Skip to main content
next up previous contents
Next: vgauss, zvgauss: gaussian line Up: Additive Model Components Previous: wdem, vwdem, vvwdem, bwdem,   Contents


vagauss, zvagauss: gaussian line profile in wavelength space with sigma in velocity

A simple gaussian line profile in wavelength. If the width is $\leq 0$ then it is treated as a delta function. The zagauss variant computes a redshifted gaussian.

$\displaystyle A(\lambda) = K {1\over{(\sigma/c)\sqrt{2\pi}}} \exp(-(\lambda-\lambda_l)^2/2(\sigma/c)^2) $

where:

par1 = $\lambda_l$ line wavelength in Angstrom
par2 = $\sigma$ line width in km/s
Norm = K total photons/cm$^2$/s in the line

For zvagauss the corresponding formula is:

$\displaystyle A(\lambda) = K {(1+z)\over{(\sigma/c)\sqrt{2\pi}}} \exp(-(\lambda/(1+z)-\lambda_l)^2/2(\sigma/c)^2) $

and the parameters are:

par1 = $\lambda_l$ line wavelength in Angstrom
par2 = $\sigma$ line width in km/s
par3 = z redshift
Norm = K total photons/cm$^2$/s in the line

The line is truncated at the point that the integrated flux under the line is within a critical value of the total flux. This critical value can be changed using xset LINECRITLEVEL. The default critical value is $1.0\times10^{-6}$.

next up previous contents
Next: vgauss, zvgauss: gaussian line Up: Additive Model Components Previous: wdem, vwdem, vvwdem, bwdem,   Contents