  We present ISOPHOT P32 oversampled maps and P37/39 sparse maps, of three
bright elliptical galaxies in the Virgo Cluster. The maps reach the limiting
sensitivity of the ISOPHOT instrument at 60, 100, 170 and 200 microns. Two
elliptical galaxies show no emission at all far-IR ISOPHOT wavelengths at a
level of few tens of mJy. The null detection provides a test of the evolution
of dust in elliptical galaxies and its size distribution and composition. As
previous studies have shown, in many elliptical galaxies both IRAS and ISO have
detected mid-IR excess 6-15 micron emission relative to the stellar continuum
indicating emission from circumstellar dust. Under the assumption that these
dusty outflows from evolving red giant stars and planetary nebulae are
continuously supplying dust to the interstellar medium, we have computed the
infrared luminosity at the ISOPHOT bands appropriate for NGC4472. The null
far-IR ISOPHOT observations exceed the far-IR flux expected from dust expelled
from a normal old stellar population.
