Article,
Rotational Spectrum and First Interstellar Detection of 2-methoxyethanol Using ALMA Observations of NGC 6334I
Affiliations
- [1] Massachusetts Institute of Technology [NORA names: United States; America, North; OECD];
- [2] University of Virginia [NORA names: United States; America, North; OECD];
- [3] National Radio Astronomy Observatory [NORA names: United States; America, North; OECD];
- [4] Laboratoire de Physique des Lasers [NORA names: France; Europe, EU; OECD];
- [5] New College of Florida [NORA names: United States; America, North; OECD];
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Abstract
We use both chirped-pulse Fourier transform and frequency-modulated absorption spectroscopy to study the rotational spectrum of 2-methoxyethanol (CHOCHCHOH) 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 × 10 17 cm 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 × 10 cm 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.