Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.281p&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Astronomy and Astrophysics
Astronomy
Scientific paper
Protostellar outflows play a crucial role in molecular cloud evolution and star formation, by transferring momentum and energy back to the ambient medium, thereby, allowing new chemical processes to occur. The chemical manifestations depend on the nature of the shocks, if they are J or C type (Hollenbach 1997). In turn, it depends on the shock velocity, magnetic field strength and fractional ionization in the preshock gas. These processes lead to species abundance enhancements up to several orders of magnitude, as reported in "chemically active" outflows (Bachiller 2001) with differences not only between sources but also between regions of the same flow. There is now direct evidence that outflows contribute to the chemical enrichment of the interstellar gas (Arce et al. 2008; Codella et al. 2009). However, the actual degree of chemical complexity achieved in protostellar shocks is poorly contrained. To address this issue, we have started an unbiased survey of the millimeter line emission of the Cep E outflow. Cep E is an intermediate-mass class 0 protostar candidate (Lefloch 1996), situated in the Cep OB3 association at 725 pc (Johnson 1959) with a Lbol of ~100 Lsun. We observed the central protostellar source and the apex of the terminal Southern bowshock in order to quantify the chemistry induced by the shock. The observations were carried out in winter 2009-2010 and 2010-11 at the IRAM 30m telescope in the bands at 3mm (80-115GHz), 1.3mm (208-282GHz) and 0.8mm (329-350 GHz), reaching a rms of about 5mK per interval of 2MHz. These observations provide us with one of the most comprehensive census of the chemical composition of a protostellar outflow, and allow us to establish that the outflow associated with Cep E is probably at least as rich as L1157's one. In this work, we discuss and analyse the differences of the chemical composition and the properties of the molecular gas, associated with the protostellar envelope, the entrained (low-velocity), outflowing gas, and the driving jet. We have identified about 30 different species. In general, simple O-bearing species are detected in the jet while typical hot core species and cold gas tracers (e.g. deuterated species) are detected towards the protostellar source. Also, we have detected a narrow line component associated with CH3OH, in addition on the broad lines profiles coming from the shock.
Ceccarelli Cecilia
Lefloch Bertrand
Pacheco Vazquez S.
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