标题： 詹姆斯·韦布空间望远镜对自由漂浮的行星质量天体及其盘的光谱学研究 显示英文标题

标题： Spectroscopy of Free-Floating Planetary-Mass Objects and their disks with JWST

摘要： 已知自由漂浮的行星质量天体（FFPMOs）在年轻年龄时拥有盘。在此，我们展示了八个年轻FFPMOs的1-13$\mu m$光谱，这些天体的质量为5-10 M$_\mathrm{Jup}$ （年龄为1-5 Myr），使用詹姆斯·韦布空间望远镜上的NIRSpec和MIRI仪器。我们推导了这些目标的基本特性，并发现光谱类型为M9.5到L4，有效温度为1600-1900 K。我们目标的光球光谱在相似温度下显示出明显的多样性，特别是在3-5$\mu m$范围内，这无法用现有的大气模型解释。我们在其中一个目标的光球中发现了硅酸盐吸收特征，这是非常年轻的FFPMOs中的首次检测，表明它们的冷大气中有硅酸盐云。我们的六个物体在光球之上显示出中红外过量辐射，以及硅酸盐发射特征，证明了盘的存在。后者的特征形状和强度构成了颗粒增长和结晶的有力证据，类似于在更高质量的棕矮星和恒星中所见的情况。我们还在几个目标的盘中检测到了碳氢化合物分子的发射线。这些是迄今为止发现的质量最低的孤立天体，其盘中出现了硅酸盐和碳氢化合物的发射特征。盘的存在及其特征表明，在自由漂浮的行星质量天体周围有可能形成岩石伴星。 显示英文摘要

摘要： Free-floating planetary-mass objects (FFPMOs) are known to harbor disks at young ages. Here, we present 1-13 $\mu m$ spectra for eight young FFPMOs with masses of 5-10 M$_\mathrm{Jup}$ (at ages of 1-5 Myr), using the NIRSpec and MIRI instruments on the James Webb Space Telescope. We derive fundamental properties of these targets, and find spectral types of M9.5 to L4, with effective temperatures of 1600-1900 K. The photospheric spectra of our targets show a clear diversity at similar temperatures, especially in the 3-5 $\mu m$ range, unaccounted for by existing atmospheric models. We find a silicate absorption feature in the photosphere of one of our targets, the first such detection in very young FFPMOs, indicating silicate clouds in their cool atmospheres. Six of our objects show mid-infrared excess emission above the photosphere, as well as silicate emission features, demonstrating the presence of disks. The shape and strength of the latter features constitute strong evidence of grain growth and crystallization, similar to what is seen in more massive brown dwarfs and stars. We also detect emission lines from hydrocarbon molecules in the disks of several targets. These are the lowest mass isolated objects found so far with silicate and hydrocarbon emission features arising in their disks. The presence of disks and their characteristics point to the potential for the formation of rocky companions around free-floating planetary-mass objects.