I am trying to do kinematical analysis of spectra using ppxf-algorithm from Capellari. The velocity dispersion I get seems to be to high and I am not sure what the reason could be. On the website of the ppxf algorithm ( https://pypi.org/project/ppxf/#problems-with-your-first-fit), he suggests to plot galaxy spectra and template convolved with gaussian and try to make the parameters roughly fit by eye, which I tried:
sigma = 6 # Velocity dispersion in pixels shift = 40 # Velocity shift in pixels flux_temp = np.roll(ndimage.gaussian_filter1d(flux_temp, sigma), shift) plt.plot(loglam_gal,flux_gal, 'k', label ='galaxy') plt.plot(loglam_temp, flux_temp * np.median(flux_gal) / np.median(flux_temp), 'r', label='template convolved with gaussian') plt.legend() plt.show()
Resulting in the plot:
In the middle arround the Mg-triplet this is roughly a good match I would say, on the outer parts not so much. Just looking at the plot, are there any concerns about the applicability of the ppxf-algorithm ?