论文标题

带有神经网络(刚果网)的星系形态Z。 I.成像和光度法优化的准确性和离群分数

Galaxy morphoto-Z with neural Networks (GaZNets). I. Optimized accuracy and outlier fraction from Imaging and Photometry

论文作者

Li, Rui, Napolitano, Nicola R., Feng, Haicheng, Li, Ran, Amaro, Valeria, Xie, Linghua, Tortora, Crescenzo, Bilicki, Maciej, Brescia, Massimo, Cavuoti, Stefano, Radovich, Mario

论文摘要

在大型天空调查的时代,光度红移(Photo-Z)代表了银河发展和宇宙学研究的关键信息。在这项工作中,我们提出了一种新的机器学习(ML)工具,称为Galaxy Morphoto-Z具有神经网络(GHAZNET-1),该工具同时使用图像和多波段光度法测量值来预测Galaxy Redshifts,并具有基于光学成分的标准方法的准确性,精度,精确性和异常分数。作为该工具的第一个应用,我们估算了Kilo-Amegree调查(儿童)中的星系样本的照片。 GAZNET-1在儿童数据版本4(DR4)中收集的$ \ sim140 000 $星系进行了培训和测试,并从不同的调查中获得光谱红移。该样本由Bright(Mag $ \ _ $ auto $ <21 $)和低红移($ Z <0.8 $)系统主导,但是,我们可以使用$ \ sim $ 6500的星系$ 0.8 <z <3 $有效地将培训扩展到更高的红色速度。输入是R波段星系图像以及9波段的幅度和颜色,从孩子的光学光度和Vista Kilo-Degegree红外调查的近红外光度法中的组合目录。通过组合图像和目录,开始的刚刚刚化的绝对偏差可以达到极高的精度(较低的红移= 0.014,对于更高的红移星系的NMAD = 0.041)和较低的异常分数(较低的$ \%$ \%$ \%$ \%$ \%,对于更高的红色速度的$ \%)。与仅使用光度法作为输入的ML代码相比,Gaznet-1还显示了$ \ sim 10-35 $%的精度提高了不同的红移,而$ \ sim $ \ sim $ 45%减少了异常值的分数。我们最终讨论,通过将星系与恒星和活跃的银河核分开,可以将星系的整体照片离群值降低至$ 0.3 $ \%。

In the era of large sky surveys, photometric redshifts (photo-z) represent crucial information for galaxy evolution and cosmology studies. In this work, we propose a new Machine Learning (ML) tool called Galaxy morphoto-Z with neural Networks (GaZNet-1), which uses both images and multi-band photometry measurements to predict galaxy redshifts, with accuracy, precision and outlier fraction superior to standard methods based on photometry only. As a first application of this tool, we estimate photo-z of a sample of galaxies in the Kilo-Degree Survey (KiDS). GaZNet-1 is trained and tested on $\sim140 000$ galaxies collected from KiDS Data Release 4 (DR4), for which spectroscopic redshifts are available from different surveys. This sample is dominated by bright (MAG$\_$AUTO$<21$) and low redshift ($z < 0.8$) systems, however, we could use $\sim$ 6500 galaxies in the range $0.8 < z < 3$ to effectively extend the training to higher redshift. The inputs are the r-band galaxy images plus the 9-band magnitudes and colours, from the combined catalogs of optical photometry from KiDS and near-infrared photometry from the VISTA Kilo-degree Infrared survey. By combining the images and catalogs, GaZNet-1 can achieve extremely high precision in normalized median absolute deviation (NMAD=0.014 for lower redshift and NMAD=0.041 for higher redshift galaxies) and low fraction of outliers ($0.4$\% for lower and $1.27$\% for higher redshift galaxies). Compared to ML codes using only photometry as input, GaZNet-1 also shows a $\sim 10-35$% improvement in precision at different redshifts and a $\sim$ 45% reduction in the fraction of outliers. We finally discuss that, by correctly separating galaxies from stars and active galactic nuclei, the overall photo-z outlier fraction of galaxies can be cut down to $0.3$\%.

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