The GALAH survey: characterization of emission-line stars with spectral modelling using autoencoders

Cotar, Klemen and Zwitter, Tomaz and Traven, Gregor and Bland-Hawthorn, Joss and Buder, Sven and Hayden, Michael R. and Kos, Janez and Lewis, Geraint F. and Martell, Sarah L. and Nordlander, Thomas and Stello, Dennis and Horner, Jonathan and Ting, Yuan-Sen and Zerjal, Marusa and Galah Collaboration, . (2021) The GALAH survey: characterization of emission-line stars with spectral modelling using autoencoders. Monthly Notices of the Royal Astronomical Society, 500 (4). pp. 4849-4865. ISSN 0035-8711


Abstract

We present a neural network autoencoder structure that is able to extract essential latent spectral features from observed spectra and then reconstruct a spectrum from those features. Because of the training with a set of unpeculiar spectra, the network is able to reproduce a spectrum of high signal-to-noise ratio that does not show any spectral peculiarities, even if they are present in an observed spectrum. Spectra generated in this manner were used to identify various emission features among spectra acquired by multiple surveys using the HERMES spectrograph at the Anglo-Australian telescope. Emission features were identified by a direct comparison of the observed and generated spectra. Using the described comparison procedure, we discovered 10 364 candidate spectra with varying intensities (from partially filled-in to well above the continuum) of the Hα/Hβ emission component, produced by different physical mechanisms. A fraction of these spectra belong to the repeated observation that shows temporal variability in their emission profile. Among the emission spectra, we find objects that feature contributions from a nearby rarefied gas (identified through the emission of [N II] and [S II] lines) that was identified in 4004 spectra, which were not all identified as having Hα emission. The positions of identified emission-line objects coincide with multiple known regions that harbour young stars. Similarly, detected nebular emission spectra coincide with visually prominent nebular clouds observable in the red all-sky photographic composites.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Date Deposited: 27 Jan 2021 05:44
Last Modified: 22 Jun 2021 11:06
Uncontrolled Keywords: line: profiles; methods: data analysis; catalogues; stars: activity; stars: emission line; Be; stars: peculiar; Astrophysics - Solar and; Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies; Astrophysics - Instrumentation and Methods for Astrophysics; Physics -; Data Analysis; Statistics and Probability
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.1093/mnras/staa2524
URI: http://eprints.usq.edu.au/id/eprint/40611

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