Gravitationally Unstable Condensations Revealed by ALMA in the TUKH122 Prestellar Core in the Orion A Cloud
Gravitationally Unstable Condensations Revealed by ALMA in the TUKH122 Prestellar Core in the Orion A Cloud
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DOI：
10.3847/1538-4357/aab3d0
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发表时间：
2018-03
期刊：
影响因子：
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通讯作者：
S. Ohashi;P. Sanhueza;N. Sakai;R. Kandori;Minho Choi;T. Hirota;Q. Nguyễn-Lu’o’ng;K. Tatematsu
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作者：
S. Ohashi;P. Sanhueza;N. Sakai;R. Kandori;Minho Choi;T. Hirota;Q. Nguyễn-Lu’o’ng;K. Tatematsu
我们利用ALMA 3 mm尘埃连续体、N2H+ (J = 1−0)和CH3OH（）分子线观测了猎户座A星云中的TUKH122恒星前核心。先前的研究表明，TUKH122很可能处于恒星形成的边缘，因为湍流几乎已经消散，并且在猎户座A星云的其他无恒星核心中发生了化学演变。结合ALMA 12 m和ACA数据，我们恢复了分辨率为~ 5″（对应0.01 pc）的扩展发射，并确定了6个质量范围为0.1-0.4 m⊙、半径为0.01 pc的凝聚。根据维里分析，这些凝聚物被重力束缚，并嵌入在细丝中，包括质量为~ 29 M⊙的细长核心和赫歇尔导出的径向密度曲线r−1.6。这些缩聚物的分离为~ 0.035 pc，与密度为4.4 × 105 cm−3时的热Jeans长度一致。这种密度与地核的中心部分相似。我们还发现N2H+分子在尘埃峰凝结时有耗竭的趋势。由于线宽变宽，这种凝结可能开始坍塌。因此，由于热Jeans不稳定性，碎片仍然发生在恒星前核心，并且在TUKH122恒星前核心内形成了多颗恒星。CH3OH辐射呈大的壳状分布，并围绕在这些凝聚物周围，表明尘埃颗粒上形成的CH3OH分子通过非热解吸（如宇宙射线诱导的紫外线辐射引起的光蒸发）释放到气相中。
We have investigated the TUKH122 prestellar core in the Orion A cloud using ALMA 3 mm dust continuum, N2H+ (J = 1−0), and CH3OH ( ) molecular-line observations. Previous studies showed that TUKH122 is likely on the verge of star formation because the turbulence is almost dissipated and chemically evolved among other starless cores in the Orion A cloud. By combining ALMA 12 m and ACA data, we recover extended emission with a resolution of ∼5″ corresponding to 0.01 pc and identify six condensations with a mass range of 0.1–0.4 M⊙ and a radius of ≲0.01 pc. These condensations are gravitationally bound following a virial analysis and are embedded in the filament, including the elongated core with a mass of ∼29 M⊙ and a radial density profile of r−1.6 derived by Herschel. The separation of these condensations is ∼0.035 pc, consistent with the thermal Jeans length at a density of 4.4 × 105 cm−3. This density is similar to the central part of the core. We also find a tendency for the N2H+ molecule to deplete at the dust peak condensation. This condensation may be beginning to collapse because the line width becomes broader. Therefore, the fragmentation still occurs in the prestellar core by thermal Jeans instability, and multiple stars are formed within the TUKH122 prestellar core. The CH3OH emission shows a large shell-like distribution and surrounds these condensations, suggesting that the CH3OH molecule formed on dust grains is released into the gas phase by nonthermal desorption such as photoevaporation caused by cosmic-ray-induced UV radiation.