SMA observations of the W3(OH) complex: Dynamical differentiation between W3(H<sub>2</sub>O) and W3(OH)

Qin, Sheng-Li; Schilke, P.; Wu, Jingwen; Wu, Yuefang; Sánchez-Monge, Á.; Liu, Ying

doi:10.1093/mnras/stv2801

Cited by 27 publications

(36 citation statements)

References 60 publications

(101 reference statements)

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“…In previous studies, the infall velocities of the host clumps were about 10 −1 to 10 0 km s −1 (e.g. Rygl et al 2013;Qin et al 2016). Most of our results fall within this range, with the median value of 0.91 km s −1 .…”

Section: Physical Propertiessupporting

confidence: 77%

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates

Yang,

Jiang,

Chen

et al. 2020

Preprint

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Gravitational accretion accumulates the original mass, and this process is crucial for us to understand the initial phases of star formation. Using the specific infall profiles in optically thick and thin lines, we searched the clumps with infall motion from the Milky Way Imaging Scroll Painting (MWISP) CO data in previous work. In this study, we selected 133 sources of them as a sub-sample for further research and identification. The excitation temperatures of these sources are between 7.0 and 38.5 K, while the H 2 column densities are between 10 21 and 10 23 cm −2 . We have observed optically thick lines HCO + (1-0) and HCN (1-0) using the DLH 13.7-m telescope, and found 56 sources of them with blue profile and no red profile in these two lines, which are likely to have infall motions, with the detection rate of 42%. It suggests that using CO data to restrict sample can effectively improve the infall detection rate. Among these confirmed infall sources, there are 43 associated with Class 0/I young stellar objects (YSOs), and 13 are not. These 13 sources are probably associated with the sources in earlier evolutionary stage. By comparison, the confirmed sources which are associated with Class 0/I YSOs have higher excitation temperatures and column densities, while the other sources are colder and have lower column densities. Most infall velocities of the sources we confirmed are between 10 −1 to 10 0 km s −1 , which is consistent with previous studies.

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Section: Physical Propertiessupporting

confidence: 77%

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates

Yang,

Jiang,

Chen

et al. 2020

Preprint

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“…In Qin et al (2016), they conclude that this region is undergoing global collapse, but W3(OH) contains an expanding HII region, whereas W3(H 2 O) contains a young stellar object that is accreting material but also has an outflow. This is similar to G35.20, but on a larger scale (the separation between these two sources is ∼7000 AU).…”

Section: Comparison To Other Hot Coresmentioning

confidence: 99%

“…The chemical differentiation between W3(OH) and W3(H 2 O) (Wyrowski et al 1999b) shows that the latter is a strong N-bearing source with various complex organics, but the former only contains a handful of O-bearing species (both contain CH 3 CN). In Qin et al (2016), they conclude that this region is undergoing global collapse, but W3(OH) contains an expanding HII region, whereas W3(H 2 O) contains a young stellar object that is accreting material but also has an outflow. This is similar to G35.20, but on a larger scale (the separation between these two sources is ∼7000 AU).…”

Section: Comparison To Other Hot Coresmentioning

confidence: 99%

Chemical segregation in hot cores with disk candidates

Allen

Tak

Sánchez-Monge³

et al. 2017

A&A

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Context. In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO. It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars. Aims. We investigate the chemical make up of several hot molecular cores to determine physical and chemical structure. We use high spectral and spatial resolution sub-millimeter observations to determine how this stage fits into the formation sequence of a high mass star. Methods. The sub-millimeter interferometer ALMA (Atacama Large Millimeter Array) was used to observe the G35.20-0.74N and G35.03+0.35 hot cores at 350 GHz in Cycle 0. We analyzed spectra and maps from four continuum peaks (A, B1, B2 and B3) in G35.20-0.74N, separated by 1000-2000 AU, and one continuum peak in G35.03+0.35. We made all possible line identifications across 8 GHz of spectral windows of molecular emission lines down to a 3σ line flux of 0.5 K and determined column densities and temperatures for as many as 35 species assuming local thermodynamic equilibrium (LTE). Results. In comparing the spectra of the four continuum peaks, we find each has a distinct chemical composition expressed in over 400 different transitions. In G35.20, B1 and B2 contain oxygen-and sulfur-bearing organic and inorganic species but few nitrogenbearing species whereas A and B3 are strong sources of O-, S-, and N-bearing organic and inorganic species (especially those with the CN-bond). Column densities of vibrationally excited states are observed to be equal to or greater than the ground state for a number of species. Deuterated methyl cyanide is clearly detected in A and B3 with D/H ratios of 8 and 13%, respectively, but is much weaker at B1 and undetected at B2. No deuterated species are detected in G35.03, but similar molecular abundances to G35.20 were found in other species. We also find co-spatial emission of isocyanic acid (HNCO) and formamide (NH 2 CHO) in both sources indicating a strong chemical link between the two species. Conclusions. The chemical segregation between N-bearing organic species and others in G35.20 suggests the presence of multiple protostars, surrounded by a disk or torus.

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“…Its most prominent, high-mass star forming sub-regions are W3(OH) and W3 Main (for an overview see e.g., Megeath et al 2008); in projection they are ∼10 pc apart. The archetypical ultracompact HII region W3(OH) (e.g., Qin et al 2016) is located at a distance of 2 kpc (Xu et al 2006;Hachisuka et al 2006). W3 Main contains several luminous infrared sources, out of which W3 IRS5, harboring a massive protocluster (Wang et al 2013), is the IR-brightest.…”

Section: Main Characteristics Of the Observed Sightlinesmentioning

confidence: 99%

Unveiling the chemistry of interstellar CH

Wiesemeyer

Güsten

Menten

et al. 2018

A&A

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Context. The methylidyne radical CH is commonly used as a proxy for molecular hydrogen in the cold, neutral phase of the interstellar medium. The optical spectroscopy of CH is limited by interstellar extinction, whereas far-infrared observations provide an integral view through the Galaxy. While the HF ground state absorption, another H2 proxy in diffuse gas, frequently suffers from saturation, CH remains transparent both in spiral-arm crossings and high-mass star forming regions, turning this light hydride into a universal surrogate for H2. However, in slow shocks and in regions dissipating turbulence its abundance is expected to be enhanced by an endothermic production path, and the idea of a “canonical” CH abundance needs to be addressed. Aim. The N = 2 ← 1 ground state transition of CH at λ149 μm has become accessible to high-resolution spectroscopy thanks to the German Receiver for Astronomy at Terahertz Frequencies (GREAT) aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Its unsaturated absorption and the absence of emission from the star forming regions makes it an ideal candidate for the determination of column densities with a minimum of assumptions. Here we present an analysis of four sightlines towards distant Galactic star forming regions, whose hot cores emit a strong far-infrared dust continuum serving as background signal. Moreover, if combined with the sub-millimeter line of CH at λ560 μm , environments forming massive stars can be analyzed. For this we present a case study on the “proto-Trapezium” cluster W3 IRS5. Methods. While we confirm the global correlation between the column densities of HF and those of CH, both in arm and interarm regions, clear signposts of an over-abundance of CH are observed towards lower densities. However, a significant correlation between the column densities of CH and HF remains. A characterization of the hot cores in the W3 IRS5 proto-cluster and its envelope demonstrates that the sub-millimeter/far-infrared lines of CH reliably trace not only diffuse but also dense, molecular gas. Results. In diffuse gas, at lower densities a quiescent ion-neutral chemistry alone cannot account for the observed abundance of CH. Unlike the production of HF, for CH+ and CH, vortices forming in turbulent, diffuse gas may be the setting for an enhanced production path. However, CH remains a valuable tracer for molecular gas in environments reaching from diffuse clouds to sites of high-mass star formation.

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

Cited by 27 publications

References 60 publications

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates

Chemical segregation in hot cores with disk candidates

Unveiling the chemistry of interstellar CH

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

Cited by 27 publications

References 60 publications

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates

In Search for Infall Motion in molecular clumps II: HCO+ (1-0) and HCN (1-0) Observations toward a Sub-sample of Infall Candidates

Chemical segregation in hot cores with disk candidates

Unveiling the chemistry of interstellar CH

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