  We report the first detection of gas-phase CO2 emission in the star-forming
region Cepheus A East, obtained by spectral line mapping of the v2 bending mode
at 14.98 micron with the Infrared Spectrograph (IRS) instrument onboard the
Spitzer Space Telescope. The gaseous CO2 emission covers a region about 35'' x
25'' in extent, and results from radiative pumping by 15 micron continuum
photons emanating predominantly from the HW2 protostellar region. The gaseous
CO2 exhibits a temperature distribution ranging from 50 K to 200 K. A
correlation between the gas-phase CO2 distribution and that of H2 S(2), a
tracer of shock activity, indicates that the CO2 molecules originate in a cool
post-shock gas component associated with the outflow powered by HW2. The
presence of CO2 ice absorption features at 15.20 micron toward this region and
the lack of correlation between the IR continuum emission and the CO2 gas
emission distribution further suggest that the gaseous CO2 molecules are mainly
sputtered off grain mantles -- by the passage of slow non-dissociative shocks
with velocities of 15-30 km/s -- rather than sublimated through grain heating.
