  To explore the high frequency radio spectra of galaxies in clusters, we used
NRAO's Very Large Array at four frequencies, 4.9-43 GHz, to observe 139
galaxies in low redshift (z<0.25), X-ray detected, clusters. The clusters were
selected from the survey conducted by Ledlow & Owen, who provided redshifts and
1.4 GHz flux densities for all the radio sources. We find that more than half
of the observed sources have steep microwave spectra as generally expected
(alpha<-0.5, in the convention S \propto nu^alpha). However, 60-70% of the
unresolved or barely resolved sources have flat or inverted spectra. Most of
these show an upward turn in flux at nu>22 GHz, implying a higher flux than
would be expected from an extrapolation of the lower frequency flux
measurements. Our results quantify the need for careful source subtraction in
increasingly sensitive measurements of the Sunyaev-Zel'dovich effect in
clusters of galaxies (as currently being conducted by, for instance, the
Atacama Cosmology Telescope and South Pole Telescope groups).
