Abundant Methanol Ice toward a Massive Young Stellar Object in the Central Molecular Zone

Deokkeun An; Kris Sellgren; A. C. Adwin Boogert; Solange V. Ramírez; Tae-Soo Pyo

doi:10.3847/2041-8213/aa7cfe

paper

Abundant Methanol Ice toward a Massive Young Stellar Object in the Central Molecular Zone

arXiv:1707.03120 · doi:10.3847/2041-8213/aa7cfe

Abstract

Previous radio observations revealed widespread gas-phase methanol (CH $_{3}$ OH) in the Central Molecular Zone (CMZ) at the Galactic center (GC), but its origin remains unclear. Here, we report the discovery of CH $_{3}$ OH ice toward a star in the CMZ, based on a Subaru $3.4$ - $4.0 μ$ m spectrum, aided by NASA/IRTF $L^{'}$ imaging and $2$ - $4 μ$ m spectra. The star lies $\sim 8000$ au away in projection from a massive young stellar object (MYSO). Its observed high CH $_{3}$ OH ice abundance ( $17% \pm 3%$ relative to H $_{2}$ O ice) suggests that the $3.535 μ$ m CH $_{3}$ OH ice absorption likely arises in the MYSO's extended envelope. However, it is also possible that CH $_{3}$ OH ice forms with a higher abundance in dense clouds within the CMZ, compared to within the disk. Either way, our result implies that gas-phase CH $_{3}$ OH in the CMZ can be largely produced by desorption from icy grains. The high solid CH $_{3}$ OH abundance confirms the prominent $15.4 μ$ m shoulder absorption observed toward GC MYSOs arises from CO $_{2}$ ice mixed with CH $_{3}$ OH.

arXiv commentAccepted for publication in the Astrophysical Journal Letters

Abundant Methanol Ice toward a Massive Young Stellar Object in the Central Molecular Zone

Abstract

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