Widespread Methanol Maser Emission Detected at Galactic Center's Bar-CMZ Interface
Astronomers have detected widespread Class I methanol maser emission at Galactic longitude l=1.3, where gas inflowing along the Milky Way's bar structure collides with the Central Molecular Zone. The masers, observed at 36.2 GHz and 44.1 GHz using the Yebes 40m telescope, are associated with shock-processed gas in a kinematically complex region extending several parsecs. The findings suggest large-scale galactic bar dynamics can trigger maser activity and offer a Galactic analogue for similar phenomena observed in the nuclear regions of other barred galaxies.
A team of researchers has identified widespread Class I methanol (CH3OH) maser emission at the interface between the Milky Way's bar-driven dust lane inflow and the Central Molecular Zone (CMZ), near Galactic longitude l=1.3. Using the Yebes 40m radio telescope, the team detected multiple 36.2 GHz masers and two candidate 44.1 GHz masers spread across a region of several parsecs, with the brightest maser reaching an isotropic luminosity of approximately 0.9×10⁻³ solar luminosities — placing it among the most luminous known Galactic Class I masers. Complementary data from the Herschel-HiGAL and CHIMPS2 surveys revealed enhanced fractional abundances of thermal CH3OH and SiO emission across a mapped area of roughly 24 parsecs, consistent with shock-processed gas. CO position-velocity analysis tied the masers to an extended velocity feature at VLSR ~100 km/s, supporting a bar-CMZ interface origin. The study concludes that large-scale gas dynamics, rather than local star formation alone, are the primary driver of the maser activity, though some masers may also trace shocks from nearby star-forming regions. The authors propose this region serves as a valuable Galactic-scale laboratory for understanding how bar-driven inflows shape star formation and maser environments in barred spiral galaxies more broadly. The paper has been accepted for publication in Astronomy & Astrophysics.
What's missing
The study notes that disentangling the relative contributions of large-scale bar-driven shocks versus local star-formation-driven shocks to individual masers remains uncertain. Higher angular resolution follow-up observations would be needed to spatially resolve and attribute individual maser spots to specific physical mechanisms. The paper also does not yet include interferometric confirmation of all candidate masers, which could affect the classification of the two 44.1 GHz candidates.
What different sources said
- arXiv astro-phCenter
Class I CH3OH Maser Emission from Bar-Driven Inflow Colliding with the Central Molecular Zone
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