synthesizer.conversions

A module containing functions for conversions.

This module contains helpful conversions for converting between different observables. This mainly covers conversions between flux, luminosity and magnitude systems.

Example usage:

lum = flux_to_luminosity(flux, cosmo, redshift) fnu = apparent_mag_to_fnu(m) lnu = absolute_mag_to_lnu(M)

Functions

synthesizer.conversions.absolute_mag_to_lnu(ab_mag)

Convert absolute magnitude (M) to luminosity.

The conversion is done using the formula:

L_nu = 10**(-0.4 * (M + 48.6)) * dist_mod

The result will be in units of erg / s / Hz.

Parameters:

ab_mag (float) – The absolute magnitude to convert.

Returns:

unyt_quantity/unyt_array

The luminosity in erg / s / Hz.

synthesizer.conversions.air_to_vacuum(wavelength)

Convert an air wavelength into a vacuum wavelength.

Arguments

wavelength (float or unyt_array)

A standard wavelength.

Returns

wavelength (unyt_array)

A wavelength in vacuum.

synthesizer.conversions.angular_to_spatial_at_z(angular, cosmo, redshift)

Convert angular distance to spatial distance at a specified redshift.

Parameters:

• angular (unyt_quantity) – The angular distance to convert.

• cosmo (astropy.cosmology) – The cosmology object used to calculate angular diameter distance.

• redshift (float) – The redshift of the source.

Returns:

unyt_quantity

The converted spatial distance in kpc.

synthesizer.conversions.apparent_mag_to_fnu(app_mag)

Convert apparent AB magnitude to flux.

The conversion is done using the formula:

F_nu = 10**9 * 10**(-0.4 * (m - 8.9)) * nJy

The result will be in units of nJy.

Parameters:

app_mag (float) – The apparent AB magnitude to be converted, can either be a singular value or array.

Returns:

unyt_quantity/unyt_array

The flux.

Examples using synthesizer.conversions.apparent_mag_to_fnu

An example showing how to scale a galaxy’s mass by luminosity/flux.

An example showing how to scale a galaxy's mass by luminosity/flux.

synthesizer.conversions.attenuation_to_optical_depth(attenuation)

Convert attenuation to optical depth.

Parameters:

attenuation (float) – The attenuation to convert.

Returns:

float

The converted optical depth.

synthesizer.conversions.flam_to_fnu(lam, flam)

Convert spectral flux density per wavelength to per frequency.

The conversion is done using the formula:

F_nu = F_lam * lam**2 / c

The result will be in units of nJy.

Parameters:

• lam (unyt_quantity/unyt_array) – The wavelength array the flux is defined at.

• flam (unyt_quantity/unyt_array) – The spectral flux in terms of wavelength.

Returns:

unyt_quantity/unyt_array

The spectral flux in terms of frequency, in units of nJy.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.flux_to_luminosity(flux, cosmo, redshift)

Convert flux to luminosity.

The conversion is done using the formula:

L = F * 4 * pi * D_L**2 / (1 + z)

The result will be in units of erg / s.

Parameters:

• flux (unyt_quantity/unyt_array) – The flux to be converted to luminosity, can either be a singular value or array.

• cosmo (astropy.cosmology) – The cosmology object used to calculate luminosity distance.

• redshift (float) – The redshift of the rest frame.

Returns:

unyt_quantity/unyt_array

The converted luminosity.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.fnu_to_apparent_mag(fnu)

Convert flux to apparent AB magnitude.

The conversion is done using the formula:

m = -2.5 * log10(fnu / (10**9 * nJy)) + 8.9

Parameters:

flux (unyt_quantity/unyt_array) – The flux to be converted, can either be a singular value or array.

Returns:

float

The apparent AB magnitude.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.fnu_to_flam(lam, fnu)

Convert spectral flux density per frequency to per wavelength.

The conversion is done using the formula:

F_lam = F_nu * c / lam**2

The result will be in units of erg / s / A.

Parameters:

• lam (unyt_quantity/unyt_array) – The wavelength array the flux density is defined at.

• fnu (unyt_quantity/unyt_array) – The spectral flux density in terms of frequency.

Returns:

unyt_quantity/unyt_array

The spectral flux density in terms of wavelength, in units of erg / s / Hz / cm**2.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.fnu_to_lnu(fnu, cosmo, redshift)

Convert spectral flux density to spectral luminosity density.

The conversion is done using the formula:

L_nu = F_nu * 4 * pi * D_L**2 / (1 + z)

The result will be in units of erg / s / Hz.

Parameters:

• fnu (unyt_quantity/unyt_array) – The spectral flux dnesity to be converted to luminosity, can either be a singular value or array.

• cosmo (astropy.cosmology) – The cosmology object used to calculate luminosity distance.

• redshift (float) – The redshift of the rest frame.

Returns:

unyt_quantity/unyt_array

The converted spectral luminosity density.

Raises:

IncorrectUnits – If units are missing an error is raised.

Examples using synthesizer.conversions.fnu_to_lnu

An example showing how to scale a galaxy’s mass by luminosity/flux.

An example showing how to scale a galaxy's mass by luminosity/flux.

synthesizer.conversions.llam_to_lnu(lam, llam)

Convert spectral luminosity density per wavelength to per frequency.

The conversion is done using the formula:

L_nu = L_lam * lam**2 / c

The result will be in units of erg / s / Hz.

Parameters:

• lam (unyt_quantity/unyt_array) – The wavelength array the flux is defined at.

• llam (unyt_quantity/unyt_array) – The spectral luminoisty density in terms of wavelength.

Returns:

unyt_quantity/unyt_array

The spectral luminosity in terms of frequency, in units of nJy.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.lnu_to_absolute_mag(lnu)

Convert spectral luminosity density to absolute magnitude (M).

The conversion is done using the formula:

M = -2.5 * log10(L_nu / dist_mod / (erg / s / Hz)) - 48.6

Parameters:

unyt_quantity/unyt_array – The luminosity to convert with units. Unyt

Returns:

float

The absolute magnitude.

Raises:

IncorrectUnits – If units are missing an error is raised.

Examples using synthesizer.conversions.lnu_to_absolute_mag

Camels luminosity function example

Camels luminosity function example

synthesizer.conversions.lnu_to_fnu(lnu, cosmo, redshift)

Convert spectral luminosity density to spectral flux density.

The conversion is done using the formula:

F_nu = L_nu * (1 + z) / 4 / pi / D_L**2

The result will be in units of nJy.

Parameters:

• lnu (unyt_quantity/unyt_array) – The spectral luminosity density to be converted to flux, can either be a singular value or array.

• cosmo (astropy.cosmology) – The cosmology object used to calculate luminosity distance.

• redshift (float) – The redshift of the rest frame.

Returns:

unyt_quantity/unyt_array

The converted spectral flux density.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.lnu_to_llam(lam, lnu)

Convert spectral luminoisty density per frequency to per wavelength.

The conversion is done using the formula:

L_lam = L_nu * c / lam**2

The result will be in units of erg / s / A.

Parameters:

• lam (unyt_quantity/unyt_array) – The wavelength array the luminoisty density is defined at.

• lnu (unyt_quantity/unyt_array) – The spectral luminoisty density in terms of frequency.

Returns:

unyt_quantity/unyt_array

The spectral luminoisty density in terms of wavelength, in units of erg / s / A.

Raises:

IncorrectUnits – If units are missing an error is raised.

synthesizer.conversions.optical_depth_to_attenuation(optical_depth)

Convert optical depth to attenuation.

Parameters:

depth (optical) – The optical depth to convert.

Returns:

float

The converted attenuation.

synthesizer.conversions.spatial_to_angular_at_z(spatial, cosmo, redshift)

Convert spatial distance to angular distance at a specified redshift.

Parameters:

• spatial (unyt_quantity) – The spatial distance to convert.

• cosmo (astropy.cosmology) – The cosmology object used to calculate angular diameter distance.

• redshift (float) – The redshift of the source.

Returns:

unyt_quantity

The converted angular distance in arcseconds.

synthesizer.conversions.standard_to_vacuum(wavelength)

Convert a standard wavelength into a vacuum wavelength.

Standard wavelengths are defined in vacuum at <2000A and air at >= 2000A.

Arguments

wavelength (float or unyt_array)

A standard wavelength.

Returns

wavelength (unyt_array)

A wavelength in vacuum.

synthesizer.conversions.tau_lam_to_tau_v(dust_curve, tau_lam, lam)

Convert optical depth in any given band to v-band optical depth.

Parameters:

• dust_curve (AttenuationBase) – The attenutation law to use.

• tau_lam (float) – The optical depth to convert.

• lam (unyt_quantity) – The wavelength at which tau_lam was calculated.

Returns:

float

The converted optical depth.

synthesizer.conversions.vacuum_to_air(wavelength)

Convert a vacuum wavelength into an air wavelength.

Parameters:

wavelength (float or unyt_array) – A wavelength in air.

Returns:

wavelength (unyt_array)

A wavelength in vacuum.

synthesizer.conversions.vacuum_to_standard(wavelength)

Convert a vacuum wavelength into a standard wavelength.

Standard wavelengths are defined in vacuum at <2000A and air at >= 2000A.

Arguments

wavelength (float or unyt_array)

A vacuum wavelength.

Returns

wavelength (unyt_array)

A standard wavelength.