GASPS-A Herschel Survey of Gas and Dust in Protoplanetary Disks: Summary and Initial Statistics
GASPS-A Herschel Survey of Gas and Dust in Protoplanetary Disks: Summary and Initial Statistics
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DOI：
10.1086/670826
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发表时间：
2013-05-01
影响因子：
3.5
通讯作者：
Woitke, P.
中科院分区：
文献类型：
--
作者：
Dent, W. R. F.;Thi, W. F.;Woitke, P.
我们描述了一个大规模的远红外线和连续调查的原行星盘通过年轻的碎片盘系统进行了使用ACS仪器的赫歇尔空间天文台。这一开放时间关键方案，称为GASPS（原行星系统气体巡天），目标类似于250颗年轻恒星，在窄波长区域，覆盖63 μ m处的[OI]精细结构线，这是此类物体中最亮的远红外线。一个子集的最亮的目标也调查了[OI]145 μ m，[CII]在157 μ m，以及几个过渡的H2O和高激发CO线在选定的波长在78和180 μ m之间。此外，GASPS包括连续测光在70，100和160亩，周围的灰尘排放的高峰。目标是SED II-III类金牛座T星和附近七个年轻星协的碎片盘，沿着有孤立的赫比格AeBe星的可比样本。目的是研究星周盘广泛样本中的全球气体和尘埃含量，并将结果与模型系统地结合起来。本文综述了该计划的科学目标、目标选择和观测策略。我们总结了一些初步的结果，显示线识别，列出的检测，并给出了第一个线检测的统计研究。[OI]线在63亩米是最明亮的线看到几乎所有的对象，由一个类似的10倍。总的来说，63 μ m的探测率为49%，HAeBe星的探测率为100%，金牛T星的探测率为43%。与已发表的盘状尘埃质量（主要来自亚毫米连续体，假设毫米质量不透明度的标准值）的比较表明，[OI] 63 μ m探测的尘埃质量阈值类似于10（-5）M圆点。标准化到140 pc的距离，本次调查在这条线上可以检测到84%的尘埃质量>= 10（-5）M圆点的物体;质量为10（-6）-10（-5）M圆点的物体中有32%，只能检测到极少数质量较低的异常物体。这与具有适度紫外线过量和圆盘燃烧的模型一致。对于一个给定的磁盘质量，[OI]的可探测性是较低的M星相比，较早的光谱类型。在大多数系统中，连续谱和线发射在空间和光谱上都是无法分辨的，并且集中在星星上，这表明在大多数情况下发射是来自圆盘。大约有10个物体显示出已分辨的发射，很可能来自外流。在GASPS样本中，在0.3- 400万年年龄范围内，金牛座T协会的[OI]检测率接近50%。对于每个协会在5-20百万年的年龄范围内，类似于2星仍然检测到[OI]63 μ m，没有系统中检测到年龄>20百万年的协会。与每个星协中的年轻恒星总数相比，并假设类似ISM的气体/尘埃比，这表明大约18%的恒星在1- 400万年内保持着总质量类似于1 M-木星的富含气体的盘，1-7%的恒星在5- 1000万年内保持着这样的盘，但在10- 2000万年后没有发现。在[OI]145 μ m、[CII]157 μ m和CO J = 18 - 17处也观测到了GASPS的最亮[OI]天体，探测率为20- 40%。[CII]线的检测与磁盘质量无关，这表明它更常见于紧凑的残余信封。
We describe a large-scale far-infrared line and continuum survey of protoplanetary disk through to young debris disk systems carried out using the ACS instrument on the Herschel Space Observatory. This Open Time Key program, known as GASPS (Gas Survey of Protoplanetary Systems), targeted similar to 250 young stars in narrow wavelength regions covering the [OI] fine structure line at 63 mu m the brightest far-infrared line in such objects. A subset of the brightest targets were also surveyed in [OI]145 mu m, [CII] at 157 mu m, as well as several transitions of H2O and high-excitation CO lines at selected wavelengths between 78 and 180 mu m. Additionally, GASPS included continuum photometry at 70, 100 and 160 mu m, around the peak of the dust emission. The targets were SED Class II-III T Tauri stars and debris disks from seven nearby young associations, along with a comparable sample of isolated Herbig AeBe stars. The aim was to study the global gas and dust content in a wide sample of circumstellar disks, combining the results with models in a systematic way. In this overview paper we review the scientific aims, target selection and observing strategy of the program. We summarise some of the initial results, showing line identifications, listing the detections, and giving a first statistical study of line detectability. The [OI] line at 63 mu m was the brightest line seen in almost all objects, by a factor of similar to 10. Overall [OI]63 mu m detection rates were 49%, with 100% of HAeBe stars and 43% of T Tauri stars detected. A comparison with published disk dust masses (derived mainly from sub-mm continuum, assuming standard values of the mm mass opacity) shows a dust mass threshold for [OI] 63 mu m detection of similar to 10(-5) M-circle dot. Normalising to a distance of 140 pc, 84% of objects with dust masses >= 10(-5) M-circle dot can be detected in this line in the present survey; 32% of those of mass 10(-6)-10(-5) M-circle dot, and only a very small number of unusual objects with lower masses can be detected. This is consistent with models with a moderate UV excess and disk flaring. For a given disk mass, [OI] detectability is lower for M stars compared with earlier spectral types. Both the continuum and line emission was, in most systems, spatially and spectrally unresolved and centred on the star, suggesting that emission in most cases was from the disk. Approximately 10 objects showed resolved emission, most likely from outflows. In the GASPS sample, [OI] detection rates in T Tauri associations in the 0.3-4 Myr age range were similar to 50%. For each association in the 5-20 Myr age range, similar to 2 stars remain detectable in [OI]63 mu m, and no systems were detected in associations with age >20 Myr. Comparing with the total number of young stars in each association, and assuming a ISM-like gas/dust ratio, this indicates that similar to 18% of stars retain a gas-rich disk of total mass similar to 1 M-Jupiter for 1-4 Myr, 1-7% keep such disks for 5-10 Myr, but none are detected beyond 10-20 Myr. The brightest [OI] objects from GASPS were also observed in [OI]145 mu m, [CII]157 mu m and CO J = 18 - 17, with detection rates of 20-40%. Detection of the [CII] line was not correlated with disk mass, suggesting it arises more commonly from a compact remnant envelope.