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domeckert / pyproffit

Pyproffit is a Python code for the analysis of X-ray brightness profiles from clusters of galaxies
GNU General Public License v3.0
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Different power spectrum results given same sb model #23

Closed ktrehaeven closed 10 months ago

ktrehaeven commented 1 year ago

Hi

I'm trying to get the power spectrum (ps) of surface brightness (sb) residuals for a cool-core galaxy cluster. However, identical runs of the ps analysis gives different results. I've been using a double beta model. I've attached a screenshot of the parameters that the sb fitting converges to, as well as the ps and amplitude plots from identical runs using these same model parameters. Sometimes the variation is within the calculated uncertainties, sometimes not. I'm not sure if this is a matter of SNR or if something deeper is responsible. The obs is > 100 ks but I'm using a binsize of 1.476 arcsec (3 chandra pixels) to determine the profile. sb_model_parameters sb_model_profile power_spectrum.inner_200kpc_radius1.pdf power_spectrum.inner_200kpc_radius2.pdf

a2d.inner_200kpc_radius1.pdf a2d.inner_200kpc_radius2.pdf

domeckert commented 1 year ago

Hi @ktrehaeven . I need to look into the power spectrum part but in any case it seems obvious from your plots that you have an issue with the background subtraction, which may be responsible for the differences that you find. I suspect that you may have subtracted the sky backkground multiple times from the same surface brightness profile, which resulted in over-subtraction.

The point is, please check your background subtraction first and find an appropriate fit to the surface brightness, otherwise the 2D model will be wrong and you will end up with different power spectra.

ktrehaeven commented 1 year ago

Thank you very much for the guidance. I re-fitted after the subtraction and much of the variation has disappeared and the amplitude and power spectrum plots more or less seem to be consistent. Thanks! Kind regards Keegan Trehaeven

On Fri, Jul 21, 2023 at 8:22 AM Dominique Eckert @.***> wrote:

Hi @ktrehaeven https://github.com/ktrehaeven . I need to look into the power spectrum part but in any case it seems obvious from your plots that you have an issue with the background subtraction, which may be responsible for the differences that you find. I suspect that you may have subtracted the sky backkground multiple times from the same surface brightness profile, which resulted in over-subtraction.

The point is, please check your background subtraction first and find an appropriate fit to the surface brightness, otherwise the 2D model will be wrong and you will end up with different power spectra.

— Reply to this email directly, view it on GitHub https://github.com/domeckert/pyproffit/issues/23#issuecomment-1645043651, or unsubscribe https://github.com/notifications/unsubscribe-auth/ASRMRFA53IYAZ5343UFJKJLXRIN2FANCNFSM6AAAAAA2OSWGYI . You are receiving this because you were mentioned.Message ID: @.***>