Next: C.2 Computation of Colour Up: C. Colour Corrections Previous: C. Colour Corrections

C.1 Application of Tabulated Colour Correction Factors

The flux densities quoted in the ISOPHOT AAR results have been derived from the detector in-band powers assuming an energy distribution of the source which is constant in the flux per logarithmic frequency interval; i.e., the flux density with frequency $\nu$ goes as $f_{\rm\nu} \propto \nu^{-1}$ . This is the same convention as used for IRAS data.

In order to derive the flux density for any other spectral energy distribution (SED) a `colour correction' must be applied to the background subtracted source flux density in the following way:

$\begin{displaymath} F_{\rm\nu_{\rm ref}}(SED) = F_{\rm\nu_{\rm ref}}(\nu^{-1})~/~K_{\rm cc}(SED) \end{displaymath}$

(C.1)

where:


   = flux density for applied SED

   = quoted flux density in AAR

   = tabulated colour correction factor for applied SED

Tabulated colour correction factors are available for

1): power-laws $F(\nu^{\alpha}), -3~\le~\alpha~\le~+3$
$\rightarrow$ Cal-G file PCCPOWER
2): black bodies $F(B(\nu,T))$
$\rightarrow$ Cal-G file PCCBB
3): modified black bodies $F(\nu^{+1} \cdot B(\nu,T))$ and $F(\nu^{+2} \cdot B(\nu,T))$
$\rightarrow$ Cal-G files PCCMBBONE and PCCMBBTWO

Next: C.2 Computation of Colour Up: C. Colour Corrections Previous: C. Colour Corrections

ISO Handbook Volume IV (PHT), Version 2.0.1, SAI/1999-069/Dc