Fluxes, colour excess and attenuation

galaxy.photometry.calzetti_law(lbda: Union[float, numpy.ndarray], rv: float = 4.05, a: float = 2.659, b1: float = - 1.857, c1: float = 1.04, d1: float = 0, e1: float = 0, b2: float = - 2.156, c2: float = 1.509, d2: float = - 0.198, e2: float = 0.011) → Union[float, numpy.ndarray][source]

Code author: Epinat Benoit - LAM <benoit.epinat@lam.fr>

Attenuation curve from Calzetti et al. (2000). The coefficients can be modified in input.

Note

In principle, this law is valid from 0.12 to 2.2 microns.

The relation is

\[k = a \times (b + c/\lambda + d/\lambda^2 + e/\lambda^3),\]

with \(\lambda\) the wavelength.

Parameters

  • lbda (float or ndarray[float]) – wavelength in microns

  • rv (float) – (Optional) ratio of the total to selective attenuation

  • a (float) – (Optional) multiplicative coefficient

  • bi (float) – (Optional) coefficients for the relation above 0.63 microns

  • bi – (Optional) coefficients for the relation below 0.63 microns

Returns

Calzetti attenuation

Return type

float or ndarray[float]

galaxy.photometry.dust_attenuation_calzetti(lbda: Union[float, numpy.ndarray], ebv: float, rv: float = 4.05) → Union[float, numpy.ndarray][source]

Code author: Epinat Benoit - LAM <benoit.epinat@lam.fr>

Compute the dust attenuation using the Calzetti attenuation curve (could be more general adding a function name) from the colour excess.

Parameters

  • lbda (float or ndarray[float]) – wavelength in microns

  • ebv (float) – colour excess

  • rv (float) – (Optional) ratio of the total to selective attenuation

Returns

dust attenuation in mag

Return type

float or ndarray[float]

galaxy.photometry.cardelli_law(lbda: Union[float, numpy.ndarray], rv: float = 3.1) → Union[float, numpy.ndarray][source]

Code author: Epinat Benoit - LAM <benoit.epinat@lam.fr>

Attenuation curve from Cardelli et al. (1989). The coefficients can be modified in input.

Note

In principle, this law is valid from 0.1 to 3.3 microns. For MW, Rv~3.1.

Parameters

  • lbda (float or ndarray[float]) – wavelength in microns

  • rv (float) – (Optional) ratio of the total to selective attenuation

Returns

cardelli attenuation

Return type

float or ndarray[float]

galaxy.photometry.dust_attenuation_cardelli(lbda: Union[float, numpy.ndarray], ebv: float, rv: float = 3.1) → Union[float, numpy.ndarray][source]

Code author: Epinat Benoit - LAM <benoit.epinat@lam.fr>

Compute the dust attenuation using the Cardelli attenuation curve from the colour excess.

Parameters

  • lbda (float or ndarray[float]) – wavelength in microns

  • ebv (float) – colour excess

  • rv (float) – (Optional) ratio of the total to selective attenuation

Returns

dust attenuation in mag

Return type

float or ndarray[float]

galaxy.photometry.flux_to_lum(floii: Union[float, numpy.ndarray], z: Union[float, numpy.ndarray], av: Optional[Union[float, numpy.ndarray]] = None, ebv: Optional[Union[float, numpy.ndarray]] = None, lbda: Union[float, numpy.ndarray] = 0.3728) → Union[float, numpy.ndarray][source]

Code author: Epinat Benoit - LAM <benoit.epinat@lam.fr>

Convert a flux into a luminosity. If an attenuation and a colour excess are given, the flux is corrected beforehand.

Parameters

  • floii (float or ndarray[float]) – flux in \(\rm{erg/s/cm^2}\). Optionally, can directly be given as an Astropy Quantity with a unit of the kind \(\rm{erg/s/cm^2}\).

  • z (float or ndarray[float]) – redshift

  • av (float or ndarray[float]) – (Optional) attenuation in V band

  • ebv (float or ndarray[float]) – (Optional) colour excess

  • lbda (float or ndarray[float]) – (Optional) rest-frame wavelength in microns

Returns

luminosity in \(\rm{erg/s}\)

Return type

float or ndarray[float]

galaxy.photometry.correct_extinction(floii: Union[float, numpy.ndarray], z: Union[float, numpy.ndarray], av: Union[float, numpy.ndarray], ebv: Union[float, numpy.ndarray], lbda: Union[float, numpy.ndarray] = 0.3728) → Union[float, numpy.ndarray][source]

Code author: Epinat Benoit - LAM <benoit.epinat@lam.fr>

Correct for both galactic extinction and internal extinction. We use the following attenuation curves:

  • Cardelli for the Galactic extinction

  • Calzetti for the intrinsic extinction

Parameters

  • av (float or ndarray[float]) – attenuation in V band

  • ebv (float or ndarray[float]) – colour excess

  • floii (float or ndarray[float]) – ionised gas flux

  • z (float or ndarray[float]) – redshift

  • lbda (float or ndarray[float]) – (Optional) rest-frame wavelength in microns

Returns

flux corrected of extinction

Return type

float or ndarray[float]