Astronomy and Astrophysics, volume 311, 858-872 (1996/7-3)
Evolution of outflow activity around low-mass embedded young stellar objects.
BONTEMPS S., ANDRE P., TEREBEY S. and CABRIT S.
Abstract (from CDS):
We present a detailed study of outflow activity in a sample of 45 low-luminosity embedded young stellar objects (YSOs). We use maps in the J=2-1 line of 12CO to characterize this activity for YSOs that are still sufficiently embedded to show molecular outflows. Our CO outflow survey benefits from coordinated millimeter continuum measurements of circumstellar masses which allow us to estimate the evolutionary states of the central driving sources. Our sample comprises 36 near-IR (Class I) protostars and 9 far-IR/submm (Class 0) protostars, and should be representative of the ``self-embedded'' phase of (low-mass) protostellar evolution characterizing young stars still surrounded by significant circumstellar envelopes. We find that virtually all the objects in our sample have detectable CO outflow activity. We make homogeneous estimates of the outflow momentum flux deposited in the close environment of the driving sources in order to assess the dynamical properties of the underlying driving winds/jets. As is well-known, a tight correlation between outflow energetics and driving source luminosity is found for Class I sources. However, Class 0 sources lie a factor of ∼10 above this correlation, suggesting they have qualitatively different (e.g., more powerful) CO outflows. In addition, we find that the outflow momentum flux correlates well with the circumstellar envelope mass of the exciting source for both Class I and Class 0 sources. We show that this new correlation is independent of the FCO-Lbol correlation and most likely results from a more or less continuous decrease of outflow power with time during the accretion phase. For a young star of final mass ∼0.6M☉, the outflow momentum flux is typically FCO∼10–4M☉.km/s/yr at the early Class 0 stage and FCO∼2x10–6M☉.km/s/yr at the late Class I stage. We suggest that this decrease of outflow energetics reflects a corresponding decay in the mass accretion/infall rate.
stars: formation - ISM: jets and outflows - radio lines: ISM - stars: pre-main sequence - radio lines: stars
Table 1 : IRS 67 = [GWA94] 6, IRAS 04489+3032 misprint for 3042, IRAS 16445-1405 misprint for 16455, IRAS 16442-0929 = 16442-0930
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