bandpass: Filter Band Pass

In asgr/ProSpect: Professional Spectral Analysis Package

Filter Band Pass

Description

Put a spectrum through a filter response, returning either the modified spectrum or the integrated flux.

Usage

bandpass(wave, flux, filter, flux_in = 'freq', flux_out = 'freq',
detect_type = 'photon')

Arguments

wave	Observed wavelength in Angstroms by default (see wavefac). 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 flux.
flux	Numeric vector; flux spectral density in erg/s / cm^2 / Hz or erg/s / cm^2 / Ang units (see flux_in and flux_out and conversion in the Example).
filter	Two column matrix; column one must be flux in Angstroms, column two must be a filter response. These are the type returned by getfilt (see Examples). You can also pass in a function (e.g. the output of approxfun run on the filters), which will result in faster processing.
flux_in	Character scalar; the input type of flux spectral density used. Should be either 'freq' (default, power per Hz) or 'wave' (power per Ang)
flux_out	Character scalar; the output type of flux spectral density desired. Should be either 'freq' (default, power per Hz) or 'wave' (power per Ang)
detect_type	Character scalar; the type of detector used for the photometric system. Should be either 'photon' (default) or 'energy'. See Details.

Details

This is a lower level function that might be useful to use directly. For most use cases a direct conversion using e.g. magABcalc is probably more useful.

The type of detector is important to ensure the correct sort of filter operation is made to calculate the average flux at the effective wavelength.

For photon counters we must use (where R is the filter response/transmission):

F(\lambda_{eff}) = \frac{\int R(\lambda) F(\lambda) \lambda d\lambda}{\int R(\lambda) \lambda d\lambda}

For energy counters we must use:

F(\lambda_{eff}) = \frac{\int R(\lambda) F(\lambda) d\lambda}{\int R(\lambda) d\lambda}

Note the F(\lambda) \lambda d\lambda parts can be directly replaced by F(\nu) \lambda d\nu.

Value

Returns the mean weighted flux across the filter.

Author(s)

Aaron Robotham

See Also

photom, magABcalc, getfilt, SFHfunc

Examples

fluxBC03=Lum2Flux(BC03lr$Wave, BC03lr$Zspec[[5]][161,]*1e10)

#The below should give the same answers (6.515128e-28):

CGScalc(fluxBC03)
bandpass(fluxBC03[,1], (1e-10*fluxBC03[,2]*fluxBC03[,1]^2)/299792458,
filter=getfilt('r_VST'))
bandpass(fluxBC03[,1], convert_wave2freq(fluxBC03[,2], fluxBC03[,1]),
filter=getfilt('r_VST'))
bandpass(fluxBC03[,1], fluxBC03[,2], flux_in='wave', filter=getfilt('r_VST'))

#Alternatively we can output in <F_lambda> and use the pivot wavelength of r_VST
#(6312.451 Ang) to convert to <F_freq>:

bandpass(fluxBC03[,1], fluxBC03[,2], flux_in='wave', flux_out='wave',
filter=getfilt('r_VST')) * (6312.451^2)*1e-10/299792458

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