Diapositiva PPT
- Why doesn´t the spectral limitation block our calibration?
The main reason is because of all types of stars have a very similar behaviour in their Mid-IR spectra (the flux decreases with the wavelength). For instance, an AV star has a spectrum similar to an MV star, in the mid-IR.
So, if our object is a star, it does not matter if it has a different spectral type to our calibrators.
If however our object is a galaxy or a QSO we have a problem, because the spectrum of this type of object usually rises in the mid-IR. In these cases, the solution is to apply a correction factor that depends on the spectral index of the spectrum as was done for IRAS.
In the IR, a the colour term is the correction to the integrated flux that results from the convolution of the filter and the object’s spectrum, which gives us a flux in a standard band at an exactly defined wavelength.