The Extended Infrared Emission of the Southern Parts Of Orion B
A. Abergel, J. P. Bernard, F. Boulanger, M. A. Miville-Deschênes, J. L. Puget, L. Nordh, G. Olofsson, M. Huldtgren, A. A. Kaas, E. Falgarone, M. Pérault, P. André, T. Montmerle, E. Copet, P. Persi, F. Sibille;
In ISO Beyond Point Sources: Studies of Extended Infrared Emission, 2000, ISO Data Centre, Villafranca del Castillo, Madrid, Spain, R. J. Laureijs, K. Leech and M. F. Kessler, p. 119
ABSTRACT:ISOCAM observations reveal the extended emission from dense molecular clouds to low brightness diffuse regions with an unprecedented
sensitivity and angular resolution.
We present observations of the molecular
cloud L1630, located at the southern part of Orion B.
The striking
variations of the infrared color deduced from the broad-band maps of ISOCAM (from
∼5 to ∼18 microns) are combined with spectroscopic
observations.
We show that the ratio of the intensity of the aromatic features to the
continuum like emission systematically detected in interstellar spectra
around ∼15 microns strongly varies from place to place.
We suggest it is
the signature of abundance variations of two different families of
emitting particles (for instance aromatic and non aromatic particles), or of
different size distributions of one family (aromatic particles).
The
illuminated edges of dense structures have a specific infrared color due to a strong
continuum emission around 15 microns.
It may be due to a specific state of
evolution of the emitting particles, since the emission comes from a thin layer
where the emitting particles could be detached from grain mantles, and
destroyed by incident UV radiation.
The large scale emission coming from the
outer parts of dense structures presents a very different infrared color
(compatible with no continuum emission around 15 microns).
The emitting
properties of the small particles appear to evolve strongly in the interstellar
medium.
KEYWORDS: iso, infrared astronomy, molecular clouds, pahs, small particles
CODE: abergel2000