A study of high velocity molecular outflows with an up-to-date sample

By Yue-fang Wu, Y. Wei, Ming Zhao, Y. Shi, W. Yu, S. Qin, M. Huang. 2004

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A statistical study of the properties of molecular outflows is performed based on an up-to-date sample. 391 outflows were identified in published articles or preprints before February 28, 2003. The parameters of position, morphology, mass, energy, outflow dynamics and central source luminosity are presented for each outflow source. Outflow lobe polarity is known for all the sources, and 84% are found to be bipolar. The sources are divided into low mass and high mass groups according to either the available bolometric luminosity of the central source or the outflow mass. The pace of discovery of outflows over the past seven years has increased much more rapidly than in previous periods. Surveys for outflows are still continuing. The number of high-mass outflows detected (139) has considerably increased, showing that they are commonly associated with massive as well as low mass stars. Energetic mass ejection may be a common aspect of the formation of high mass as well as low mass stars. Outflow masses are correlated strongly with bolometric luminosity of the center sources, which was obtained for the first time. There are also correlations between the central source luminosity and the parameters of mechanical luminosity and the thrust or force necessary to drive the outflow. The results show that flow mass, momentum and energy depend on the nature of the central source. Despite their similarity, there are differences between the high mass and low mass outflows. Low mass outflows are more collimated than high mass outflows. On average, the mass of high mass sources can be more than two orders of magnitude larger than those of low mass outflows. The relation between flow mass and dynamical time appears to differ for the two types of outflows. Low mass sources make up 90% of outflows associated with HH objects while high mass outflows make up 61% of the sources associated with H 2 O masers. Sources with characteristics of collapse or infall comprise 12% of the entire outflow sample. The spatial distribution of the outflow sources in the Galaxy is presented and the local occurrence rate is compared with the stellar birth rate.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/ab5ddf1159560a87edd790747f721229ebd18101

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Citations in the corpus

THE PROPERTIES OF MASSIVE, DENSE CLUMPS: MAPPING SURVEYS OF HCN AND CS (2010, methodology): “To extend the sample towards lower luminosities for the study of L′HCN -LIR correlation, we selected 14 IRAS sources from outflow surveys (Zhang et al. 2005; Wu et al. 2004) and a few lower mass clumps from other publications.”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Magnetic fields plus rotation lead to winds and jets (Shang et al. 2007; Pudritz et al. 2007), which drive molecular outflows from young stars of essentially all masses (Arce et al. 2007; Wu et al. 2004).”
Connecting Dense Gas Tracers of Star Formation in our Galaxy to High-z Star Formation (2005, methodology): “To extend the sample towards lower luminosities, we selected 14 IRAS sources from outflow surveys (Zhang et al. 2005; Wu et al. 2004) and a few from other publications.”
Theory of Star Formation (2007, background): “Outflows from high-mass protostellar objects with L 105 L⊙ (corresponding to m∗ 25 M⊙—Arnett, 1996) are collimated (Beuther et al., 2002b), but somewhat less so than those in low-mass protostars (Wu et al., 2004).”
High- and Low-Velocity Magnetized Outflows in the Star Formation Process in a Gravitationally Collapsing Cloud (2008, background): “During star formation, neither radiation nor thermal pressure from the protostar can supply sufficient kinetic energy and momentum for driving the outflow and the jet (Wu et al. 2004; Pudritz et al. 2007).”