Infall and Outflow Detections in a Massive Core JCMT 18354–0649s

Abstract

We present a high-resolution study of a massive dense core JCMT 18354−0649S with the Submillimeter Array. The core is mapped with continuum emission at 1.3 mm and molecular lines including CH 3 OH (5 23 -4 13 ) and HCN (3-2). The dust core detected in the compact configuration has a mass of 47 M and a diameter of 2 (0.06 pc), which is further resolved into three condensations with a total mass of 42 M under higher spatial resolution. The HCN (3-2) line exhibits an asymmetric profile consistent with infall signature. The infall rate is estimated to be 2.0 × 10 −3 M yr −1 . The high-velocity HCN (3-2) line wings present an outflow with three lobes. Their total mass is 12 M and the total momentum is 121 M km s −1 . Analysis shows that the N-bearing molecules especially HCN can trace both inflow and outflow.

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

“…Therefore, the study and characterization of the outflow and infall processes involved in the formation of high-mass stars need to be understood in more detail. Since high-mass stars form in dense cores, dense gas tracers such as HCN are useful in identifying outflow and infall motions (e. g., Liu et al 2011aLiu et al , 2011bLiu et al , 2013Liu et al , 2015Wu et al 2005). It has also been demonstrated that the profile of spectral lines such as and HCO + (3-2) are good tools to search for and study the infall motions (see simulations by Smith et al 2012Smith et al , 2013and Chira et al 2014).…”

A Massive Protostar Embedded in the Scuba Core JCMT 18354-0649s

“…Spectral line observations of high-density tracers, including HCN(3-2), HCO + (3-2), H 13 CO + (3-2), and C 17 O(2-1), reveal a prominent blue profile (Wu et al 2005), which was confirmed with the Submillimeter Array (SMA) observations (Liu et al 2011), indicating that this core is collapsing. In addition, at the full width zero intensity (FWZI) level the HCN(3-2) and CO(3-2) line profiles span 38 km s −1 (Wu et al 2005), indicating outflow motions in this region.…”

“…The extended taillike feature may be the partially resolved counterpart of IRS1b, judging from its IRAC color. However, we cannot completely rule out the existence of shocked gas surrounding the protostars, as outflows are clearly seen on the HCN(3-2) map from the SMA (Liu et al 2011). If part of the extended emissions are indeed from shocked gas, the measured fluxes at 4.5 μm (and possibly at 5.8 μm) should be used as upper limits.…”

“…Thus, it is possible that the dust outside the 15 beam of our 850 μm observations is externally heated, presumably by G25.4NW (this also implies that J18354S is at the same radial distance as G25.4NW; see the discussion in Section 4.2). Moreover, the recently published SMA map of the dust emission at 1.3 mm shows that IRS1a is located at the edge of the major dust clump MM1 (see Figure 1 in Liu et al 2011). It is possible that a star is forming in the outer part of the core and heating up the gas in the surrounding envelope, but the majority of the dust is still cold.…”

“…More data are needed to determine the SED and mass of IRS1a and 1b. Nevertheless, the high-resolution interferometric maps at the HCN(3-2) transition clearly show that IRS1a is located at the center of the blueshifted and redshifted lobes of the outflow contours (see Figure 7 of Liu et al 2011), and most of the dust and CH 3 OH emission are associated with IRS1a rather than IRS1b (see Figures 1 and 2 of Liu et al 2011). Thus, we assume that IRS1a is the major source heating the nearby dust and driving the outflow in J18354S.…”