photom: Spectral Processing for Photometry

In asgr/ProSpect: Professional Spectral Analysis Package

Spectral Processing for Photometry

Description

These functions can manipulate restframe spectra in useful ways, e.g. placing it at a target redshift with the correct observed luminosity and band stretching.

Usage

photom_flux(wave, flux, outtype = 'mag', filters = "all")
photom_lum(wave, lum, outtype = 'mag', filters = "all", z = 0.1, H0 = 67.8,
OmegaM = 0.308, OmegaL = 1 - OmegaM, ref, LumDist_Mpc = NULL)
Lum2Flux(wave, lum, z = 0.1, H0 = 67.8, OmegaM = 0.308, OmegaL = 1 - OmegaM,
  ref, LumDist_Mpc = NULL)
Flux2Lum(wave, flux, z = 0.1, H0 = 67.8, OmegaM = 0.308, OmegaL = 1 - OmegaM,
  ref, LumDist_Mpc = NULL)
Lum2FluxFactor(z = 0.1, H0 = 67.8, OmegaM = 0.308, OmegaL = 1 - OmegaM, ref, 
  LumDist_Mpc = NULL)

Arguments

wave	Numeric vector; the spectral wavelength in Angstroms. For convenience, if a two column matrix or data frame is supplied then the first column is taken to be wave and the second is taken to be lum.
flux	Numeric vector; flux density in erg/s / cm^2 / Angstrom spectral units.
lum	Numeric vector; the spectral luminosity in Lsol / Angstrom (BC03lr / BC03hr and EMILES format).
outtype	Character scalar; specifies the type of photometry computed, must be one of 'mag' / 'magAB' (for AB magnitudes, the default), 'Jansky' / 'Jy' (for Jansky fluxes) or 'CGS' (for CGS fluxes). See magABcalc for details.
filters	Character vector; names of filters to use. See filters for options. Default 'all' selects all filters, 'GAMA' returns just the classic GAMA survey filters.. If not a character then this will be passed onto bandpass, and may therefore be a list of filter responses, or even better (faster) a list of filter functions.
z	Numeric scalar; cosmological redshift. If z <= 0 then the source will be placed at 10 Parsecs, i.e. this is what you want if you are aiming to compute Absolute Magnitudes.
H0	Numeric scalar; Hubble constant as defined at z=0 (default is H0=100 (km/s)/Mpc).
OmegaM	Numeric scalar; Omega Matter today (default is 0.3).
OmegaL	Numeric scalar; Omega Lambda today (default is for a flat Universe with OmegaL = 1-OmegaM-OmegaR = 0.7).
ref	The name of a reference cosmology to use, one of 137 / 737 / Planck / Planck13 / Planck15 / Planck18 / WMAP / WMAP9 / WMAP7 / WMAP5 / WMAP3 / WMAP1 / Millennium / GiggleZ. Planck = Planck18 and WMAP = WMAP9. The usage is case insensitive, so wmap9 is an allowed input. This overrides any other settings for H0, OmegaM and OmegaL. If OmegaR is missing from the reference set then it is inherited from the function input (0 by default). See cosref for details.
LumDist_Mpc	Numeric scalar; Luminosity distance computed in units of cm. Default is NULL. The luminosity distance can be supplied for repeated computations when the redshift of the object is constant. This should be supplied using the "correct" cosmology (as near as possible), i.e. using H0 ~ 70 km/s/Mpc (not 100).

Details

photom_lum is a useful utility function since it fully converts between an intrinsic spectrum (e.g. of the type created when integrating a star formation history over differ stellar population models) all the way to a band-pass magnitude in AB mags (or Jy or CGS). The latter is how many surveys represent their photometry, so this is usually a sensible unit space to use for feature fitting etc. In some circumstances fluxes (CGS or Jansky type) might be more appropriate, espeically when signal to noise is low a meaurements might be negative.

Value

photom_flux	Numeric vector; output flux (AB mag by default).
photom_lum	Numeric vector; output flux (AB mag by default).
Lum2Flux	Numeric Matrix; first column is observed wavelength (Angstroms) and second column is observed flux (erg/s/cm^2/Angstrom).
Flux2Lum	Numeric Matrix; first column is observed wavelength (Angstroms) and second column is observed luminosity (Lsol / Ang).
Lum2FluxFactor	Numeric scalar; the scaling factor to convert between intrinsic Lsol/Angstrom and erg/s/cm^2/Angstrom.

Author(s)

Aaron Robotham

References

Bruzual and Charlot, 2003, MNRAS, 344, 1000

See Also

SFHfunc

Examples

data('cenwave')

#Make a 10^10 solar mass SSP that is 5 Grys old and solar metallicity:

#First with BC03lr:
BC03lr$Age[161]

photoBC03=photom_lum(BC03lr$Wave, BC03lr$Zspec[[5]][161,]*1e10)
plot(cenwave[,2], photoBC03, log='x', ylim=c(26,17), xlab=BC03lr$Labels$Wavelab,
ylab='Mag', col=rev(rainbow(34, end=2/3)), pch=16)

#Next with EMILES
EMILES$Age[35]

photoEMILES=photom_lum(EMILES$Wave, EMILES$Zspec[[9]][35,]*1e10)
plot(cenwave[,2], photoEMILES, log='x', ylim=c(26,17), xlab=BC03lr$Labels$Wavelab,
ylab='Mag', col=rev(rainbow(34, end=2/3)), pch=16)

#We can show the flux directly too:

fluxBC03=Lum2Flux(BC03lr$Wave, BC03lr$Zspec[[5]][161,]*1e10)
plot(fluxBC03, log='xy', xlab=BC03lr$Labels$Wavelab, ylab='Flux / erg/s/cm^2/Angstrom',
type='l')

asgr/ProSpect documentation built on Feb. 21, 2025, 1:43 a.m.