Spitzer Mid-Infrared Spectra of Cool-Core Galaxy Clusters
  We have obtained mid-infrared spectra of nine cool-core galaxy clusters with
the Infrared Spectrograph aboard the Spitzer Space Telescope. X-ray,
ultraviolet and optical observations have demonstrated that each of these
clusters hosts a cooling flow which seems to be fueling vigorous star formation
in the brightest cluster galaxy. Our goal is to use the advantages of the
mid-infrared band to improve estimates of star formation. Our spectra are
characterized by diverse morphologies ranging from classic starbursts to flat
spectra with surprisingly weak dust features. Although most of our sample are
known from optical/UV data to be active star-formers, they lack the expected
strong mid-infrared continuum. Star formation may be proceeding in unusually
dust-deficient circumgalactic environments such as the interface between the
cooling flow and the relativistic jets from the active galactic nucleus.
