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>The physical and chemical structure of Sagittarius B2 - I. Three-dimensional thermal dust and free-free continuum modeling on 100?au to 45?pc scales
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The physical and chemical structure of Sagittarius B2 - I. Three-dimensional thermal dust and free-free continuum modeling on 100?au to 45?pc scales
Context. We model the dust and free-free continuum emission in the high-mass star-forming region Sagittarius B2. Aims. We want to reconstruct the 3D density and dust temperature distribution, as a crucial input to follow-up studies of the gas velocity field and molecular abundances. Methods. We employ the 3D radiative transfer program RADMC-3D to calculate the dust temperature self-consistently, providing a given initial density distribution. This density distribution of the entire cloud complex is then recursively reconstructed, based on available continuum maps, including both single-dish and high-resolution interferometric maps that cover a wide frequency range ( ν = 40?GHz ? 4?THz). The model covers spatial scales from 45?pc down to 100?au, i.e., a spatial dynamic range of 10 ~(5) . Results. We find that the density distribution of Sagittarius B2 can be reasonably well fitted by applying a superposition of spherical cores with Plummer-like density profiles. To reproduce the spectral energy distribution, we position Sgr B2(N) along the line of sight behind the plane containing Sgr B2(M). We find that the entire cloud complex comprises a total gas mass of 8.0 × 10 ~(6) ? M _(⊙) within a diameter of 45?pc. This corresponds to an averaged gas density of 170? M _(⊙) pc ~(-3) . We estimate stellar masses of 2400? M _(⊙) and 20?700? M _(⊙) and luminosities of 1.8 × 10 ~(6) ? L _(⊙) and 1.2 × 10 ~(7) ? L _(⊙) for Sgr B2(N) and Sgr B2(M), respectively. We report H _(2) column densities of 2.9 × 10 ~(24) ?cm ~(-2) for Sgr B2(N) and 2.5 × 10 ~(24) ?cm ~(-2) for Sgr B2(M) in a 40 ′′ ?beam. For Sgr B2(S), we derive a stellar mass of 1100? M _(⊙) , a luminosity of 6.6 × 10 ~(5) ? L _(⊙) , and an H _(2) column density of 2.2 × 10 ~(24) ?cm ~(-2) in a 40 ′′ ?beam. We calculate a star formation efficiency of 5%?for Sgr B2(N) and 50%?for Sgr B2(M). This indicates that most of the gas content in Sgr B2(M) has already been converted to stars or dispersed.
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机译：上下文。我们对高质量恒星形成区射手座B2中的尘埃和自由自由连续体发射进行建模。目的我们想重建3D密度和粉尘温度分布，作为后续研究气体速度场和分子丰度的关键输入。方法。我们使用3D辐射传递程序RADMC-3D来自洽地计算粉尘温度，并提供给定的初始密度分布。然后，根据可用的连续谱图，包括覆盖宽频率范围（ν= 40？GHz？4？THz）的单碟和高分辨率干涉图，递归地重建整个云复合体的密度分布。该模型涵盖从45？pc到100？au的空间尺度，即10〜（5）的空间动态范围。结果。我们发现，通过应用球状芯与Plummer状密度分布的叠加，可以很好地拟合人马座B2的密度分布。为了重现光谱能量分布，我们沿着视线将Sgr B2（N）定位在包含Sgr B2（M）的平面后面。我们发现整个云团的总气体质量为8.0×10〜（6）？ M _（⊙）的直径在45？pc之内。这相当于平均气体密度为170?。 M _（⊙）pc〜（-3）。我们估计恒星质量为2400？ M _（⊙）和20？700？ M _（⊙）和1.8×10〜（6）的发光度？ L _（⊙）和1.2×10〜（7）？ Sgr B2（N）和Sgr B2（M）的L _（⊙）。对于Sgr B2（N），我们报告的H _（2）柱密度为2.9×10〜（24）？cm〜（-2），对于Sgr B2（M）为2.5×10〜（24）？cm〜（-2） ）放在40英尺的光束中。对于Sgr B2（S），我们得出的恒星质量为1100？ M _（⊙）的亮度为6.6×10〜（5）？ L _（⊙）和H _（2）柱密度在40''光束中为2.2×10〜（24）？cm〜（-2）。我们计算出Sgr B2（N）的恒星形成效率为5％?， Sgr B2（M）的恒星形成效率为50％?。这表明Sgr B2（M）中的大多数气体含量已转换为星状或分散了。
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