Silicon is overabundant in the center of the Perseus Cluster
Silicon is overabundant in the center of the Perseus Cluster
We have fitted the spectra of the inner 4 arcmin region of the Perseus
cluster with a two temperature plasma emission model with the low temperature
component having additional absorption. We have allowed the silicon
and sulfur abundances to be a free parameter, independent of the other
elemental abundances, which were tied together. The contour plot
below shows the one, two, and three sigma confidence regions. We can conclude
that silicon is 1.5 - 2 times as abundant as sulfur (which has
an abundance consistent with the other elements). The lines determining the
silicon and sulfur abundances are K shell transitions with similar temperature
dependencies so this result is based on well known atomic physics and should
be relatively insensitive to the precise continuum model fitted to the spectra.
This result is consistent with the result from the Einstein FPCS
spectroscopy that oxygen is several times as abundant as iron in the core
of the Perseus Cluster and is expected if ejecta from massive stars are
the source of the heavy metals in the intracluster gas.