Search for CO Outflows toward a Sample of 69 High‐Mass Protostellar Candidates. II. Outflow Properties

Abstract

We present a study of molecular outflows toward a sample of 69 luminous IRAS point sources. The sample is associated with dense molecular gas and has far-infrared luminosities ranging from 10 2 to 10 5 L , indicating these objects as regions likely forming high-mass stars. Mapping in the CO J ¼ 2 1 line shows that molecular outflows are ubiquitous in these regions. Most of the outflows have masses of tens of M . The typical dynamical timescale of the flow, without correcting for inclination of the flow axis, is a few times 10 4 yr. The typical energy in the outflows is 10 46 ergs, comparable to the turbulent energy in the core. Nearly half of the outflows show spatially resolved bipolar lobes. This indicates that low-mass young stars that coexist in the region are not responsible for the bipolar outflows observed. It is the more massive stars that drive the outflow. The large detection rate of outflows in the region favors an accretion process in the formation of massive stars. The maximum mass-loss rate in the wind is about 10 À4 M yr À1 . If these outflows are driven via accretion, the accretion rate should be as high as a few times 10 À4 M yr À1

SMA observations of the W3(OH) complex: Dynamical differentiation between W3(H2O) and W3(OH)

“…Therefore, episodic and precessing outflows in the W3(H 2 O) might be related to the presence of a binary system. The lack of an Hii region in W3(H 2 O), the presence of strong dust emission and the derived short outflow timescale of (5.6±0.2)×10 3 yr, compared with other high-mass molecular outflows (e. g., Beuther et al 2002;Wu et al 2004;Zhang et al 2005;Sánchez-Monge et al 2013b), suggest that the W3(H 2 O) could be in an early evolutionary stage of the high-mass star formation process. Spectral infall signatures are seen in W3(H 2 O), and an unusually large spherical mass infall rate of (2.3±0.7)×10 −3 M ⊙ yr −1 is derived.…”

“…For high-mass stars, their formation process is still not well understood. Outflows are frequently detected in high-mass star forming regions, but it is thought that high-mass star formation is not merely a scaled-up version of the low-mass star formation process characterized by larger outflow parameters (e. g., Wu et al 2004), poor collimation around massive young stars (e. g., Shepherd & Churchwell 1996;Zhang et al 2005) and higher accretion rates (see review by Zinnecker & Yorke 2007). Additionally, disks in high-mass young stellar objects are still elusive -only a few of them have been detected (Zhang ⋆ E-mail: slqin@bao.ac.cn Shepherd, Claussen & Kurtz 2001;Patel et al 2005;Jiang et al 2005;Sánchez-Monge et al 2013a -probably due to their short lifetimes, the necessity of achieving high angular resolution (not available in the observations prior to ALMA) and source confusion in dense clusters.…”

Radio and infrared study of the star-forming region IRAS 20286+4105

“…IRAS 20286+4105 also forms part of the Balloonborne Large Aperture Submillimeter Telescope (BLAST) survey of the Cygnus region at 250, 350 and 500 µm (Roy et al 2011). Based on the near-infrared (NIR) H2 line maps, Varricatt et al (2010) have identified two outflows, the positions of which are consistent with the CO outflow results of Zhang et al (2005). IRAS 20286+4105 has also been the target of many surveys to detect masers.…”

Absolute positions of 6.7-GHz methanol masers

“…Columns (9)-(11) present the distance from the Galactic center, and the far and near kinematic distances. References for the velocities: 1 - Zhang et al (2005); 2 - Larionov et al (1999);3 -Szymczak et al (2007);4 -van der Walt et al (2007).…”