The Rotating Molecular Structures and the Ionized Outflow Associated With Iras 16547–4247

Abstract

We present Very Large Array 1.3 cm radio continuum and water maser observations as well as Submillimeter Array SO 2 (226.300 GHz) and 1.3 mm dust continuum observations toward the massive star formation region IRAS 16547−4247. We find evidence of multiple sources in the central part of the region. There is evidence of a rotating structure associated with the most massive of these sources, traced at small scales (∼50 AU) by the water masers. At large scales (∼1000 AU), we find a velocity gradient in the SO 2 molecular emission with a barely resolved structure that can be modeled as a rotating ring or two separate objects. The velocity gradients of the masers and of the molecular emission have the same sense and may trace the same structure at different size scales. The position angles of the structures associated with the velocity gradients are roughly perpendicular to the outflow axis observed in radio continuum and several molecular tracers. We estimate the mass of the most massive central source to be around 30 solar masses from the velocity gradient in the water maser emission. The main source of error in this estimate is the radius of the rotating structure. We also find water masers that are associated with the large-scale molecular outflow of the system, as well as water masers that are associated with other sources in the region. Our results suggest that the formation of this source, one of the most luminous protostars or protostellar clusters known, is taking place with the presence of ionized jets and disk-like structures.

Iras 16547–4247: A New Candidate of a Protocluster Unveiled With Alma

“…Our observations also support the existence of another source as suggested by Rodríguez et al (2008). For discussion, we also plot the positions of the H 2 O (g1 and g2 in Figure 2(a)) and CH 3 OH maser clusters (pink crosses in Figure 4) detected by Franco-Hernández et al (2009) and Voronkov et al (2006), respectively.…”

“…The contours for integrated intensity maps, with intervals of 3σ , start from the 3σ level (1σ = 0.6 Jy beam −1 km s −1 for both blueshifted and redshifted gas). The black cross marks the position of the water masers called S1 in Franco-Hernández et al (2009). The grayscale bar shows the flux density of dust continuum emission.…”

“…Garay et al (2007) identified a large-scale bipolar 12 CO(J = 3-2) outflow, which is roughly oriented in the north-south direction and centered at the position of the jet source. Franco-Hernández et al (2009) reported 1.3 mm dust continuum and SO 2 observations made with the Submillimeter Array (SMA). They found that the SO 2 emission traces a small molecular structure associated with the jet exhibiting a velocity gradient and proposed the existence of Keplerian rotation.…”

A near-infrared spectroscopic survey of massive jets towards extended green objects

“…H 2 O masers were detected towards the source position (Batchelor et al 1980). SMA observations at a higher spatial resolution show that water maser emission is present in several distinct parts of the region (Franco-Hernández et al 2009). In particular, a compact structure located at the disc position and perpendicular to the radio jet shows a velocity gradient possibly arising from Keplerian motion, which would imply a mass of ∼30 M for the central star(s).…”

“…The source is not detected in our NIR images or in the Spitzer/IRAC images, although it is visible as a single object in the Spitzer/MIPS images at 24 μm. At high spatial resolution, Submillimeter Array (SMA) observations of the dust continuum at 1.3 mm (Franco-Hernández et al 2009) trace a more complex structure, indicating that there might be at least two objects. H 2 O masers were detected towards the source position (Batchelor et al 1980).…”