论文标题
缺少I类Protostellar磁盘
Missing water in Class I protostellar disks
论文作者
论文摘要
水是一个关键的挥发性，可为行星形成的初始阶段提供见解。从水观测到低质量原始物体所推断出的低水丰度可能表明在恒星和行星形成期间，大型尘土晶粒将水迅速锁定为冰。但是，对于新形成的行星圆盘的水蒸气丰度知之甚少。我们的目的是通过空间分辨的H $ _2^{18} $ o线的空间分辨观察结果来确定嵌入式开普勒磁盘中的水丰度，以了解恒星和行星形成期间水的演变。我们将H $ _2^{18} $ o线观测到Alma和Noema毫米干涉仪，向五个年轻的恒星对象。诺玛（Noema）观察到3 $ _ {1,3} $ - $ 2_ {2,0} $ line（e $ _ {\ rm up} $ = 203.7 k），而阿尔玛（Alma）的目标是$ 4_ {1,4} $ - $ 3_ {2,1} $ line（E $ $ _ $ _ {考虑到光学上的薄和热的发射，水柱密度是得出的。我们的观察结果对样本中五个I对象中的三个I类中的三个Kplerian磁盘发射很敏感。没有H $ _2^{18} $ O o发射对我们的五个I类磁盘中的任何一个。我们报告了集成线强度的上限。 I类磁盘中的推断水柱密度为N <10 $^{15} $ cm $^{ - 2} $在100个AU秤上，包括磁盘和信封。上限意味着相对于I类对象的H $ _2 $，$ \ Lessim 10^{ - 6} $的水丰度。考虑到磁盘的物理结构后，用$ t> $ 100 k在内部温暖磁盘上平均水丰度的上限在10 $^{ - 7} $之间，最高10 $^{ - 5} $。在I级质体周围的温暖的原恒星信封中，水蒸气并不丰富。 I类磁盘中水蒸气柱密度的上限至少比0类磁盘样结构中的值低两个级级。
Water is a key volatile that provides insights into the initial stages of planet formation. The low water abundances inferred from water observations toward low-mass protostellar objects may point to a rapid locking of water as ice by large dust grains during star and planet formation. However, little is known about the water vapor abundance in newly formed planet-forming disks. We aim to determine the water abundance in embedded Keplerian disks through spatially-resolved observations of H$_2^{18}$O lines to understand the evolution of water during star and planet formation. We present H$_2^{18}$O line observations with ALMA and NOEMA millimeter interferometers toward five young stellar objects. NOEMA observed the 3$_{1,3}$ - $2_{2,0}$ line (E$_{\rm up}$ = 203.7 K) while ALMA targeted the $4_{1,4}$ - $3_{2,1}$ line (E$_{\rm up}$ = 322.0 K). Water column densities are derived considering optically thin and thermalized emission. Our observations are sensitive to the emission from the known Keplerian disks around three out of the five Class I objects in the sample. No H$_2^{18}$O emission is detected toward any of our five Class I disks. We report upper limits to the integrated line intensities. The inferred water column densities in Class I disks are N < 10$^{15}$ cm$^{-2}$ on 100 au scales which include both disk and envelope. The upper limits imply a disk-averaged water abundance of $\lesssim 10^{-6}$ with respect to H$_2$ for Class I objects. After taking into account the physical structure of the disk, the upper limit to the water abundance averaged over the inner warm disk with $T>$ 100 K is between 10$^{-7}$ up to 10$^{-5}$. Water vapor is not abundant in warm protostellar envelopes around Class I protostars. Upper limits to the water vapor column densities in Class I disks are at least two orders magnitude lower than values found in Class 0 disk-like structures.
