NDLI: What Drives Molecular Outflows from Young Stars?

Content Provider	Springer Nature Link
Author	Ray, T.P.
Copyright Year	2000
Abstract	After briefly reviewing observations of molecular outflows from young stars, we discuss current ideas as to how they might be accelerated. Broadly speaking it is thought that such outflows represented either deflected accreted gas, or ambient material that has been pushed by a poorly collimated wind or accelerated by a highly collimated jet. Observations tend to favour the latter model, with jets being the clear favourite at least for the youngest flows. Jets from young stars may accelerate ambient gas either through the development of a boundary layer, where ambient and jet material are turbulently mixed, or at the working surface of the jet, i.e. the bow shock, via the prompt entrainment mechanism. Recently, we (Downes and Ray, 1999) have investigated, through simulations, the efficiency of prompt entrainment in jets from young stars as a means of accelerating ambient molecular gas without causing dissociation. Prompt entrainment was found to be very poor at transferring momentum from the jet to its surroundings in both the case of ``heavy'' (not surprizingly) but also ``equi-density'' (with respect to the ambient environment) jets. Moreover the transfer efficiency decreases with increasing density as the bow shock takes on a more aerodynamic shape. Models, however, in which jets are the ultimate prime movers, do have the advantage that they can reproduce several observational features of molecular outflows. In particular a power law relationship for mass versus velocity, similar to what is observed, is predicted by the simulations and the so-called ``Hubble Law'' for molecular outflows is naturally explained. Pulsing of the jet, i.e. varying its velocity, is found to have little effect on the momentum transfer efficiency at least for the dynamically young jets we have studied.
Starting Page	115
Ending Page	125
Page Count	11
File Format	PDF
ISSN	0004640X
Journal	Astrophysics and Space Science
Volume Number	272
Issue Number	1-3
e-ISSN	1572946X
Language	English
Publisher	Kluwer Academic Publishers
Publisher Date	2000-01-01
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Astronomy
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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