Chemical templates of the Central Molecular Zone. Shock and protostellar object signatures under Galactic Center conditions

Dutkowska, KM, Vermariën, G, Viti, S, Jiménez-Serra, I, Colzi, L, Busch, LA, Rivilla, VM, Mills, EAC, Martín, S, Henkel, C, García, P, Lu, X, Santa-Maria, MG, Armijos-Abendaño, J, Hu, Y, Ott, J, Smith, K, Xu, F, Zeng, S, Sánchez-Monge, Á et al (2025) Chemical templates of the Central Molecular Zone. Shock and protostellar object signatures under Galactic Center conditions. Astronomy & Astrophysics, 703 (A46). pp. 1-22. ISSN 0004-6361

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Abstract

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. 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. 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. Shocked and protostellar environments show distinct evolutionary timescales (łesssim 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_2CO, and CH_3SH trace ionization, while HCO, HCO^+, CH_3SH, CH_3NCO, and HCOOCH_3 show consistent abundance contrasts between shocks and protostellar regions over similar temperature ranges. 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.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
Date of acceptance:	12 August 2025
Date of first compliant Open Access:	7 November 2025
Date Deposited:	07 Nov 2025 10:14
Last Modified:	07 Nov 2025 10:15
DOI or ID number:	10.1051/0004-6361/202556188
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27508

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