Spitzer Space Telescope observations of the Carina Nebula: The steady
  march of feedback-driven star formation
  We report the first results of imaging the Carina Nebula with Spitzer/IRAC,
providing a catalog of point sources and YSOs based on SED fits. We discuss
several aspects of the extended emission, including dust pillars that result
when a clumpy molecular cloud is shredded by massive star feedback. There are
few "extended green objects" (EGOs) normally taken as signposts of outflow
activity, and none of the HH jets detected optically are seen as EGOs. A
population of "extended red objects" tends to be found around OB stars, some
with clear bow-shocks. These are dusty shocks where stellar winds collide with
flows off nearby clouds. Finally, the relative distributions of O stars and
subclusters of YSOs as compared to dust pillars shows that while some YSOs are
located within pillars, many more stars and YSOs reside just outside pillar
heads. We suggest that pillars are transient phenomena, part of a continuous
outwardly propagating wave of star formation driven by massive star feedback.
As pillars are destroyed, they leave newly formed stars in their wake, which
are then subsumed into the young OB association. Altogether, the current
generation of YSOs shows no strong deviation from a normal IMF. The number of
YSOs suggests a roughly constant star-formation rate over the past 3Myr,
implying that star formation in pillars constitutes an important mechanism to
construct unbound OB associations. Accelerated pillars may give birth to O-type
stars that, after several Myr, could appear to have formed in isolation.
