Class I CH

Springer Link (Chiba Institute of Technology)

Abstract

Context. The central molecular zone (CMZ) of the Milky Way is shaped by the interplay of bar-driven inflows, shocks, and star formation. It has been proposed that at a Galactic longitude of l = 1.3° gas inflowing along the near-side dust lane interacts with the CMZ boundary and overshoots into the region above the Galactic plane, making this a key site for investigating how large-scale gas dynamics regulates star formation. Aims. We aim to investigate the presence of Class I methanol maser emission in this transitional region, testing whether large-scale gas interactions in the CMZ can trigger widespread maser activity via star formation or shocks. Methods. We conducted a dedicated search for the 36.2 and 44.1 GHz Class I CH3OH maser lines, along with the 48.4 GHz thermal transition, using the Yebes 40m telescope. We complemented these data with archival data from the Herschel-HiGAL survey and the CHIMPS2 survey to explore links between masers, shocks, and star formation. Results. We detect widespread 36.2 GHz maser emission and two candidate 44.1 GHz masers in a region extending several parsecs. The brightest 36.2 GHz maser has an isotropic luminosity of 0.9 × 10−3 L⊙, placing it among the most luminous Galactic Class I masers. Thermal CH3OH emission and SiO (1-0) emission extend over a mapped area of ~24 pc, with both species showing enhanced fractional abundances relative to H2. CO(3–2) position–velocity analysis further shows that the masers are associated with an extended velocity feature (EVF) at VLSR ~100 km s−1. Conclusions. We conclude that the observed masers are primarily associated with shock-processed gas in a kinematically complex bar–CMZ interface region. Large-scale gas interactions are likely to play an important role in producing the maser emission, although a subset of the masers may also be linked to shocks driven by local star formation activity. This region therefore provides a promising Galactic analogue of shock-dominated Class I CH3OH maser environments observed in nuclear regions of barred galaxies.

Authors 12

1. V. S. Veena

   Tata Institute of Fundamental Research · Max Planck Institute for Radio Astronomy

   Affiliation as printed

   Department of Astronomy & Astrophysics , Tata Institute of Fundamental Research , Homi Bhabha Road , Mumbai 400005 , India

   Max Planck Institute for Radioastronomy (MPIfR) , Auf dem Hügel 69 , 53121 Bonn , Germany

2. W.-J. Kim

   Max Planck Institute for Radio Astronomy

   Affiliation as printed

   Max Planck Institute for Radioastronomy (MPIfR) , Auf dem Hügel 69 , 53121 Bonn , Germany

3. P. Schilke

   University of Cologne

   Affiliation as printed

   I. Physikalisches Institut , Universität zu Köln , Zülpicher Str. 77 , 50937 Köln , Germany

4. Á. Sánchez-Monge

   Institute of Space Sciences · Institut d'Estudis Espacials de Catalunya

   Affiliation as printed

   Institut d'Estudis Espacials de Catalunya (IEEC) , Barcelona , Spain

   Institut de Ciències de l'Espai (ICE , CSIC) , Carrer de Can Magrans s/n , E-08193 , Bellaterra , Barcelona , Spain

5. C. Henkel

   Max Planck Institute for Radio Astronomy

   Affiliation as printed

   Max Planck Institute for Radioastronomy (MPIfR) , Auf dem Hügel 69 , 53121 Bonn , Germany

6. S. Viti Aachen Leiden Observatory

   Leiden University · University of Bonn · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , PO Box 9513 , 2300 RA Leiden , The Netherlands

   Transdisciplinary Research Area (TRA ) 'Matter'/Argelander-Institut für Astronomie , University of Bonn

7. Gisela B. Esplugues

   Spanish National Observatory

   Affiliation as printed

   Observatorio Astronómico Nacional (OAN , IGN) , Alfonso XII , 3 , 28014 Madrid , Spain

8. F. Wyrowski

   Max Planck Institute for Radio Astronomy

   Affiliation as printed

   Max Planck Institute for Radioastronomy (MPIfR) , Auf dem Hügel 69 , 53121 Bonn , Germany

9. W. E. Banda-Barragan

   Universität Hamburg · Universidad Yachay Tech

   Affiliation as printed

   Escuela de Ciencias Físicas y Nanotecnología , Universidad Yachay Tech , Hacienda San José S/N , 100119 Urcuquí , Ecuador

   Hamburger Sternwarte , University of Hamburg , Gojenbergsweg 112 , 21029 Hamburg , Germany

10. M. C. Sormani

    University of Insubria

    Affiliation as printed

    Como Lake centre for AstroPhysics (CLAP) , DiSAT , Università dell'Insubria , via Valleggio 11 , 22100 Como , Italy

11. D. Riquelme

    University of La Serena

    Affiliation as printed

    Departamento de Astronomía , Universidad de La Serena , Av. Cisternas 1200 , La Serena , Chile

12. G. A. Fuller

    University of Manchester

    Affiliation as printed

    Jodrell Bank Centre for Astrophysics , Department of Physics and Astronomy , The University of Manchester , Manchester M13 9PL , UK