ASTRONOMICAL DETECTION OF THE INTERSTELLAR ANION C10H− TOWARDS TMC-1 FROM THE GOTHAM LARGE PROGRAM ON THE GBT

Remijan, Anthony

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Title

ASTRONOMICAL DETECTION OF THE INTERSTELLAR ANION C10H− TOWARDS TMC-1 FROM THE GOTHAM LARGE PROGRAM ON THE GBT

Author(s)

Remijan, Anthony

Issue Date

2023-06-22

Keyword(s)

Astronomy

Abstract

Using data from the GOTHAM (GBT Observations of TMC-1: Hunting for Aromatic Molecules) survey, we report the first astronomical detection of the C₁₀H− anion. The astronomical observations also provided the necessary data to refine the spectroscopic parameters of C₁₀H−. From the velocity stacked data and the matched filter response, C₁₀H− is detected at >9σ confidence level at a column density of 4.04⁺¹⁰.⁶⁷-₂.₂₃ × 10¹¹ cm−². A dedicated search for the C₁₀H radical was also conducted towards TMC-1. In this case, the stacked molecular emission of C₁₀H was detected at a ∼3.2σ confidence interval at a column density of 2.02⁺².⁶⁸-₀.₈₂ × 10¹¹ cm−². However, since the determined confidence level is currently <5σ, we consider the identification of C₁₀H as tentative. The full GOTHAM dataset was also used to better characterize the physical parameters including column density, excitation temperature, linewidth, and source size for the C₄H, C₆H and C₈H radicals and their respective anions, and the measured column densities were compared to the predictions from a gas/grain chemical formation model and from a machine learning analysis. Given the measured values, the C₁₀H−/C₁₀H column density ratio is ∼2.0⁺⁵.⁹-₁.₆ - the highest value measured between an anion and neutral species to date. Such a high ratio is at odds with current theories for interstellar anion chemistry. For the radical species, both models can reproduce the measured abundances found from the survey; however, the machine learning analysis matches the detected anion abundances much better than the gas/grain chemical model, suggesting that the current understanding of the formation chemistry of molecular anions is still highly uncertain.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122400

DOI

https://doi.org/10.15278/isms.2023.6959

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