Stars in their young age are pretty messy. They spend the beginning
of their lives enshrouded in thick clouds of dust, rendering them
invisible to the naked eye. Young massive stars in particular
sometimes emit large amount of radiation at infrared wavelengths,
believed to arise from hot dust grains in their immediate
vicinity. However, the exact origin of this emission is still unknown.
Infrared cameras allow to peer at their dusty environment, which
may constitute the building blocks from which future planetesimals
will form.
AFGL 4029 is a luminous bipolar outflow source associated with a
young embedded cluster of massive stars, located 2.2 kpc from the
sun. We show the image obtained at CFHT with the mid-infrared camera
CAMIRAS (Right) compared with the one from the infrared camera on
board of ISO, the european infrared satellite (Left). The
unprecedented high spatial resolution provided by the CFHT image
allows to study in details the morphology of the emission, thus
providing information on the nature of the dust as well as the process
by which it is heated.
Mid-infrared emission arises from hot dust grains primarily heated
by the strong UV field of the close young massive stars. The
mid-infrared emission in AFGL 4029 is clearly dominated by two strong
sources: IRS 1 (on the right of the image) is a young star still deeply
enshrouded in dust (more than 30 magnitudes of extinction in the
visible!) and the likely source of the outflow, IRS 2 (to the left) is
a B1 star which ionizes its surrounding, creating around it a bubble
of hot matter. The mid-infrared emission is clearly resolved spatially
in both sources. The extended circular emission observed around IRS 2
coincides remarkably with the known extent of the ionized bubble
around the central exciting star. These observations also indicate
the presence of a large tenuous enveloppe of small dust particles
surrounding IRS 1, most likely a cavity evacuated by the outflow. The
arc-shaped nebula to the right of IRS 1 is a reflection
nebula. Its strong brightness suggests that it is enriched in small
particles, maybe originating in shocks along the outflow.
This image was obtained with the CAMIRAS instrument, a camera working
in the mid-infrared (10 to 20 microns). CAMIRAS is a visitor
instrument built by the CEA -Saclay (FRANCE) and operated at the
CFHT. The pixel size is 0.3" and field of view 57"x38". The image
presented here was taken on July 1996 through narrow-band filters
ranging from 8 to 12 microns, sensitive both to the continuum emission
from the dust and to the infrared emission bands characteristic of
small carboneous dust grains.
Technical description: