Machine learning-based photometric classification of galaxies, quasars, emission-line galaxies, and stars

TL;DR

This study demonstrates that machine learning algorithms, especially Random Forest and XGBoost, can accurately classify various astronomical sources like galaxies, quasars, and stars using photometric data from SDSS and ALLWISE, achieving high F1 scores.

Contribution

The paper introduces a comprehensive machine learning approach combining optical and infrared features for photometric classification of diverse astronomical objects, achieving high accuracy.

Findings

RF and XGB achieved 98.93% F1 score in three-class classification.

High accuracy in classifying stars, quasars, and galaxies with F1 scores above 80%.

Combining optical and infrared data improves classification performance.

Abstract

This paper explores the application of machine learning methods for classifying astronomical sources using photometric data, including normal and emission line galaxies (ELGs; starforming, starburst, AGN, broad line), quasars, and stars. We utilized samples from Sloan Digital Sky Survey (SDSS) Data Release 17 (DR17) and the ALLWISE catalog, which contain spectroscopically labeled sources from SDSS. Our methodology comprises two parts. First, we conducted experiments, including three-class, four-class, and seven-class classifications, employing the Random Forest (RF) algorithm. This phase aimed to achieve optimal performance with balanced datasets. In the second part, we trained various machine learning methods, such as $k$-nearest neighbors (KNN), RF, XGBoost (XGB), voting, and artificial neural network (ANN), using all available data based on promising results from the first phase. Our results highlight the effectiveness of combining optical and infrared features, yielding the best performance across all classifiers. Specifically, in the three-class experiment, RF and XGB algorithms achieved identical average F1 scores of 98.93 per~cent on both balanced and unbalanced datasets. In the seven-class experiment, our average F1 score was 73.57 per~cent. Using the XGB method in the four-class experiment, we achieved F1 scores of 87.9 per~cent for normal galaxies (NGs), 81.5 per~cent for ELGs, 99.1 per~cent for stars, and 98.5 per~cent for quasars (QSOs). Unlike classical methods based on time-consuming spectroscopy, our experiments demonstrate the feasibility of using automated algorithms on carefully classified photometric data. With more data and ample training samples, detailed photometric classification becomes possible, aiding in the selection of follow-up observation candidates.