PDS 70盘的不对称尘埃积累由ALMA Band 3观测揭示
Asymmetric dust accumulation of the PDS 70 disk revealed by ALMA Band 3 observations
AI总结：
本研究利用ALMA Band 3高分辨率观测揭示了PDS 70盘西北方向显著的不对称尘埃积累，结合数值模拟限制了外环偏心率及行星PDS 70c的质量上限，并探讨了盘结构形成与行星演化机制。
AI中文摘要：
PDS 70系统在其盘内拥有两颗行星，是检验行星对尘埃积累、生长及持续行星形成影响的理想目标。在此，我们展示了ALMA Band 3（3.0 mm）对PDS 70盘的高分辨率（0.''07 = 8 au）尘埃连续谱观测结果。先前的Band 7观测显示尘埃环带有轻微不对称性，而我们的Band 3观测在西北方向揭示了一个更显著的不对称峰值，其强度比其他方向高2.5倍，且光谱指数处于局部最低值（α_SED ~ 2.2）。这表明在峰值处沿径向和方位角均积累了大量尘埃。我们还在Band 3图像中探测到恒星位置附近的点源辐射，可能为自由-自由辐射。基于中心恒星与外环的位置，我们限制外环的偏心率e<0.04。通过与数值模拟对比，在气体湍流强度α_turb = 10^-3的假设下，我们限制PDS 70c的质量小于4.9木星质量。随后，我们讨论了盘结构的形成机制及盘内进一步的行星形成情景。
英文摘要：
The PDS 70 system, hosting two planets within its disk, is an ideal target for examining the effect of planets on dust accumulation, growth, and ongoing planet formation. Here, we present high-resolution ($0.''07 = 8 \ \mathrm{au}$) dust continuum observations of the PDS 70 disk in ALMA Band 3 (3.0 mm). While previous Band 7 observations showed a dust ring with slight asymmetry, our Band 3 observations reveal a more prominent asymmetric peak in the northwest direction, where the intensity is 2.5 times higher than in other directions and the spectral index is at the local minimum with $α_{\mathrm{SED}} \sim 2.2$. This indicates that a substantial amount of dust is accumulated both radially and azimuthally in the peak. We also detect point-source emission around the stellar position in the Band 3 image, which is likely to be free-free emission. We constrain the eccentricity of the outer ring to be $e<0.04$ from the position of the central star and the outer ring. From the comparison with numerical simulations, we constrain the mass of PDS 70c to be less than 4.9 Jupiter masses if the gas turbulence strength $α_{\mathrm{turb}} = 10^{-3}$. Then, we discuss the formation mechanism of the disk structures and further planet formation scenarios in the disk.
