Digging into the Massive Protostar S255IR NIRS3: A Study of Nitrogen-Bearing Molecules and Their Prebiotic Chemistry

2026/05/26 by Arijit Manna, Sabyasachi Pal, Tapas Baug +4 · 1 voice
Physics and Astronomy · #astro-ph.GA #physics.chem-ph

paper · pdf · doi:10.3847/1538-3881/ae64f2

Abstract

The study of complex nitrogen (N)-bearing molecules is essential for probing the physical and chemical evolution of star-forming regions. In this paper, we present the identification of rotational emission lines from several complex N-bearing species such as methyl cyanide (CH₃CN), ethyl cyanide (C₂H₅CN), vinyl cyanide (C₂H₃CN), cyanamide (NH₂CN), and formamide (NH₂CHO) toward the high-mass protostar S255IR NIRS3 using ALMA band 4 observations. In addition, the vibrationally excited transitions of cyanoacetylene (HC₃N, ν₇ = 2) were detected. The column densities and excitation temperatures of these molecules were derived through LTE spectral modelling, yielding excitation temperatures in the range of 175-220 K. The high excitation temperatures (175-220 K) indicate that the identified N-bearing molecules arise from the warm inner regions (T ≥ 100 K) of the source. The fractional abundances were further estimated relative to H₂, CH₃OH, and CH₃CN. A Pearson correlation heat map of the abundances reveals a strong positive correlation (r > 0.7) among three molecules in the cyanide family, such as CH₃CN, C₂H₃CN, and C₂H₅CN, suggesting that these N-bearing molecules may be chemically linked. Comparison with three-phase warm-up chemical models shows that the observed abundances of CH₃CN, C₂H₅CN, C₂H₃CN, NH₂CN, NH₂CHO, and HC₃N (ν₇ = 2) relative to H₂ are consistent with model predictions within factors of 1.04, 0.67, 1.28, 0.76, 0.72, and 0.96, respectively. Finally, we discuss the potential formation pathways of the identified N-bearing molecules in the context of gas-grain chemistry within S255IR NIRS3.

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Discussions

• Digging into the Massive Protostar S255IR NIRS3: A Study of Nitrogen-Bearing Molecules and Their Prebiotic Chemistry Manna et al. arXiv (AJ) arxiv.org/abs/2605.27177 [bsky, 0 points, 0 comments]

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