P. André 1, S. Cabrit 2, S. Bontemps 3, G. Olofsson 3, M. Wolfire 4, M. Corcoran 1, F. Boulanger 5, & M. Casali 6 et al.
1 CEA Saclay
2 DEMIRM, Obs. Paris
3 Stockholm Obs.
4 Univ. of Maryland
5 IAS Orsay
6 ROE Edinburgh
We present and discuss the results of full CVF spectra taken with ISOCAM
between 5 and 17 
towards a sample of 20 low-luminosity, deeply
embedded
young stellar objects (YSOs). Our sample mostly comprises Class 0 protostars
undetected by IRAS at 12
but characterized by strong emission in the
submillimeter continuum and powerful jet-like outflows. These Class 0
objects have measured envelope masses larger than their estimated
central stellar masses, and are thus likely at the beginning of the main
protostellar accretion phase (typical age
). They often
exhibit
spectroscopic signatures of gravitational collapse.
Detailed studies of such young protostars are of prime interest to shed light
on the physics of the earliest stages of star formation.
The CVF spectra we obtained generally exhibit prominent solid-state absorption
features due to various ices of e.g. H2O, CH4, CO2.
The 13
libration mode
of water ice is clearly seen in several objects.
By comparing the depths and shapes observed for the 9.7 mu Silicate absorption
feature with the results of dust radiative transfer calculations, we derive
strong constraints on the inner structure (e.g. column density and inner
radius) of young protostellar envelopes. Our sources typically have Av > 100
and
.
We also discuss the abundances of CO2 and H2O ices in these protostellar
envelopes. Finally, the meaning of the (5 - 8 )/(12 - 17 )
(i.e. LW2/LW3) color ratio for deeply embedded YSOs is assessed.