Chemical models predict that in cold cores gas-phase methanol is expected to be abundant at the outer edge of the CO depletion zone, where CO is actively adsorbed. CO adsorption correlates with volume density in cold cores, and, in nearby molecular clouds, the catastrophic CO freeze-out happens at volume densities above 10$^4$ cm$^{-3}$. The methanol production rate is maximized there and its freeze-out rate does not overcome its production rate, while the molecules are shielded from UV destruction by gas and dust. Thus, in cold cores, methanol abundance should generally correlate with visual extinction that depends both on volume and column density. In this work, we test the most basic model prediction that maximum methanol abundance is associated with a local $A_V\simeq$4 mag in dense cores and constrain the model parameters with the observational data. With the IRAM 30 m antenna, we mapped the CH$_3$OH (2-1) and (3-2) transitions toward seven dense cores in the L1495 filament in Taurus to measure the methanol abundance. We use the Herschel/SPIRE maps to estimate visual extinction, and the C$^{18}$O(2-1) maps from Tafalla & Hacar (2015) to estimate CO depletion. We explored the observed and modeled correlations between the methanol abundances, CO depletion, and visual extinction varying the key model parameters. The modeling results show that hydrogen surface diffusion via tunneling is crucial to reproduce the observed methanol abundances, and the needed reactive desorption efficiency matches the one deduced from laboratory experiments.
ALMA Observations of Cold Methanol Gas in the Large Magellanic Cloud (LMC): N79 South GMC
S. N. Bose National Centre for Basic Sciences（S.N. 玻色基础科学国家中心）；Institute of Science and Technology, Niigata University（新潟大学科学技术研究院）；Rosseland Centre for Solar Physics, University of Oslo（奥斯陆大学罗斯兰太阳物理中心）；Institute of Theoretical Astrophysics, University of Oslo（奥斯陆大学理论天体物理研究所）；Institute of Science Tokyo（东京科学大学）；RIKEN Pioneering Research Institute（理化学研究所先导研究本部）；Institute of Astronomy Space and Earth Science（天文宇宙地球科学研究院）
Ubiquity of Methanol and its related Chemical Segregation in Orion Starless Cores: the ALMASOP Sample
Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天文物理研究所）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences（日本国立自然科学研究所国家天文台野边山射电天文台）；The Graduate University for Advanced Studies, SOKENDAI（综合研究大学院大学）；Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究院）；University of Science and Technology, Korea (UST)（韩国科学技术院）；School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（教育部现代天文与天体物理重点实验室（南京大学））；Physical Research laboratory（物理研究实验室）
Testing various assumptions for radiolysis, non-diffusive chemistry, and chemical desorption in cold cores
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS（波尔多天体物理学实验室，波尔多大学，法国国家科学研究中心）；School of Astronomy & Space Science, Nanjing University（南京大学天文与空间科学学院）
Semi-analytic Inference of Satellite Densities in the Cold Dark Matter Model Part I. Comparison to Ultra-faint Dwarf Kinematics
Leinweber Institute for Theoretical Physics, University of California, Berkeley（加州大学伯克利分校莱因韦伯理论物理研究所）；Theoretical Physics Group, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室理论物理组）；Department of Physics, Princeton University（普林斯顿大学物理系）；Department of Physics and Astronomy, University of California - Irvine（加州大学尔湾分校物理与天文学系）；Center for Computational Astrophysics, Flatiron Institute（平顿研究所计算天体物理学中心）
