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名稱Title
2018天文年會
國立金門大學
5月18日至20日

論文摘要

cis-HCOOH in the Orion KL Hot Molecular Core

[ Poster PS47 ]

Ya-Wen Yo (Department of Earth Sciences, National Taiwan Normal University); Yi-Jehng Kuan (Department of Earth Sciences, National Taiwan Normal University); Yo-Ling Chuang (Department of Earth Sciences, National Taiwan Normal University); Li-Cheng Feng (Department of Physics, National Taiwan Normal University); Guan-Ting Su (Department of Physics, National Taiwan Normal University); Chien-Hsun Li (Department of Atmospheric Sciences, National Central University)

There exist two conformers of formic acid; the trans-HCOOH has been already observed in interstellar medium. Nevertheless, the cis-HCOOH, a wobbly conformer of formic acid, was only detected in the Orion Bar photon-dominated region (PDR) recently due to its very high trans-to-cis conversion energy barrier. In addition, no cis-HCOOH was detected toward the Orion KL hot molecular core; a FUV (far-UV) photoswitching mechanism for trans-to-cis isomerization was thus proposed (Cuadrado et al. 2016). However, we have detected two cis-HCOOH lines in Orion KL unambiguously using the ALMA, with many trans-HCOOH lines also detected. The spectral emission of cis-formic acid conformers is located ~2” south of the continuum source SMA 1, and the trans- HCOOH is concentrated at SMA 1. The existence of cis-HCOOH in the optically thick Orion KL presents an immediate challenge to the FUV photoswitching scenario hence requires an alternate mechanism for trans-to-cis conversion.