COSMOS2020: Manifold learning to estimate physical parameters in large galaxy surveys

I. Davidzon*, K. Jegatheesan, O. Ilbert, S. de la Torre, S. K. Leslie, C. Laigle, S. Hemmati, D. C. Masters, D. Blanquez-Sese, O. B. Kauffmann, G. E. Magdis, H. J. McCracken, B. Mobasher, A. Moneti, D. B. Sanders, M. Shuntov, S. Toft, J. R. Weaver, K. Malek

*Corresponding author for this work

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Abstract

We present a novel method for estimating galaxy physical properties from spectral energy distributions (SEDs) as an alternative to template fitting techniques and based on self-organizing maps (SOMs) to learn the high-dimensional manifold of a photometric galaxy catalog. The method has previously been tested with hydrodynamical simulations in Davidzon et al. (2019, MNRAS, 489, 4817), however, here it is applied to real data for the first time. It is crucial for its implementation to build the SOM with a high-quality panchromatic data set, thus we selected "COSMOS2020" galaxy catalog for this purpose. After the training and calibration steps with COSMOS2020, other galaxies can be processed through SOMs to obtain an estimate of their stellar mass and star formation rate (SFR). Both quantities resulted in a good agreement with independent measurements derived from more extended photometric baseline and, in addition, their combination (i.e., the SFR vs. stellar mass diagram) shows a main sequence of star-forming galaxies that is consistent with the findings of previous studies. We discuss the advantages of this method compared to traditional SED fitting, highlighting the impact of replacing the usual synthetic templates with a collection of empirical SEDs built by the SOM in a "data-driven" way. Such an approach also allows, even for extremely large data sets, for an efficient visual inspection to identify photometric errors or peculiar galaxy types. While also considering the computational speed of this new estimator, we argue that it will play a valuable role in the analysis of oncoming large-area surveys such as Euclid of the Legacy Survey of Space and Time at the Vera C. Rubin Telescope.
Original languageEnglish
Article numberA34
JournalAstronomy and Astrophysics
Volume665
Number of pages22
ISSN0004-6361
DOIs
Publication statusPublished - 2022

Keywords

  • Galaxies: fundamental parameters
  • Galaxies: star formation
  • Galaxies: stellar content
  • Methods: observational
  • Astronomical databases: miscellaneous

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