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
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 $0.3$\%.