SDSS Galaxy Subset

The Sloan Digital Sky Survey (SDSS) is a comprehensive survey of the northern sky. This dataset contains a subset of this survey, of 60247 objects classified as galaxies, it includes a CSV file with a collection of information and a set of files for each object, namely JPG image files, FITS and spectra data. This dataset is used to train and explore the astromlp-models collection of deep learning models for galaxies characterisation. The dataset includes a CSV data file where each row is an object from the SDSS database, and with the following columns (note that some data may not be available for all objects): <strong>objid</strong>: unique SDSS object identifier <strong>mjd</strong>: MJD of observation <strong>plate</strong>: plate identifier <strong>tile</strong>: tile identifier <strong>fiberid</strong>: fiber identifier <strong>run</strong>: run number <strong>rerun</strong>: rerun number <strong>camcol</strong>: camera column <strong>field</strong>: field number <strong>ra</strong>: right ascension <strong>dec</strong>: declination <strong>class</strong>: spectroscopic class (only objetcs with GALAXY are included) <strong>subclass</strong>: spectroscopic subclass <strong>modelMag_u</strong>: better of DeV/Exp magnitude fit for band u <strong>modelMag_g</strong>: better of DeV/Exp magnitude fit for band g <strong>modelMag_r</strong>: better of DeV/Exp magnitude fit for band r <strong>modelMag_i</strong>: better of DeV/Exp magnitude fit for band i <strong>modelMag_z</strong>: better of DeV/Exp magnitude fit for band z <strong>redshift</strong>: final redshift from SDSS data z <strong>stellarmass</strong>: stellar mass extracted from the eBOSS Firefly catalog <strong>w1mag</strong>: WISE W1 "standard" aperture magnitude <strong>w2mag</strong>: WISE W2 "standard" aperture magnitude <strong>w3mag</strong>: WISE W3 "standard" aperture magnitude <strong>w4mag</strong>: WISE W4 "standard" aperture magnitude <strong>gz2c_f</strong>: Galaxy Zoo 2 classification from Willett et al 2013 <strong>gz2c_s</strong>: simplified version of Galaxy Zoo 2 classification (labels set) Besides the CSV file a set of directories are included in the dataset, in each directory you'll find a list of files named after the <strong>objid </strong>column from the CSV file, with the corresponding data, the following directories tree is available: <pre><code class="language-bash">sdss-gs/ ├── data.csv ├── fits ├── img ├── spectra └── ssel</code></pre> Where, each directory contains: <strong>img</strong>: RGB images from the object in JPEG format, 150x150 pixels, generated using the SkyServer DR16 API <strong>fits</strong>: FITS data subsets around the object across the u, g, r, i, z bands; cut is done using the ImageCutter library <strong>spectra</strong>: full best fit spectra data from SDSS between 4000 and 9000 wavelengths <strong>ssel</strong>: best fit spectra data from SDSS for specific selected intervals of wavelengths discussed by Sánchez Almeida 2010 <strong>Changelog</strong> v0.0.3 - Increase number of objects to ~80k. v0.0.2 - Increase number of objects to ~60k. v0.0.1 - Initial import.

斯隆数字巡天（Sloan Digital Sky Survey，SDSS）是一项覆盖北天的综合性巡天项目。本数据集为该巡天的子集，包含60247个被归类为星系的天体，内含一个存储多维度信息的CSV文件，以及对应每个天体的一系列文件：JPEG格式图像文件、FITS格式数据与光谱数据。本数据集可用于训练与探索用于星系特征表征的astromlp-models深度学习模型集。

该数据集附带的CSV数据文件中，每一行对应SDSS数据库中的一个天体，部分天体可能存在数据缺失情况，其包含的字段如下：<strong>objid</strong>：SDSS天体唯一标识符；<strong>mjd</strong>：观测修正儒略日（Modified Julian Date，MJD）；<strong>plate</strong>：巡天板标识符；<strong>tile</strong>：天区瓦片标识符；<strong>fiberid</strong>：光纤标识符；<strong>run</strong>：观测运行编号；<strong>rerun</strong>：重处理编号；<strong>camcol</strong>：相机柱面编号；<strong>field</strong>：视场编号；<strong>ra</strong>：赤经（right ascension）；<strong>dec</strong>：赤纬（declination）；<strong>class</strong>：光谱学分类（仅包含被标记为GALAXY的天体）；<strong>subclass</strong>：光谱学子类；<strong>modelMag_u</strong>：u波段DeV/Exp拟合的最优星等；<strong>modelMag_g</strong>：g波段DeV/Exp拟合的最优星等；<strong>modelMag_r</strong>：r波段DeV/Exp拟合的最优星等；<strong>modelMag_i</strong>：i波段DeV/Exp拟合的最优星等；<strong>modelMag_z</strong>：z波段DeV/Exp拟合的最优星等；<strong>redshift</strong>：基于SDSS数据得到的最终红移z；<strong>stellarmass</strong>：从eBOSS Firefly星表（eBOSS Firefly catalog）中提取的恒星质量；<strong>w1mag</strong>：WISE（Wide-field Infrared Survey Explorer）W1波段“标准”孔径星等；<strong>w2mag</strong>：WISE W2波段“标准”孔径星等；<strong>w3mag</strong>：WISE W3波段“标准”孔径星等；<strong>w4mag</strong>：WISE W4波段“标准”孔径星等；<strong>gz2c_f</strong>：Willett等人2013年研究中的星系动物园2（Galaxy Zoo 2，GZ2）分类结果；<strong>gz2c_s</strong>：星系动物园2分类的简化版本（标签集）。

除CSV文件外，数据集还包含多个目录，各目录下的文件均以CSV文件中的<strong>objid</strong>字段命名，存储对应天体的相关数据。数据集的目录结构如下：
<pre><code class="language-bash">sdss-gs/
├── data.csv
├── fits
├── img
├── spectra
└── ssel</code></pre>
各目录的详细说明如下：<strong>img</strong>：使用SkyServer DR16 API生成的天体RGB图像，格式为JPEG，分辨率为150×150像素；<strong>fits</strong>：覆盖u、g、r、i、z波段的天体周边FITS数据子集，通过ImageCutter库完成截切操作；<strong>spectra</strong>：SDSS提供的最优拟合光谱数据，波长范围覆盖4000至9000；<strong>ssel</strong>：Sánchez Almeida 2010年研究中讨论的特定波长区间的SDSS最优拟合光谱数据。

更新日志
v0.0.3：将天体数量提升至约80000个；
v0.0.2：将天体数量提升至约60000个；
v0.0.1：初始导入版本。