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Oscar Agertz. Profile photo.

Oscar Agertz

Associate Professor / Senior university lecturer / Wallenberg Academy Fellow

Oscar Agertz. Profile photo.

How complex are galaxies? A non-parametric estimation of the intrinsic dimensionality of wide-band photometric data

Author

  • Corentin Cadiou
  • Clotilde Laigle
  • Oscar Agertz

Summary, in English

Galaxies are complex objects, yet the number of independent parameters to describe them remains unknown. We present here a non-parametric method to estimate the intrinsic dimensionality of large data sets. We apply it to wide-band photometric data drawn from the COSMOS2020 catalogue and a comparable mock catalogue from the HORIZON-AGN simulation. Our galaxy catalogues are limited in signal-to-noise ratio (SNR) in all optical and near-infrared bands. Our results reveal that most of the variance in the wide-band photometry of this galaxy sample can be described with at most 4.3 ± 0.5 independent parameters for star-forming galaxies and 2.9 ± 0.2 for passive ones, both in the observed and simulated catalogues. We identify one of these parameters to be noise-driven, and recover that stellar mass and redshift are two key independent parameters driving the magnitudes. Our findings support the idea that wide-band photometry does not provide more than one additional independent parameter for star-forming galaxies. Although our sample is not mass-limited and may miss some passive galaxies due to our cut in SNR, our work suggests that dimensionality reduction techniques may be effectively used to explore and analyse wide-band photometric data, provided the used latent space is at least four-dimensional.

Department/s

  • Astrophysics
  • eSSENCE: The e-Science Collaboration

Publishing year

2025-02

Language

English

Pages

1869-1878

Publication/Series

Monthly Notices of the Royal Astronomical Society

Volume

537

Issue

2

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • galaxies: formation
  • galaxies: fundamental parameters
  • methods: data analysis

Status

Published

ISBN/ISSN/Other

  • ISSN: 0035-8711