Chemical templates of the Central Molecular Zone

Context . The Central Molecular Zone (CMZ) of the Milky Way exhibits extreme conditions, including high gas densities, elevated temperatures, enhanced cosmic-ray ionization rates, and large-scale dynamics. This makes it a perfect laboratory for astrochemical studies. With large-scale molecular surveys revealing increasing chemical and physical complexity in the CMZ, it is essential to develop robust methods to decode the chemical information embedded in this extreme region. Aims . A key step to interpreting the molecular richness found in the CMZ is building chemical templates tailored to its diverse conditions. In particular, understanding how CMZ environments affect shock and protostellar chemistry is crucial. The combined impact of high ionization, elevated temperatures, and dense gas remains insufficiently explored for observable tracers. Methods . For this study, we utilized UCLCHEM , a gas-grain time-dependent chemical model, to link physical conditions with their corresponding molecular signatures and identify key tracers of temperature, density, ionization, and shock activity. To achieve this, we ran a grid of models of shocks and protostellar objects representative of typical CMZ conditions, focusing on 24 species, including complex organic molecules. Results . Shocked and protostellar environments show distinct evolutionary timescales (≲10 4 vs. ≳10 4 years); 300 K emerges as a key temperature threshold for chemical differentiation. We find that cosmic-ray ionization and temperature are the main drivers of chemical trends. HCO + , H 2 CO, and CH 3 SH trace ionization, while HCO, HCO + , CH 3 SH, CH 3 NCO, and HCOOCH 3 show consistent abundance contrasts between shocks and protostellar regions over similar temperature ranges. Conclusions . We characterized the behavior of 24 species in protostellar and shock-related environments. While our models underpredict some complex organics in shocks, they reproduce observed trends for most species, supporting scenarios involving a need for recurring shocks in Galactic Center clouds and enhanced ionization toward Sgr B2(N2). Future work should assess the role of shock recurrence and metallicity in shaping chemistry.

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Journal
Astronomy and Astrophysics
Published
2025-09-12
DOI
https://doi.org/10.1051/0004-6361/202556188
Primary Topic
Molecular Spectroscopy and Structure
Type
article
Field-Weighted Citation Impact
0.00

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article

Chemical templates of the Central Molecular Zone

Thanja Lamberts, J. Ott, Jairo Armijos-Abendaño, Shaoshan Zeng et al.
Astronomy and Astrophysics
Molecular Spectroscopy and Structure
article

Chemical templates of the Central Molecular Zone

Thanja Lamberts, J. Ott, Jairo Armijos-Abendaño, Shaoshan Zeng, Laura Colzi, Yue Hu, J. E. Pineda, A. Schmiedeke, V. M. Rivilla, Laura A. Busch, Miriam G. Santa-Maria, K. M. Dutkowska, Á. Sánchez-Monge, S. Martín, Elisabeth A. C. Mills, Lu Xing, Steven N. Longmore, S. Viti, Gijs Vermariën, Kevin M. Smith, Pablo García, C. Henkel, Izaskun Jiménez-Serra, Fengwei Xu
article en

Abstract

Context . The Central Molecular Zone (CMZ) of the Milky Way exhibits extreme conditions, including high gas densities, elevated temperatures, enhanced cosmic-ray ionization rates, and large-scale dynamics. This makes it a perfect laboratory for astrochemical studies. With large-scale molecular surveys revealing increasing chemical and physical complexity in the CMZ, it is essential to develop robust methods to decode the chemical information embedded in this extreme region. Aims . A key step to interpreting the molecular richness found in the CMZ is building chemical templates tailored to its diverse conditions. In particular, understanding how CMZ environments affect shock and protostellar chemistry is crucial. The combined impact of high ionization, elevated temperatures, and dense gas remains insufficiently explored for observable tracers. Methods . For this study, we utilized UCLCHEM , a gas-grain time-dependent chemical model, to link physical conditions with their corresponding molecular signatures and identify key tracers of temperature, density, ionization, and shock activity. To achieve this, we ran a grid of models of shocks and protostellar objects representative of typical CMZ conditions, focusing on 24 species, including complex organic molecules. Results . Shocked and protostellar environments show distinct evolutionary timescales (≲10 4 vs. ≳10 4 years); 300 K emerges as a key temperature threshold for chemical differentiation. We find that cosmic-ray ionization and temperature are the main drivers of chemical trends. HCO + , H 2 CO, and CH 3 SH trace ionization, while HCO, HCO + , CH 3 SH, CH 3 NCO, and HCOOCH 3 show consistent abundance contrasts between shocks and protostellar regions over similar temperature ranges. Conclusions . We characterized the behavior of 24 species in protostellar and shock-related environments. While our models underpredict some complex organics in shocks, they reproduce observed trends for most species, supporting scenarios involving a need for recurring shocks in Galactic Center clouds and enhanced ionization toward Sgr B2(N2). Future work should assess the role of shock recurrence and metallicity in shaping chemistry.

Astronomy and AstrophysicsVol. 703
Leiden University (NL), University of Bonn (DE), Pioneer (United States) (US), University of Kansas (US), National Radio Astronomy Observatory (US), Atacama Large Millimeter Submillimeter Array (CL), Shanghai Astronomical Observatory (CN), Universidad Católica del Norte (CL), University of Florida (US), Max Planck Institute for Extraterrestrial Physics (DE), Institute of Space Sciences (ES), Centro de Astrobiología (ES), Astronomy and Space (AU), Spanish National Observatory (ES), Max Planck Institute for Radio Astronomy (DE), National Astronomical Observatories (CN), University College London (GB), Liverpool John Moores University (GB)
National Science Foundation, Natural Science Foundation of Shanghai, Ministerio de Ciencia, Innovación y Universidades, European Commission, National Natural Science Foundation of China, Chinese Academy of Sciences, Ministerio de Ciencia e Innovación, Consejo Superior de Investigaciones Científicas, European Regional Development Fund, Agencia Estatal de Investigación, European Social Fund
Openalex Percentile: Top 75%
Molecular Spectroscopy and Structure
DOIOpen Access PDFOpenAlex
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