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Next: Density structure of prestellar Up: Poster session C Interstellar Previous: Search for cool circumstellar

Mid-infrared spectral energy distributions of deeply embedded protostars

P. AndrĂ© 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 $\rm\mu m$ 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 $\rm\mu m$ 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 $\rm < 10^4-10^5 yr$). 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 $\rm\mu m$ 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 $\rm R_{in} \sim 100\, AU$. We also discuss the abundances of CO2 and H2O ices in these protostellar envelopes. Finally, the meaning of the (5 - 8 $\rm\mu m$)/(12 - 17 $\rm\mu m$) (i.e. LW2/LW3) color ratio for deeply embedded YSOs is assessed.


next up previous contents index
Next: Density structure of prestellar Up: Poster session C Interstellar Previous: Search for cool circumstellar
"The Universe as seen by ISO", 20 - 23 October 1998, Paris: Abstract Book