我们从训练和评估卷积神经网络（CNN）来预测星系形状，从暗能量调查（DES DR 1）的第一次数据发布的宽视场调查图像中得到我们的结果。我们使用传统的形状测量作为地面实况，从重叠，更深的调查，较少的天空覆盖，加拿大-法国夏威夷望远镜透镜调查（CFHTLenS）。我们证明，CNN预测从单波段DES图像再现的结果CFHTLenS在明亮的幅度和显示更高的相关性与CFHTLenS在较暗的幅度比极大似然模型拟合估计的DES Y1 im 3shape目录。用CNN预测形状参数也非常快，每个星系只需要0.2毫秒，比前向模型拟合提高了4个数量级以上。CNN还可以在使用同一星系的多个图像时准确地预测形状，即使在不同的色带中，也没有额外的计算开销。CNN对微弱的天体也更精确，与DES Y1元校准目录相比，CNN的优势对于蓝色星系比红色星系更明显，DES Y1元校准目录使用riz波段图像拟合单一高斯轮廓。我们证明了在元校准自校准框架内的CNN形状预测产生具有可忽略的乘法偏差的剪切估计，$ m < 10^{-3}$，并且没有显著的PSF泄漏。我们提出的设置适用于当前和下一代弱透镜测量，其中可以在专用的深场中测量更高质量的地面实况形状。
英文摘要：
We present our results from training and evaluating a convolutional neural network (CNN) to predict galaxy shapes from wide-field survey images of the first data release of the Dark Energy Survey (DES DR1). We use conventional shape measurements as ground truth from an overlapping, deeper survey with less sky coverage, the Canada-France Hawaii Telescope Lensing Survey (CFHTLenS). We demonstrate that CNN predictions from single band DES images reproduce the results of CFHTLenS at bright magnitudes and show higher correlation with CFHTLenS at fainter magnitudes than maximum likelihood model fitting estimates in the DES Y1 im3shape catalogue. Prediction of shape parameters with a CNN is also extremely fast, it takes only 0.2 milliseconds per galaxy, improving more than 4 orders of magnitudes over forward model fitting. The CNN can also accurately predict shapes when using multiple images of the same galaxy, even in different color bands, with no additional computational overhead. The CNN is again more precise for faint objects, and the advantage of the CNN is more pronounced for blue galaxies than red ones when compared to the DES Y1 metacalibration catalogue, which fits a single Gaussian profile using riz band images. We demonstrate that CNN shape predictions within the metacalibration self-calibrating framework yield shear estimates with negligible multiplicative bias, $ m < 10^{-3}$, and no significant PSF leakage. Our proposed setup is applicable to current and next generation weak lensing surveys where higher quality ground truth shapes can be measured in dedicated deep fields.
We report the detection of the kinetic Sunyaev-Zel'dovich (kSZ) effect in galaxy clusters with a 4.9 sigma significance using the latest 217 GHz Planck map from data release 4. For the detection, we stacked the Planck map at the positions of 30,431 galaxy clusters from the Wen-Han-Liu (WHL) catalog. To align the sign of the kSZ signals, the line-of-sight velocities of galaxy clusters were estimated with a machine-learning approach, in which the relation between the galaxy distribution around a cluster and its line-of-sight velocity was trained through a convolutional neural network. To train o…
Intrinsic galaxy alignments yield an important contribution to the observed statistics of galaxy shapes. The general bias expansion for galaxy sizes and shapes in three dimensions has been recently described by Vlah, Chisari \& Schmidt using the general perturbative effective field theory (EFT) framework, in analogy to the clustering of galaxies. In this work, we present a formalism that uses the properties of spherical tensors to project galaxy shapes onto the observed sky in the flat-sky approximation and compute the two-point functions at next-to-leading order as well as the leading-order t…
Contamination from galaxy fragments, identified as sources, is a major issue in large photometric galaxy catalogs. In this paper, we prove that this problem can be easily addressed with computer vision techniques. We use image cutouts to train a convolutional neural network (CNN) to identify catalogued sources that are in reality just star formation regions and/or shreds of larger galaxies. The CNN reaches an accuracy ~98% on our testing datasets. We apply this CNN to galaxy catalogs from three amongst the largest surveys available today: the Sloan Digital Sky Survey (SDSS), the DESI Legacy Im…
The shape of relaxed galaxy clusters and the public release of a HST shape measurement code, pyRRG
我们研究了八个动态松弛的星系团的形状与哈勃太空望远镜和钱德拉X射线天文台观测。利用强、弱引力透镜、布里渊星系团的形状和X射线等照度线，研究了四种不同半径的星系团晕的椭圆率。我们发现，代理探测的内部区域的集群是强烈耦合的BCG形状与预测的形状由强引力透镜和X射线等照度线。相反，我们发现没有这样的形状之间的相关性预测的弱透镜和其他三个探针之间的任何耦合的内部和外部区域是弱的。我们还在本文中公开发布了HST弱透镜形状测量代码pyRRG，可直接从PyPi（https：//pypi.org/project/pyRRG/）获得。这段基于Rhodes et al.（2000）的python3.7代码采用了一个基于随机森林的自动化恒星-星系分类器，并输出了科学上有用的产品，例如适用于质量映射算法Lentool的弱透镜星表。
The galaxies form and evolve in the early epochs through the anisotropic merging process along the primary narrow filaments, in the direction of which their shapes become elongated and intrinsically aligned. The nonlinear evolution of the cosmic web broadens the primary filaments, by entangling them with multiple secondary filaments, which has an effect of reducing the anisotropy of the merging process and in consequence weakens the galaxy shape-shape correlations in the later epochs. Assuming that the degree of the nonlinearity and complexity of the cosmic web depends on the nature of dark ma…
We introduce a novel method for reconstructing the projected matter distributions of galaxy clusters with weak-lensing (WL) data based on convolutional neural network (CNN). Training datasets are generated with ray-tracing through cosmological simulations. We control the noise level of the galaxy shear catalog such that it mimics the typical properties of the existing ground-based WL observations of galaxy clusters. We find that the mass reconstruction by our multi-layered CNN with the architecture of alternating convolution and trans-convolution filters significantly outperforms the tradition…
We propose a method of searching for radio sources exhibiting the Sunyaev-Zeldovich effect in the multi-frequency emission maps from the Planck mission data using a convolutional neural network. A catalog for recognizing radio sources is compiled using the GLESP pixelation scheme at the frequencies of 100, 143, 217, 353, and 545 GHz. The quality of the proposed approach is evaluated and the quality of the dependence of model data on the S/N ratio is estimated. We show that the presented neural network approach allows the detection of sources with the Sunyaev-Zeldovich effect. The proposed meth…
We present a detailed study of the shapes and alignments of different galaxy cluster components using hydrodynamical simulations. We compute shape parameters from the Dark Matter (DM) distribution, the galaxy members and the intra-cluster light (ICL). We assess how well the DM cluster shape can be constrained by means of the identified galaxy member positions and the ICL. Further, we address the dilution factor introduced when estimating the cluster elongation using weak-lensing stacking techniques, which arises due to the misalignment between the total surface mass distribution and the distri…
In the standard (classic) approach, galaxy clustering measurements from spectroscopic surveys are compressed into baryon acoustic oscillations and redshift space distortions measurements, which in turn can be compared to cosmological models. Recent works have shown that avoiding this intermediate step and fitting directly the full power spectrum signal (full modelling) leads to much tighter constraints on cosmological parameters. Here we show where this extra information is coming from and extend the classic approach with one additional effective parameter, such that it captures, effectively, …
We present a simulation-based inference framework using a convolutional neural network to infer dynamical masses of galaxy clusters from their observed 3D projected phase-space distribution, which consists of the projected galaxy positions in the sky and their line-of-sight velocities. By formulating the mass estimation problem within this simulation-based inference framework, we are able to quantify the uncertainties on the inferred masses in a straightforward and robust way. We generate a realistic mock catalogue emulating the Sloan Digital Sky Survey (SDSS) Legacy spectroscopic observations…
Towards an optimal extraction of cosmological parameters from galaxy cluster surveys using convolutional neural networks
Università degli Studi di Milano（米兰大学）；INFN, Sezione di Milano（意大利国家核物理研究所米兰分部）；Astronomical Observatory of the Autonomous Region of Aosta Valley (OAVdA), Fondazione Clément Fillietroz - ONLUS（瓦莱达奥斯塔大区天文台（OAVdA），克莱门特·菲雷特罗兹基金会）；INAF, Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；Laboratoire d’Annecy de Physique Theorique (LAPTh), CNRS/USMB（阿讷西理论物理实验室（LAPTh），法国国家科学研究中心/萨瓦大学）
If properly calibrated, the shapes of galaxy clusters can be used to investigate many physical processes: from feedback and quenching of star formation, to the nature of dark matter. Theorists frequently measure shapes using moments of inertia of simulated particles'. We instead create mock (optical, X-ray, strong- and weak-lensing) observations of the twenty-two most massive ($\sim10^{14.7}\,M_\odot$) relaxed clusters in the BAHAMAS simulations. We find that observable measures of shape are rounder. Even when moments of inertia are projected into 2D and evaluated at matched radius, they overe…
Galaxy clusters appear as extended sources in XMM-Newton images, but not all extended sources are clusters. So, their proper classification requires visual inspection with optical images, which is a slow process with biases that are almost impossible to model. We tackle this problem with a novel approach, using convolutional neural networks (CNNs), a state-of-the-art image classification tool, for automatic classification of galaxy cluster candidates. We train the networks on combined XMM-Newton X-ray observations with their optical counterparts from the all-sky Digitized Sky Survey. Our data …
We present a new method to determine the probability distribution of the 3-D shapes of galaxy clusters from the 2-D images using stereology. In contrast to the conventional approach of combining different data sets (such as X-rays, Sunyaev-Zeldovich effect and lensing) to fit a 3-D model of a galaxy cluster for each cluster, our method requires only a single data set, such as X-ray observations or Sunyaev-Zeldovich effect observations, consisting of sufficiently large number of clusters. Instead of reconstructing the 3-D shape of an individual object, we recover the probability distribution fu…
We present the analytical framework for converting projected light distributions with a Sérsic profile into three-dimensional light distributions for stellar systems of arbitrary triaxial shape. The main practical result is the definition of a simple yet robust measure of intrinsic galaxy size: the median radius $r_\mathrm{med}$, defined as the radius of a sphere that contains 50% of the total luminosity or mass, that is, the median distance of a star to the galaxy center. We examine how $r_\mathrm{med}$ depends on projected size measurements as a function of Sérsic index and intrinsic axis ra…
We present a numerical evidence supporting the scenario that the peculiar alignments of the galaxy stellar spins with the major principal axes of the local tidal tensors are produced during the quiescent evolution period when the galaxies experience no recent merger events. Analyzing the merger tree from the TNG300-1 simulation of the IllustrisTNG project, we find the latest merger epochs, $a(z_{m})$, of the galaxies, and create four $a(z_{m})$-selected samples that are controlled to share the identical mass and density distributions. For each sample, we determine the spin and shape vectors of…
The effects of charge transfer inefficiency (CTI) on galaxy shape measurements
我们研究了电荷转移效率（CTI）的影响，在CCD读出星系形状测量所需的弱引力透镜的研究。我们模拟了CCD读出与CTI，如带电粒子辐射损伤所造成的。我们验证我们的模拟实验室辐照CCD的数据。只有电荷陷阱的时间常数相同的顺序，在读出过程中的行传输之间的时间影响星系的形状测量。我们描述了CTI对不同星系种群的影响。我们的基线我们的研究围绕p沟道CCD已被证明具有电荷转移效率高达一个数量级优于几个型号的n沟道CCD设计用于空间应用。我们预测，对于距离读出寄存器最远的星系，星系形状测量的偏差Delta（e）将以每年2.65 +/- 0.02 x 10^（-4）的速度在L2处增加，以获得整个太阳周期的平均累积辐射照射。如果不进行校正，这将在大约4年内消耗暗能量任务的整个形状测量误差预算。其他地方展示的软件缓解技术可以将其降低约10倍，使其效果远低于任务要求。具有比我们研究的更高CTI的CCD可能无法满足未来暗能量任务的要求。我们将讨论如何设计硬件，以进一步减少CTI的影响。
Inferring Halo Mass and Scale Radius of Galaxy Clusters Using Convolutional Neural Networks and Uchuu-UniverseMachine Catalogs
Meiji University（明治大学）；Chiba Institute of Technology（千叶工业大学）；Chiba University（千叶大学）；University of California Merced（加州大学默塞德分校）；National Research Institute of Astronomy and Geophysics（国家天文地球物理研究所）
Using data from the Sloan Digital Sky Survey we study correlations between directions of galaxy angular momenta determined from images of spiral galaxies and various observables derived from the reconstructed initial conditions. We find an apparent systematic effect consistent with galaxy-orientation-dependent selection function. After restricting our attention to the brightest half of the galaxies where this systematic effect is presumed to be absent, we find hints of excess/deficit correlation for two observables. Interestingly, tidal torque theory predicts excess/deficit correlation in exac…
The subject of this paper is to build a physical model describing shape and size correlations of galaxies due to weak gravitational lensing and due to direct tidal interaction of elliptical galaxies with gravitational fields sourced by the cosmic large-scale structure. Setting up a linear intrinsic alignment model for elliptical galaxies which parameterises the reaction of the galaxy to an external tidal shear field is controlled by the velocity dispersion, we predict intrinsic correlations and cross-correlations with weak lensing for both shapes and sizes, juxtaposing both types of spectra wi…
Radio U-Net: a convolutional neural network to detect diffuse radio sources in galaxy clusters and beyond
Istituto di Radio Astronomia, INAF（意大利国家天体物理研究所射电天文研究所）；Dipartimento di Fisica e Astronomia, Universitá di Bologna（博洛尼亚大学物理与天文系）；Hamburger Sternwarte（汉堡天文台）
Galaxy imaging surveys provide us with information on both the galaxy distribution and their shapes. In this paper, we systematically investigate the sensitivity of galaxy shapes to new physics in the initial conditions. For this purpose, we decompose the galaxy shape function into spin components, and compute the contributions to each spin component from both intrinsic alignment and weak lensing. We then consider the angular-dependent primordial non-Gaussianity, which is generated by a non-zero integer spin particle when active during inflation, and show that a galaxy imaging survey essential…
