\mathrm{U}\mathrm{V}})={10}^6\mathrm{p}\mathrm{h}\mathrm{o}\mathrm{t}\mathrm{o}\mathrm{n}\mathrm{s}{\mathrm{c}\mathrm{m}}^{-2}{\mathrm{s}}^{-1}{\mathrm{s}\mathrm{r}}^{-1}{\mathrm{e}\mathrm{V}}^{-1}$. The latter value is converted at compile time from the specified photons-per-energy cgs units to the internal SKIRT energy-per-wavelength SI units using

  $$J_{\lambda }^{\mathrm{M}\mathrm{W}}({\lambda }_{\mathrm{U}\mathrm{V}})={10}^4\frac{(hc{)}^2}{q_{\mathrm{e}\mathrm{l}}{\lambda }_{\mathrm{U}\mathrm{V}}^3}{J}_E^{\mathrm{M}\mathrm{W}}({\lambda }_{\mathrm{U}\mathrm{V}}).$$

• The length scale $L_{\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}}$, introduced to obtain converged results when applying the partitioning scheme to simulations of varying resolutions. An estimate for this value is obtained using $L_{\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}}=V_{\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}}^{1/3}$, where $V_{\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}}$ denotes the volume of the spatial grid cell under consideration.

With these input parameters, the partitioning scheme can be summarized as follows:

$$S=L_{\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}}/100\mathrm{p}\mathrm{c}$$

$$D_{\ast }=0.17\frac{2+S^5}{1+S^5}$$

$$g=\sqrt{D_{\mathrm{M}\mathrm{W}}^2+D_{\ast }^2}$$

$${\mathrm{\Sigma }}_c=5\times {10}^7{\mathrm{M}}_{\odot }{\mathrm{k}\mathrm{p}\mathrm{c}}^{-2}\times (\frac{\sqrt{0.001+0.1U_{\mathrm{M}\mathrm{W}}}}{g(1+1.69\sqrt{0.001+0.1U_{\mathrm{M}\mathrm{W}}}})$$

$$\alpha =0.5+\frac{1}{1+\sqrt{U_{\mathrm{M}\mathrm{W}}{D}_{\mathrm{M}\mathrm{W}}^2/600}}$$

$$R_{\mathrm{m}\mathrm{o}\mathrm{l}}=(\frac{{\mathrm{\Sigma }}_{\mathrm{H}\mathrm{I}+{\mathrm{H}}_2}}{{\mathrm{\Sigma }}_c}{)}^{\alpha }$$

$$f_{\mathrm{m}\mathrm{o}\mathrm{l}}=\frac{R_{\mathrm{m}\mathrm{o}\mathrm{l}}}{R_{\mathrm{m}\mathrm{o}\mathrm{l}}+1}$$

where $f_{\mathrm{m}\mathrm{o}\mathrm{l}}$ is the fraction of molecular hydrogen in the neutral hydrogen gas, and $f_{\mathrm{a}\mathrm{t}\mathrm{o}\mathrm{m}}=1-f_{\mathrm{m}\mathrm{o}\mathrm{l}}$ is the corresponding atomic hydrogen fraction.

Emission

Following Draine 2011 Chapter 8, the integrated luminosity $L$ of the 21 cm line for a given spatial cell can be written as

$$L=\frac{3}{4}{A}_{\mathrm{S}\mathrm{F}}\frac{hc}{{\lambda }_{\mathrm{S}\mathrm{F}}}{n}_{\mathrm{H}\mathrm{I}}V$$

where $A_{\mathrm{S}\mathrm{F}}=2.8843\times {10}^{-15}{s}^{-1}$ is the Einstein coefficient of the 21cm spin-flip transition, ${\lambda }_{\mathrm{S}\mathrm{F}}=21.10611405413\times {10}^{-2}\mathrm{m}$ is its wavelength, $n_{\mathrm{H}\mathrm{I}}$ is the number density of atomic hydrogen in the cell, and $V$ is the cell volume.

The 21 cm line is extremely narrow so that the emerging line profile is dominated by the Doppler shift caused by the thermal motion of the atoms. The gas temperature defined in the input model is used to randomly shift the wavelength of each emitted photon packet according to a Maxwell-Boltzmann distribution. This happens outside of this class in the secondary source machinery.

Absorption

Again 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.

When an item of this type is used, the names provided by the conditional value expression "CustomMediumState,DynamicState" are inserted into the name sets used for evaluating Boolean expressions.

Constructor & Destructor Documentation

SpinFlipHydrogenGasMix()

SpinFlipHydrogenGasMix::SpinFlipHydrogenGasMix ( )

inlineprotected

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

Member Function Documentation

defaultMetallicity()

SpinFlipHydrogenGasMix::defaultMetallicity ( ) const

inline

This function returns the value of the discoverable double property defaultMetallicity : "the default metallicity of the gas" .

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

The maximum value for this property is "0.2]" .

The default value for this property is given by the conditional value expression "0.02" .

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.

defaultNeutralSurfaceDensity()

SpinFlipHydrogenGasMix::defaultNeutralSurfaceDensity ( ) const

inline

This function returns the value of the discoverable double property defaultNeutralSurfaceDensity : "the default neutral hydrogen surface density" .

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

The minimum value for this property is "]0 Msun/pc2" .

The maximum value for this property is "1e9 Msun/pc2]" .

The default value for this property is given by the conditional value expression "10 Msun/pc2" .

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.

defaultTemperature()

SpinFlipHydrogenGasMix::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.

hasDynamicMediumState()

DynamicStateType SpinFlipHydrogenGasMix::hasDynamicMediumState ( ) const

overridevirtual

This function returns DynamicStateType::Secondary, indicating that this material mix has a dynamic medium state with updates that affect only secondary emission.

Reimplemented from MaterialMix.

hasExtraSpecificState()

bool SpinFlipHydrogenGasMix::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.

hasLineEmission()

bool SpinFlipHydrogenGasMix::hasLineEmission ( ) const

overridevirtual

This function returns true, indicating that this material supports secondary line emission from gas.

Reimplemented from MaterialMix.

indicativeTemperature()

double SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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, metallicity and neutral hydrogen mass surface density to the specified imported values, or if not available, to the user-configured default values. The atomic hydrogen fraction is set to zero.

Reimplemented from MaterialMix.

lineEmissionCenters()

Array SpinFlipHydrogenGasMix::lineEmissionCenters ( ) const

overridevirtual

This function returns a list including a single item: the line center of the 21 cm hydrogen spinflip transition.

Reimplemented from MaterialMix.

lineEmissionMasses()

Array SpinFlipHydrogenGasMix::lineEmissionMasses ( ) const

overridevirtual

This function returns a list including a single item: the mass of the particle emitting the 21 cm line, i.e. the hydrogen atom.

Reimplemented from MaterialMix.

lineEmissionSpectrum()

Array SpinFlipHydrogenGasMix::lineEmissionSpectrum ( const MaterialState *  state, const Array &  Jv  ) const

overridevirtual

This function returns a list including a single item: the 21 cm line luminosity in the spatial cell and medium component represented by the specified material state and the receiving material mix when it would be embedded in the specified radiation field.

Reimplemented from MaterialMix.

mass()

double SpinFlipHydrogenGasMix::mass ( ) const

overridevirtual

This function returns the mass of a neutral hydrogen atom.

Implements MaterialMix.

opacityAbs()

double SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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.

parameterInfo()

vector< SnapshotParameter > SpinFlipHydrogenGasMix::parameterInfo ( ) const

overridevirtual

This function returns the number and type of import parameters required by this particular material mix as a list of SnapshotParameter objects. For this class, the function returns a descriptor for the neutral hydrogen mass surface density import parameter. Importing metallicity and temperature should be enabled through the corresponding standard configuration flags.

Reimplemented from MaterialMix.

peeloffScattering()

void SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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 SpinFlipHydrogenGasMix::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.

setupSelfBefore()

void SpinFlipHydrogenGasMix::setupSelfBefore ( )

overrideprotectedvirtual

This function determines the radiation field wavelength bin containing the UV field strength.

Reimplemented from MaterialMix.

specificStateVariableInfo()

vector< StateVariable > SpinFlipHydrogenGasMix::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 (neutral hydrogen number density, metallicity, temperature, and neutral hydrogen mass surface density) and for a variable to hold the atomic hydrogen fraction derived from the radiation field when the dynamic medium state is updated.

Implements MaterialMix.

updateSpecificState()

UpdateStatus SpinFlipHydrogenGasMix::updateSpecificState ( MaterialState *  state, const Array &  Jv  ) const

overridevirtual

Based on the specified radiation field and the input model properties found in the given material state, this function performs the partitioning scheme described in the class header and stores the resulting atomic hydrogen fraction back in the given material state. The function returns the update status as described for the UpdateStatus class.

Reimplemented from MaterialMix.

---

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

• SpinFlipHydrogenGasMix.hpp