This is my problem: I'm implementing a tool which cross-correlates a spectrum (fluxes as function of wavelength, obtained directly from an instrument) with a template (fluxes as function of wavelength, obtained by stacking observations). In order to perform such operation I have to dilate the template by multiplying the wavelength by a factor $(1+z)$ where $z$ is a floating value whose range is manually set (typically could be something like $[2.0, 2.5]$, always less than $7$). After the dilation, I have to resample this modified template so that it shares with the spectrum the same sampling (an upsampling).
This tool is actually working with $z<4$, for values of $z$ larger than this threshold I found there is a sort of aliasing effect.

Be honest, I'm not sure that it is aliasing, but looking the cross-correlation function, it shows the presence of something that looks like an aliasing effect: in the figure there are some results, in each plot, upper panel is the spectrum, bottom panel the cross-correlation function (the blue line is centered on the peak of this function, while the red line is the "true" value; but these lines are not important)

cross-correlation results

Now, these results are confusing me since I don't understand how to manage these oscillations in a spectral domain. How can I prevent this mechanism? Or how can I remove these "frequencies"?


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.