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外文期刊>The Astrophysical journal
>THE SNOW LINE IN VISCOUS DISKS AROUND LOW-MASS STARS: IMPLICATIONS FOR WATER DELIVERY TO TERRESTRIAL PLANETS IN THE HABITABLE ZONE
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THE SNOW LINE IN VISCOUS DISKS AROUND LOW-MASS STARS: IMPLICATIONS FOR WATER DELIVERY TO TERRESTRIAL PLANETS IN THE HABITABLE ZONE
The water-ice or snow line is one of the key properties of protoplanetary disks that determines the water content of terrestrial planets in the habitable zone. Its location is determined by the properties of the star, the mass accretion rate through the disk, and the size distribution of dust suspended in the disk. We calculate the snow-line location from recent observations of mass accretion rates and as a function of stellar mass. By taking the observed dispersion in mass accretion rates as a measure of the dispersion in initial disk mass, we find that stars of a given mass will exhibit a range of snow-line locations. At a given age and stellar mass, the observed dispersion in mass accretion rates of 0.4 dex naturally leads to a dispersion in snow-line locations of ~0.2 dex. For ISM-like dust sizes, the 1σ snow-line location among solar-mass stars of the same age ranges from ~2 to ~5 AU. For more realistic dust opacities that include larger grains, the snow line is located up to two times closer to the star. We use these locations and the outcome of N-body simulations to predict the amount of water delivered to terrestrial planets that formed in situ in the habitable zone. We find that the dispersion in snow-line locations leads to a large range in water content. For ISM-like dust sizes, a significant fraction of habitable-zone terrestrial planets around Sun-like stars remain dry, and no water is delivered to the habitable zones of low-mass M stars () as in previous works. The closer-in snow line in disks with larger grains enables water delivery to the habitable zone for a significant fraction of M stars and all FGK stars. Considering their larger numbers and higher planet occurrence, M stars may host most of the water-rich terrestrial planets in the galaxy if these planets are able to hold on to their water in their subsequent evolution.
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机译：水冰或雪线是原行星盘的关键特性之一，它决定了宜居地带中行星的水分含量。它的位置取决于恒星的属性，穿过圆盘的质量增加率以及悬浮在圆盘中的灰尘的尺寸分布。我们根据最近的质量积聚率和恒星质量的函数来计算雪线位置。通过将观察到的质量增长速率的离散度作为初始圆盘质量的离散度的度量，我们发现给定质量的恒星将表现出一系列的雪线位置。在给定的年龄和恒星质量下，观察到的质量增加速率的分散为0.4 dex，自然导致在雪线位置的分散为〜0.2 dex。对于类似ISM的尘埃大小，相同年龄的太阳质量恒星中1σ雪线的位置范围为〜2 AU ~~ 5 AU。为了获得更大颗粒的更真实的灰尘不透明效果，雪线的位置距离恒星最近两倍。我们使用这些位置和N体模拟的结果来预测输送到在可居住区域内就地形成的地球行星的水量。我们发现，雪线位置的分散会导致大范围的水含量。对于类似ISM的尘埃大小，像太阳一样的恒星周围的可居住区陆地行星中有很大一部分保持干燥，并且没有像以前的工作那样将水输送到低质量M恒星的可居住区（）。具有较大颗粒的圆盘中靠近雪线的水可以将水输送到大部分M星和所有FGK星的宜居区域。考虑到它们的数量更大和发生的行星更高，如果M星能够在随后的演化中保持其水力，那么它们可能是银河系中大多数富含水的陆地行星的宿主。
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