Context: Jets and outflows are key ingredients in the formation of stars across the mass spectrum. In clustered regions, understanding powering sources and outflow components poses a significant problem. Aims: To understand the dynamics in the outflo
w(s) from a cluster in the process of forming massive stars. Methods: We use new VLA observations of the molecular gas (SiO, CS, OCS and molec) in the massive star forming region IRAS 17233-3606 which contains a number of HII regions. We compare these observations to previously published molecular data for this source in order to get a holistic view of the outflow dynamics. Results:We find that the dynamics of the various species can be explained by a single large scale ($sim 0.15$ pc) outflow when compared to the sizes of the HII regions, with the different morphologies of the blue and red outflow components explained with respect to the morphology of the surrounding envelope. We further find that the direction of the velocity gradients seen in OCS and molec are suggestive of a combination of rotation and outflow motions in the warm gas surrounding the HII regions near the base of the large scale outflow. Conclusions: Our results show that the massive protostars forming within this region appear to be contributing to a single outflow on large scales. This single large scale outflow is traced by a number of different species as the outflow interacts with its surroundings. On the small scales, there appear to be multiple mechanisms contributing to the dynamics which could be a combination of either a small scale outflow or rotation with the dynamics of the large scale outflow.
Whether high mass stars continue to accrete material beyond the formation of an HII region is still an open question. Ionized infall and outflow have been seen in some sources, but their ties to the surrounding molecular gas are not well constrained.
We aim to quantify the ionized and molecular gas dynamics in a high mass star forming region (K3-50A) and their interaction. We present CARMA observations of the 3mm continuum, H41alpha, and HCO+ emission, and VLA continuum observations at 23 GHz and 14.7 GHz to quantify the gas and its dynamics in K3-50A. We find large scale dynamics consistent with previous observations. On small scales, we find evidence for interaction between the ionized and molecular gas which suggests the ionized outflow is entraining the molecular one. This is the first time such an outflow entrained by photo ionized gas has been observed. Accretion may be ongoing in K3-50A because an ionized bipolar outflow is still being powered, which is in turn entraining part of the surrounding molecular gas. This outflow scenario is similar to that predicted by ionization feedback models.
Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated wi
th the farthest knots. Here we present ALMA Science Verification data of CO J=2-1 and J=3-2 emission which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km/s. The emission has a double corkscrew morphology and extends more than 10 from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet which is moving at much higher velocities. We show that the J=3-2 emission is likely heavily filtered by the interferometer, but the J=2-1 emission suffers less due to the larger beam and measurable angular scales. Excitation analysis suggests temperatures exceeding 900 K in these compact features, with the wind mass, momentum and energy being of order 10^{-5} M_sun, 10^{-4} M_sun km/s and 10^{40} erg respectively. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star.
(Context) Many physical parameters change with time in star forming regions. Here we attempt to correlate changes in infall and outflow motions in high mass star forming regions with evolutionary stage using JCMT observations. (Aims) From a sample of
45 high mass star forming regions in three phases of evolution, we investigate the presence of established infall and outflow tracers to determine whether there are any trends attributable to the age of the source. (Methods) We obtained JCMT observations of HCO+/H13CO+ J=4-3 to trace large scale infall, and SiO J=8-7 to trace recent outflow activity. We compare the infall and outflow detections to the evolutionary stage of the host source (high mass protostellar objects, hypercompact HII regions and ultracompact HII regions). We also note that the integrated intensity of SiO varies with the full width at half maximum of the H13CO+. (Results) We find a surprising lack of SiO detections in the middle stage (Hypercompact HII regions), which may be due to an observational bias. When SiO is detected, we find that the integrated intensity of the line increases with evolutionary stage. We also note that all of the sources with infall signatures onto Ultracompact HII regions have corresponding outflow signatures as well.
We present molecular line and 1.4 mm continuum observations towards five massive star forming regions at arcsecond resolution using the Submillimeter Array (SMA). We find that the warm molecular gas surrounding each HII region (as traced by SO_2 and
OCS) appears to be undergoing bulk rotation. From the molecular line emission and thermal component of the continuum emission, we independently derived gas masses for each region which are consistent with each other. From the free-free component of the continuum emission we estimate the minimum stellar mass required to power the HII region and find that this mass, when added to the derived gas mass, is a significant fraction of the dynamical mass for that region.
In order to distinguish between the various components of massive star forming regions (i.e. infalling, outflowing and rotating gas structures) within our own Galaxy, we require high angular resolution observations which are sensitive to structures o
n all size scales. To this end, we present observations of the molecular and ionized gas towards massive star forming regions at 230 GHz from the SMA (with zero spacing from the JCMT) and at 22 and 23 GHz from the VLA at arcsecond or better resolution. These observations (of sources such as NGC7538, W51e2 and K3-50A) form an integral part of a multi-resolution study of the molecular and ionized gas dynamics of massive star forming regions (i.e. Klaassen & Wilson 2007). Through comparison of these observations with 3D radiative transfer models, we hope to be able to distinguish between various modes of massive star formation, such as ionized or halted accretion (i.e Keto 2003 or Klaassen et al. 2006 respectively).
