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arXiv 1811.04553astro-ph.GAastro-ph.IM
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用卷积神经网络约束冲压压力剥离下星系的三维轨道

Constraining the three-dimensional orbits of galaxies under ram pressure stripping with convolutional neural networks

Kenji Bekki

摘要:

盘状星系气体的冲压压力剥离(RPS)一直被认为在星系团和星系团的演化中起着至关重要的作用。对于给定的团内介质密度和盘星系的速度,RPS可以由两个角度(θ和φ)控制,这两个角度定义了星系在主星系团内的三维运动方向矢量和星系的自旋矢量之间的角度关系。在这里,我们提出了一种新的方法,其中卷积神经网络(CNN)被用来限制在RPS下的盘星系的theta和phi。我们首先通过使用~10^5幅来自具有不同θ和φ的众多RPS模型的星系气体分布的合成图像来训练CNN。然后,我们将训练好的CNN应用于新的测试RPS模型,以预测theta和phi。正确的和预测的θ和$ϕ$之间的相似性通过余弦相似性(cos-Theta)来测量,其中cos-Theta =1是完全准确的预测。我们发现,测试模型之间的平均cos-Theta为~0.95,这意味着通过将CNN应用于其气体的空间分布,可以很好地约束theta和phi。这一结果表明,如果ICM处于流体静力平衡状态(因此不运动),则盘星系在其宿主星系团内的3D轨道可以受到RPS剥离的气体空间分布的限制。我们讨论了该方法的应用,HI调查,如WALLABY和SKA项目。

英文摘要:

Ram pressure stripping (RPS) of gas from disk galaxies has long been considered to play vital roles in galaxy evolution within groups and clusters. For a given density of intracluster medium (ICM) and a given velocity of a disk galaxy, RPS can be controlled by two angles (theta and phi) that define the angular relationship between the direction vector of the galaxy's three-dimensional (3D) motion within its host cluster and the galaxy's spin vector. We here propose a new method in which convolutional neutral networks (CNNs) are used to constrain theta and phi of disk galaxies under RPS. We first train a CNN by using ~10^5 synthesized images of gaseous distributions of the galaxies from numerous RPS models with different theta and phi. We then apply the trained CNN to a new test RPS model to predict theta and phi. The similarity between the correct and predicted theta and $ϕ$ is measured by cosine similarity (cos-Theta) with cos-Theta =1 being perfectly accurate prediction. We show that the average cos-Theta among test models is ~0.95, which means that theta and phi can be constrained well by applying the CNN to the spatial distributions of their gas. This result suggests that if the ICM is in hydrostatic equilibrium (thus not moving), the 3D orbit of a disk galaxy within its host cluster can be constrained by the spatial distribution of the gas being stripped by RPS. We discuss the applications of the method to HI surveys such as WALLABY and SKA projects.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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