Massive young stellar objects in the Local Group irregular galaxy NGC6822 identified using machine learning

Kinson, David A; Oliveira, Joanna; Van Loon, Jacco

Abstract

We present a supervised machine learning methodology to classify stellar populations in the Local Group dwarf-irregular galaxy NGC?6822. Near-IR colours (J - H, H - K, and J - K), K-band magnitudes and far-IR surface brightness (at 70 and 160?µm) measured from Spitzer and Herschel images are the features used to train a Probabilistic Random Forest (PRF) classifier. Point-sources are classified into eight target classes: young stellar objects (YSOs), oxygen- and carbon-rich asymptotic giant branch stars, red giant branch and red supergiant stars, active galactic nuclei, massive main-sequence stars, and Galactic foreground stars. The PRF identifies sources with an accuracy of ~?90?per?cent across all target classes rising to ~96?per?cent for YSOs. We confirm the nature of 125 out of 277 literature YSO candidates with sufficient feature information, and identify 199 new YSOs and candidates. Whilst these are mostly located in known star-forming regions, we have also identified new star formation sites. These YSOs have mass estimates between ~15 and 50?M?, representing the most massive YSO population in NGC?6822. Another 82 out of 277 literature candidates are definitively classified as non-YSOs by the PRF analysis. We characterize the star formation environment by comparing the spatial distribution of YSOs to those of gas and dust using archival images. We also explore the potential of using (unsupervised) t-distributed stochastic neighbour embedding maps for the identification of the same stellar population classified by the PRF.

Citation

Kinson, D. A., Oliveira, J., & Van Loon, J. (2021). Massive young stellar objects in the Local Group irregular galaxy NGC6822 identified using machine learning. Monthly Notices of the Royal Astronomical Society, 507(4), 5106 - 5131. https://doi.org/10.1093/mnras/stab2386

• Journal Article Type: Article
• Acceptance Date: Aug 16, 2021
• Online Publication Date: Aug 19, 2021
• Publication Date: 2021-11
• Publicly Available Date: May 30, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 507
• Issue: 4
• Pages: 5106 - 5131
• DOI: https://doi.org/10.1093/mnras/stab2386
• Publisher URL: https://academic.oup.com/mnras/article/507/4/5106/6354794