We present new Atacama Large Millimeter/submillimeter Array (ALMA) continuum and NH₂D, N₂D⁺, and H₂D⁺ line emission at matched, ∼100 au resolution toward the dense star-forming cores SM1N and N6 within the Ophiuchus molecular cloud. We determine the density and temperature structure of SM1N based on radiative transfer modeling and simulated observations of the multiwavelength continuum emission at 0.8, 2, and 3 mm. We show that SM1N is best fit by either a broken power-law or Plummer-like density profile with high central densities (n ∼ 10⁸ cm⁻³), and an inner transition radius of only ∼80–300 au. The free-fall time of the inner region is only a few ×10³ yr. The continuum modeling rules out the presence of an embedded first hydrostatic core (FHSC) or protostar. SM1N is therefore a dynamically unstable but still starless core. We find that NH₂D is likely depleted at high densities within SM1N. The nonthermal velocity dispersions increase from NH₂D to N₂H⁺ and H₂D⁺, possibly tracing increasing (but still subsonic) infall speeds at higher densities as predicted by some models of starless core contraction. Toward N6, we confirm the previous ALMA detection of a faint, embedded point source (N6-mm) in 0.8 mm continuum emission. NH₂D and N₂D⁺ avoid N6-mm within ∼100 au, while H₂D⁺ is not strongly detected toward N6. The distribution of these tracers is consistent with heating by a young, warm object. N6-mm thus remains one of the best candidate FHSCs detected so far, although its observed (sub)millimeter luminosity remains below predictions for FHSCs.

中文翻译：

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簇状核心塌陷的初始条件：100 au 分辨率下 Oph A SM1N 和 N6 的多波长分析

我们展示了新的阿塔卡马大型毫米/亚毫米阵列 (ALMA) 连续谱和 NH ₂ D、N ₂ D ⁺和 H ₂ D ⁺线发射，以匹配的约 100 au 分辨率向蛇夫座内的致密恒星形成核心 SM1N 和 N6 发射分子云。我们根据辐射传输模型和 0.8、2 和 3 mm 多波长连续发射的模拟观测确定了 SM1N 的密度和温度结构。我们证明 SM1N 最适合破碎的幂律或具有高中心密度的类 Plummer 密度分布（n∼ 10 ⁸ cm ^-3 )，内部过渡半径仅为∼80–300 au。内部区域的自由落体时间只有几×10 ³年。连续介质模型排除了嵌入式第一静水力核心（FHSC）或原恒星的存在。因此，SM1N 是一个动态不稳定但仍然无星的核心。我们发现 NH ₂ D 在 SM1N 内的高密度下可能会被耗尽。非热速度色散从 NH ₂ D 增加到 N ₂ H ⁺和 H ₂ D ⁺，可能会追踪一些无星核心收缩模型所预测的更高密度下的增加（但仍然是亚音速）的坠落速度。对于 N6，我们确认了之前 ALMA 在 0.8 mm 连续发射中检测到的微弱嵌入式点源 (N6-mm)。 NH ₂ D 和N ₂ D ⁺在∼100 au 范围内避开N6-mm，而H ₂ D ⁺对N6 没有强烈检测到。这些示踪剂的分布与年轻温暖物体的加热一致。因此，N6-mm 仍然是迄今为止检测到的最佳候选 FHSC 之一，尽管其观测到的（亚）毫米光度仍然低于 FHSC 的预测。