open access publication

Article, 2024

Rotational Spectrum and First Interstellar Detection of 2-methoxyethanol Using ALMA Observations of NGC 6334I

The Astrophysical Journal Letters, ISSN 2041-8205, 2041-8213, Volume 965, 2, Page l23, 10.3847/2041-8213/ad37ff

Contributors

Fried, Zachary T P 0000-0001-5020-5774 [1] El-Abd, Samer J [2] [3] Hays, Brian M [4] Wenzel, Gabi [1] Byrne, Alex N 0000-0002-4593-518X [1] Margulès, Laurent D [4] Motiyenko, Roman A 0000-0002-3849-1533 [4] Shipman, Steven T [5] Horne, Maria P [6] Jørgensen, Jes Kristian 0000-0001-9133-8047 [7] Brogan, Crystal L 0000-0002-6558-7653 [3] Hunter, Todd R 0000-0001-6492-0090 [3] Remijan, Anthony J [3] Lipnicky, Andrew 0000-0002-6667-7773 [3] Loomis, Ryan A 0000-0002-8932-1219 [3] Mcguire, Brett A 0000-0003-1254-4817 [1] [3]

Affiliations

  1. [1] Massachusetts Institute of Technology
    2. [NORA names: United States; America, North; OECD];
  2. [2] University of Virginia
    3. [NORA names: United States; America, North; OECD];
  3. [3] National Radio Astronomy Observatory
    4. [NORA names: United States; America, North; OECD];
  4. [4] University of Lille
    5. [NORA names: France; Europe, EU; OECD];
  5. [5] BrightSpec
    6. [NORA names: United States; America, North; OECD];

Abstract

We use both chirped-pulse Fourier transform and frequency-modulated absorption spectroscopy to study the rotational spectrum of 2-methoxyethanol (CH3OCH2CH2OH) in several frequency regions ranging from 8.7 to 500 GHz. The resulting rotational parameters permitted a search for this molecule in Atacama Large Millimeter/submillimeter Array (ALMA) observations toward the massive protocluster NGC 6334I, as well as source B of the low-mass protostellar system IRAS 16293−2422. A total of 25 rotational transitions are observed in the ALMA Band 4 data toward NGC 6334I, resulting in the first interstellar detection of 2-methoxyethanol. A column density of 1.3−0.9+1.4×1017 cm−2 is derived at an excitation temperature of 143−39+31 K. However, molecular signal is not observed in the Band 7 data toward IRAS 16293−2422B, and an upper-limit column density of 2.5 × 1015 cm−2 is determined. Various possible formation pathways—including radical recombination and insertion reactions—are discussed. We also investigate physical differences between the two interstellar sources that could result in the observed abundance variations.

Keywords

Atacama, Atacama Large Millimeter/submillimeter Array, Atacama Large Millimeter/submillimeter Array observations, CH3OCH2CH2OH, First, Fourier transform, IRAS, Millimeter/submillimeter Array, NGC, NGC 6334I, absorption spectroscopy, abundance, abundance variations, array, band, band 4 data, band 7 data, cm-2, column, column density, density, differences, excitation, excitation temperature, formation, frequency, frequency region, frequency-modulation absorption spectroscopy, insertion, interstellar sources, molecular signals, molecules, observations, parameters, physical differences, radical recombination, recombination, region, rotation, rotation parameters, rotational spectrum, rotational transitions, search, signal, source, spectra, spectroscopy, temperature, transformation, transition, variation

Funders

  • Directorate for Mathematical & Physical Sciences
  • Arnold and Mabel Beckman Foundation
  • Agence Nationale de la Recherche

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