A two-temperature model is the best fit
A two-temperature model is the best fit
The best model that we have been able to find for the cores of
cooling flow clusters is a simple two-temperature plasma with
the lower temperature component having an additional amount of
absorption above that from the Galaxy. This model provides a
better fit to the data than a model with a hot component and
an absorbed cooling flow component. The cooling flow model provides
as good a fit as the two-temperature model if the low temperature
cut-off of the cooling flow is allowed to increase to above 1 keV.
The figure below shows the residual and ratio plots between the data
and the two-temperature model for the spectra from the inner 2 arcmin
region of the Perseus cluster.
The residuals just below 2 keV are the silicon lines and appear because
we have held all the metals to the Solar photospheric relative abundances.
The feature at ~2.3 keV is instrumental. There is structure in the low energy
residuals that we cannot fit with this model. This structure buttresses our
contention that the actual spectrum in this energy range is more complicated
than the simple approximations we have tried up to now.