Redshifted methanol absorption tracing infall motions of high-mass star formation regions

Yang, Wenjin; Menten, K. M.; Yang, A. Y.; Wyrowski, F.; Gong, Y.; Ellingsen, S. P.; Henkel, C.; Chen, X.; Xu, Yan

doi:10.1051/0004-6361/202142811

Cited by 4 publications

(1 citation statement)

References 117 publications

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“…Only a few studies have confirmed the 6.7 GHz line in absorption thus far (e.g. Menten 1991b; Pandian et al 2008;Impellizzeri et al 2008;Ortiz-León et al 2021;Yang et al 2022). Absorption in this line can occur towards radio continuum emission and the cosmic microwave background (CMB).…”

Section: Absorption Detectionsmentioning

confidence: 95%

A global view on star formation: The GLOSTAR Galactic plane survey

Nguyen

Rugel

Murugeshan

et al. 2022

A&A

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Class II methanol (CH 3 OH) masers are amongst the clearest signposts of recent high-mass star formation (HMSF). A complete catalogue outlines the distribution of star formation in the Galaxy, the number of young star-forming cores, and the physical conditions of their environment, made possible by the Global View on Star Formation (GLOSTAR) survey. This blind survey of the radio regime of 4-8 GHz maps the Galactic mid-plane in the radio continuum, 6.7 GHz methanol line, the 4.8 GHz formaldehyde line, and several radio recombination lines. We present an analysis of the observations of the 6.7 GHz CH 3 OH maser transition using data from the D-configuration of the Very Large Array (VLA). We analysed data covering Galactic longitudes from −2 • < l < 60 • and Galactic latitudes of |b| < 1 • . We detected a total of 554 methanol masers, out of which 84 are new, and we catalogued their positions, velocity components, and integrated fluxes. With a typical noise level of ∼18 mJy beam −1 , this is the most sensitive unbiased methanol survey for methanol masers to date. We also searched for dust continuum and radio continuum associations, finding that 97% of the sources are associated with dust and 12% are associated with radio continuum emission.

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Section: Absorption Detectionsmentioning

confidence: 95%

A global view on star formation: The GLOSTAR Galactic plane survey

Nguyen

Rugel

Murugeshan

et al. 2022

A&A

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ATLASGAL: 3 mm class I methanol masers in high-mass star formation regions

Yang¹,

Gong²,

Menten³

et al. 2023

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Context. Class I methanol masers are known to be associated with shocked outflow regions around massive protostars, indicating a possible link between the maser properties and those of their host clumps. Aims. The main goals of this study are (1) to search for new class I methanol masers, (2) to statistically study the relationship between class I masers and shock tracers, (3) to compare the properties between class I masers and their host clumps, also as a function of their evolutionary stage, and (4) to constrain the physical conditions that excite multiple class I masers simultaneously. Methods. We analysed the 3 mm wavelength spectral line survey of 408 clumps identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), which were observed with the IRAM 30-meter telescope, focusing on the class I methanol masers with frequencies near 84, 95, and 104.3 GHz. Results. We detect narrow maser-like features towards 54, 100, and 4 sources in the maser lines near 84, 95, and 104.3 GHz, respectively. Among them, 50 masers at 84 GHz, 29 masers at 95 GHz, and 4 rare masers at 104.3 GHz are new discoveries. The new detections increase the number of known 104.3 GHz masers from five to nine. The 95 GHz class I methanol maser is generally stronger than the 84 GHz maser counterpart. We find nine sources showing class I methanol masers, but no SiO emission, indicating that class I methanol masers might be the only signpost of protostellar outflow activity in extremely embedded objects at the earliest evolutionary stage. Class I methanol masers that are associated with sources that show SiO line wings are more numerous and stronger than those without such wings. The total integrated intensity of class I methanol masers is well correlated with the integrated intensity and velocity coverage of the SiO (2−1) emission. The properties of class I methanol masers are positively correlated with the bolometric luminosity, clump mass, and peak H2 column density of their associated clumps, but are uncorrelated with the luminosity-to-mass ratio, dust temperature, and mean H2 volume density. Conclusions. We suggest that the properties of class I masers are related to shocks traced by SiO. Based on our observations, we conclude that class I methanol masers at 84 and 95 GHz can trace a similar evolutionary stage to the H2O maser, and appear prior to 6.7 and 12.2 GHz methanol and OH masers. Despite their small number, the 104.3 GHz class I masers appear to trace a shorter and more evolved stage compared to the other class I masers.

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NH₃ (1,1) hyperfine intensity anomalies in infall sources

Wu,

Henkel,

Zhou

et al. 2024

A&A

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Identifying infall motions is crucial for our understanding of accretion processes in regions of star formation. The NH$_ $ $(1,1)$ hyperfine intensity anomaly (HIA) has been proposed to be a readily usable tracer for such infall motions in star-forming regions harboring young stellar objects at very early evolutionary stages. In this paper, we seek to study the HIA toward 15 infall candidate regions in order to assess its reliability as an infall tracer. Using deep observations of the NH$_ $ $(1,1)$ transition with the Effelsberg 100\,m telescope, we identified HIAs toward all 15 targets. Of the 15 sources, 14 exhibit anomalous intensities in either the inner or outer satellite lines. All the derived HIAs conform to the framework of the existing two models, namely hyperfine selective trapping (HST) and systematic contraction or expansion motion (CE) models. In our sample of infall candidates, the majority of the HIAs remain consistent with the HST model. Only in three targets are the HIAs consistent with infall motions under the CE model. Thus, the HIA could indeed be used as an infall tracer, but does not appear to be highly sensitive to infall motions in our single-dish data. Nevertheless, the emission could be blended with emission from outflow activities. HIAs consistent with the HST model show stronger anomalies with increasing kinetic temperatures K $), which is expected based on the HST model. On the other hand, HIAs consistent with infall motions show little dependence on $T_ K $. Therefore, HIAs may preferably trace the infall of cold gas.

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Redshifted methanol absorption tracing infall motions of high-mass star formation regions

Cited by 4 publications

References 117 publications

A global view on star formation: The GLOSTAR Galactic plane survey

A global view on star formation: The GLOSTAR Galactic plane survey

ATLASGAL: 3 mm class I methanol masers in high-mass star formation regions

NH₃ (1,1) hyperfine intensity anomalies in infall sources

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Redshifted methanol absorption tracing infall motions of high-mass star formation regions

Cited by 4 publications

References 117 publications

A global view on star formation: The GLOSTAR Galactic plane survey

A global view on star formation: The GLOSTAR Galactic plane survey

ATLASGAL: 3 mm class I methanol masers in high-mass star formation regions

NH3 (1,1) hyperfine intensity anomalies in infall sources

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NH₃ (1,1) hyperfine intensity anomalies in infall sources