发现朝向高质量原恒星IRAS18162$-$2048的热射电复合线发射
Discovery of thermal radio recombination line emission toward the high-mass protostar IRAS18162$-$2048
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中文总结 AI 辅助
利用ALMA数据首次在高质量原恒星IRAS18162$-$2048中探测到热射电复合线H30$\alpha$，揭示其蓝移外流物质，为研究电离喷流运动学开辟新途径。
中文摘要 AI 辅助
高质量原恒星（$M_*>8~M_\odot$）最内层几十天文单位（au）内的物理条件在很大程度上仍未被探索。在这些尺度上，电离发射可能示踪光致电离气体、吸积盘的最内层区域或原恒星喷流的底部。我们以射电复合线（RRLs）的形式在高质量恒星形成区中搜寻电离发射。我们使用阿塔卡马毫米/亚毫米波阵列（ALMA）干涉仪第6波段（$\sim$1.3 mm）的档案数据，其分辨率为$\theta_\mathrm{beam}\sim53~\mathrm{mas}\times42~\mathrm{mas}$，来检查高质量原恒星IRAS18162$-$2048，即Herbig-Haro（HH）天体HH80-81的驱动源。我们首次在该原恒星中探测到RRL H30$\alpha$（静止频率=231.90093 GHz）的热发射。在我们的观测中，电离发射在空间上未被分辨，但我们估计发射区域在源距离1.4 kpc处$\lesssim50$ au。H30$\alpha$谱线轮廓宽且光谱分辨，其本地静止标准速度约为$-14~\mathrm{km~s^{-1}}$（即相对于云的系统速度蓝移约$-26~\mathrm{km~s^{-1}}$），半高全宽约为$82~\mathrm{km~s^{-1}}$。这些观测表明，H30$\alpha$谱线正在示踪该天体中众所周知的射电喷流中的蓝移外流物质。这一探测为详细研究电离喷流的运动学和物理性质开辟了可能性。
英文摘要
The physical conditions within the innermost few tens of au of high-mass protostars ($M_*>8~M_\odot$) remain largely unexplored. At these scales, ionised emission may trace photoionised gas, accretion disks, or the base of protostellar jets. We search for ionised emission in the form of radio recombination lines (RRLs) in high-mass star-forming regions. We use archival data from the Atacama Millimeter/submillimeter Array (ALMA) interferometer in band 6 ($\sim$1.3 mm) with a resolution of $θ_\mathrm{beam}\sim53~\mathrm{mas}\times42~\mathrm{mas}$ to examine the high-mass protostar IRAS18162$-$2048, driving source of the Herbig-Haro (HH) objects HH80-81. We detect, for the first time in this protostar, the thermal emission of the RRL H30$α$ ($\mathrm{rest~frequency}=231.90093$ GHz). The ionised emission is spatially unresolved in our observations, but we estimate an emitting region $\lesssim50$ au at the source distance of 1.4 kpc. The H30$α$ line profile is broad and spectrally resolved with a Local Standard of Rest velocity of $\sim-14~\mathrm{km~s^{-1}}$ (i.e., $\sim-26~\mathrm{km~s^{-1}}$ blue-shifted with respect to the systemic velocity of the cloud) and a full width at half maximum of $\sim82~\mathrm{km~s^{-1}}$. These observations suggest that the H30$α$ line is tracing outflowing blue-shifted material in the well-known radio jet from this object. This detection opens the possibility of detailed studies of the kinematics and physical properties of ionised jets.
发表机构
- Instituto de Astrofísica de Andalucía, CSIC（安达卢西亚天体物理研究所）
- National Astronomical Observatory of Japan（日本国立天文台）
- Osservatorio Astrofisico di Arcetri（阿切特里天文台）
- Universitat de Barcelona (IEEC-UB)（巴塞罗那大学）
- Institut de Radioastronomie Millimétrique（毫米波射电天文研究所）
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