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Evolution of Hubble wedges in episodic protostellar outflows

Rohde, P F, Walch, S, Seifried, D, Whitworth, A P, Clarke, S D and Hubber, D A 2018. Evolution of Hubble wedges in episodic protostellar outflows. Monthly Notices of the Royal Astronomical Society 483 (2) , pp. 2563-2580. 10.1093/mnras/sty3302

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Young low-mass protostars undergo short phases of high accretion and outburst activity leading to lumpy outflows. Recent observations have shown that the position–velocity and mass–velocity diagrams of such outflows exhibit individual bullet-like features; some of these bullets subscribe to a ‘Hubble Law’ velocity relation, and others are manifest as ‘Hubble wedges’. In order to explore the origin of these features, we have developed a new episodic outflow model for the SPH code gandalf, which mimics the accretion and ejection behaviour of FU-Ori-type stars. We apply this model to simulations of star formation, invoking two types of initial conditions: spherically symmetric cores in solid-body rotation with ρ ∝ r−2, and spherically symmetric turbulent cores with density proportional to the density of an Bonnor–Ebert sphere. For a wide range of model parameters, we find that episodic outflows lead to self-regulation of the ejected mass and momentum, and we achieve acceptable results, even with relatively low resolution. Using this model, we find that recently ejected outflow bullets produce a ‘Hubble wedge’ in the position–velocity relation. However, once such a bullet hits the leading shock front, it decelerates and aligns with older bullets to form a ‘Hubble-law’. Bullets can be identified as bumps in the mass–velocity relation, which can be fit with a power-law, dM/dυ RAD ∝υ −1.5 RAD dM/dυRAD∝υRAD−1.5 ⁠.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Advanced Research Computing @ Cardiff (ARCCA)
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 9 January 2019
Date of Acceptance: 30 November 2018
Last Modified: 24 Apr 2020 15:30

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