Carbon Chain Diversity In L1544 And IRAS 16293-2422: An Astrochemical Pathfinder Study For The SKAO

Astrochemical observations have revealed a surprisingly high level of chemical complexity, including long carbon chains, in the earliest stages of Sun-like star formation.

The origin of these species and whether they undergo further growth, possibly contributing to the molecular complexity of planetary systems, remain open questions. We present recent observations performed using the 100-m Green Bank Telescope of the prestellar core L1544 and the protostellar system IRAS 16293-2422.

In L1544, we detected several complex carbon-bearing species, including C2S, C₃S, C₃N, c-C₃H, C₄H, and C₆H, complementing previously reported emission of cyanopolyynes. In IRAS 16293-2422, we detected c-C₃H and, for the first time, HC₇N. Thanks to the high spectral resolution, we refine the rest frequencies of several c-C₃H and C₆H transitions.

We perform radiative transfer analysis, highlighting a chemical difference between the two sources: IRAS 16293-2422 shows column densities 10-100 times lower than L1544. We perform astrochemical modeling, employing an up-to-date chemical network with revised reaction rates.

The models reproduce the general trends, with cyanopolyyne and polyynyl radical abundances decreasing as molecular size increases, but they underestimate the abundances of cyanopolyynes longer than HC₅N by up to two orders of magnitude. Current models, which include the dominant neutral-neutral formation routes, cannot account for this discrepancy, suggesting that the chemical network is incomplete.

We propose that additional ion-molecule reactions are crucial for the formation of these species. Developing a more comprehensive chemical network for long carbon chains is essential for accurately interpreting present and future observations.

Lisa Giani, Eleonora Bianchi, Anthony Remijan, Claudio Codella, Giovanni Sabatini, Linda Podio, Cecilia Ceccarelli, Marta De Simone, Nadia Balucani, Paola Caselli, Eric Herbst, Francois Lique, Silvia Spezzano, Charlotte Vastel, Brett McGuire

Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2602.14804 [astro-ph.GA] (or arXiv:2602.14804v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2602.14804
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Journal reference: Monthly Notices of the Royal Astronomical Society, Volume 544, Issue 4, December 2025, Pages 4043-4061
Related DOI:
https://doi.org/10.1093/mnras/staf1941
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Submission history
From: Lisa Giani
[v1] Mon, 16 Feb 2026 14:56:46 UTC (2,726 KB)
https://arxiv.org/abs/2602.14804
Astrobiology, Astrochemistry,