Detectability of giant planets in protoplanetary disks by CO emission lines
Detectability of giant planets in protoplanetary disks by CO emission lines
复制标题
通过二氧化碳排放线可探测到原行星盘中的巨行星
DOI：
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发表时间：
2010
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通讯作者：
R. Boekel
中科院分区：
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作者：
Z. Regály;Z. Sándor;C. Dullemond;R. Boekel
本文拟通过研究金牛座T星周围原行星盘的近红外发射光谱，提供一种间接探测类木行星的方法。我们的想法是研究一颗大质量的行星是否会对圆盘大气中出现的光谱线产生任何可观察到的影响。作为一种示踪分子，我们提出了CO，它在盘状大气的反振动基本带中被激发到~2-3天文单位（取决于恒星质量）的距离，这被认为是类地行星形成的地方。合成分子的谱线轮廓用自己开发的半解析双层圆盘模型计算。将二维气体动力学纳入合成谱线的计算中。我们证明了嵌入在原行星盘中的大质量行星强烈地影响了最初圆形的开普勒气体动力学。通过比较有行星和无行星盘模型的CO谱线，可以探测到气体的扰动运动。行星信号有两个主要特征：永久的线轮廓不对称，以及与巨行星轨道相位相关的短时间尺度变化。我们发现，不对称的强度取决于恒星-行星-盘系统的物理参数，如盘的倾角、行星和恒星的质量、轨道距离和盘内腔的大小。永久的线轮廓不对称是由巨行星打开的间隙中处于偏心状态的圆盘引起的。然而，变分量是由绕轨道运行的巨行星引起的局部动力扰动的结果。我们展示了一颗正在形成的巨行星，仍然镶嵌在原行星盘中，可以使用当代或未来的高分辨率近红外光谱仪（如VLT/CRIRES和ELT/METIS）进行探测。
In this paper we intend to provide an indirect method to detect Jovian planets by studying near infrared emission spectra originating in the protoplanetary disks around T Tauri stars. Our idea is to investigate whether a massive planet could induce any observable effect on the spectral lines emerging in the disks atmosphere. As a tracer molecule we propose CO, which is excited in the ro-vibrational fundamental band in the disk atmosphere to a distance of ~2-3 AU (depending on the stellar mass) where terrestrial planets are thought to form. The synthetic molecular spectral line profiles were calculated by an own developed semi-analytical double layer disk model. 2D gas dynamics were incorporated in the calculation of synthetic spectral lines. We demonstrate that a massive planet embedded in a protoplanetary disk strongly influences the originally circular Keplerian gas dynamics. The perturbed motion of the gas can be detected by comparing the CO line profiles in emission, which is emerge from planet-bearing to those of planet-free disk models. The planet signal has two major characteristics: a permanent line profile asymmetry, and short timescale variability correlated with the orbital phase of the giant planet. We have found that the strength of the asymmetry depends on the physical parameters of the star-planet-disk system, such as the disk inclination angle, the planetary and stellar masses, the orbital distance, and the size of the disk inner cavity. The permanent line profile asymmetry is caused by a disk in an eccentric state in the gap opened by the giant planet. However, the variable component is a consequence of the local dynamical perturbation by the orbiting giant planet. We show that a forming giant planet, still embedded in the protoplanetary disk, can be detected using contemporary or future high-resolution near-IR spectrographs like VLT/CRIRES and ELT/METIS.