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

Yang, W., Gong, Y., Menten, K.M., Urquhart, J.S., Henkel, C., Wyrowski, F., Csengeri, T., Ellingsen, S.P., Bemis, A.R., Jang, J. and others. (2023) ATLASGAL: 3-mm class I methanol masers in high-mass star formation regions. Astronomy & Astrophysics, 675 . Article Number A112. ISSN 0004-6361. (doi:0.1051/0004-6361/202346227) (KAR id:101209)


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 analyzed the 3-mm wavelength spectral line survey of 408 ATLASGAL clumps observed with the IRAM 30m-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, fifty 84 GHz masers, twenty nine 95 GHz masers and four rare 104.3 GHz masers are new discoveries. The new detections increase the number of known 104.3 GHz masers from 5 to 9. The 95 GHz class I methanol maser is generally stronger than the 84 GHz maser counterpart. We find 9 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, peak H2 column density of their associated clumps but 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 as 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 short and more evolved stage compared to the other class I masers.

Item Type: Article
DOI/Identification number: 0.1051/0004-6361/202346227
Uncontrolled keywords: masers; star: formation; ISM: molecules; radio lines: ISM
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Funders: University of Kent (
Depositing User: James Urquhart
Date Deposited: 09 May 2023 11:52 UTC
Last Modified: 19 Sep 2023 15:41 UTC
Resource URI: (The current URI for this page, for reference purposes)

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