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

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 $3.4$-$4.0\mu$m spectrum, aided by NASA/IRTF $L^{\prime }$ imaging and $2$-$4\mu$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 $3.535\mu$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 $15.4\mu$m shoulder absorption observed toward GC MYSOs arises from CO${}_2$ ice mixed with CH${}_3$OH.

Accepted for publication in the Astrophysical Journal Letters

References in corpus (8)

• The UKIDSS Galactic Plane Survey
• The largest oxigen bearing organic molecule repository
• Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
• Point Sources from a Spitzer IRAC Survey of the Galactic Center
• Interstellar Extinction and Long-Period Variables in the Galactic Center
• A study of methanol and silicon monoxide production through episodic explosions of grain mantles in the Central Molecular Zone
• Gas absorption and dust extinction towards the Orion Nebula Cluster
• Do individual Spitzer young stellar object candidates enclose multiple UKIDSS sources?

Cited by in corpus (5)

• Widespread Presence of Glycolaldehyde and Ethylene Glycol Around Sagittarius B2
• Comparative Electron Irradiations of Amorphous and Crystalline Astrophysical Ice Analogues
• Sagittarius B1 -- A Patchwork of H II Regions and PhotoDissociation Regions
• Massive Young Stellar Objects in the Galactic Center. II. Seeing Through the Ice-rich Envelopes
• Discovery of two infrared objects with strong ice absorption in the AKARI slit-less spectroscopic survey of the Galactic Plane