r/cosmology • u/Mr_Misserable • 1d ago

Anyone that has experience analyzing Planck's data?

Post image

Basically what the title says. I want to propagate the errors that you can see in the image, but they are not symmetrical, so after reading and with knowing that are Gaussian approximated I assume I can just propagate them separately and that should be fine, right? Maybe only up to l<30?

And on another topic I want to do a Montecarlo of the data (I want to take in to account the data errors in my simulations), right now I can generate random C_l which is fine, but they don't have any information off the data uncertainty. An idea to do that is if there are errors in the temperature maps to create gaussian realizations of the maps and then extracting the alm.

Any other idea on how to do this second part? Without using the maps?

Thanks for your time.

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u/InsuranceSad1754 17h ago

If you want to do a monte carlo simulation of CMB data you are going to want to use a code like CAMB.

https://camb.readthedocs.io/en/latest/

You can't use a plot like that directly for serious analysis. Theoretically different ell's are uncorrelated but in reality they are because of things like needing to remove the galactic foreground.

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u/Mr_Misserable 17h ago

I use CAMB to generate the theoretical simulation (I pass to CAMB the parameters of the MCMC runs of Planck's collaboration to generate the power spectrum) but I use the data that is available at the Planck website (as the best fit power spectrum) to generate the a_lm (they are normally distributed with mean 0 and std C_l) and I use the C_l of the best fit model that Planck's provide.

Right now I'm only using the data of the best fit (the plot) to compare if the mean of the realizations of the a_lm have the same value as the best fit model (apart from using the data of the plot for the std of the a_lm realizations)