An Absorption Survey Of C3h+ And C4h In Diffuse Clouds Toward Galactic Continuum Regions

Gupta, Harshal

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https://hdl.handle.net/2142/116687 Copy

Description

Title

An Absorption Survey Of C3h+ And C4h In Diffuse Clouds Toward Galactic Continuum Regions

Author(s)

Gupta, Harshal

Contributor(s)

• McCarthy, Michael C.
• Gerin, Maryvonne
• Lee, Kelvin

Issue Date

2022-06-20

Keyword(s)

Astronomy

Abstract

Observations of the diffuse interstellar gas over the past few decades have revealed a surprisingly rich molecular inventory comprising over 25\% of all known interstellar molecules. While the molecules observed in diffuse clouds are small relative to ones found in dark clouds, considerable progress has been made in recent years towards detecting larger, more complex molecules.\footnote{Liszt, H.~S., Gerin, M., Beasley, A., \& Pety, J., 2018, Astrophysical Journal, 856, 151; {\em and references therein.}}$^{,}$\footnote{Gerin, M., Liszt, H., Neufeld, D., et al. 2019, Astronomy \& Astrophysics, 622, A26; {\em and references therein.}} There is also clear evidence at optical wavelengths for a very large molecule---the fullerene ion \chem{C_{60}^+}---in the diffuse gas.\footnote{Maier, J.~P. \& Campbell, E.~K. 2016, Phil. Trans. R. Soc. A, 374, (issue 2076), 1} Using the 100-m Green Bank Telescope, we undertook observations of 8 sightlines toward bright centimeter continuum regions in the Galaxy, and detected the \chem{C_{3}H^{+}} ion and the \chem{C_{4}H} radical in absorption from foreground diffuse clouds along 7 sightlines.\footnote{Our sample includes two sightlines where millimeter-wave absorption from \chem{C_{3}H^{+}} has previously been detected.$^{b}$} Both molecules are thought to be key intermediates in the carbon chemistry of the interstellar medium, and to our knowledge \chem{C_{3}H^{+}} is currently the largest carbon chain ion and \chem{C_{4}H} the largest carbon chain radical detected by radio astronomy in the diffuse gas. I will discuss our results within the context of understanding hydrocarbon chemistry, establishing the limits of molecular complexity, and bridging the gap between small molecules and very large molecules in the diffuse gas. I will also discuss the prospects of enlarging the molecular inventory of diffuse clouds, particularly large polyatomic ions and radicals,\footnote{Molecular ions such as \chem{C_{3}H^{+}} are far more challenging to produce in the laboratory than carbon chain radicals, and might first be found in space.} by means of absorption surveys exploiting long pathlengths toward bright continuum sources.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116687

DOI

https://doi.org/10.15278/isms.2022.MN11

Copyright and License Information

Copyright 2022 held by the authors

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