The Astrophysical Journal Letters (Jan 2023)

PHANGS–JWST First Results: The 21 μm Compact Source Population

  • Hamid Hassani,
  • Erik Rosolowsky,
  • Adam K. Leroy,
  • Médéric Boquien,
  • Janice C. Lee,
  • Ashley T. Barnes,
  • Francesco Belfiore,
  • F. Bigiel,
  • Yixian Cao,
  • Mélanie Chevance,
  • Daniel A. Dale,
  • Oleg V. Egorov,
  • Eric Emsellem,
  • Christopher M. Faesi,
  • Kathryn Grasha,
  • Jaeyeon Kim,
  • Ralf S. Klessen,
  • Kathryn Kreckel,
  • J. M. Diederik Kruijssen,
  • Kirsten L. Larson,
  • Sharon E. Meidt,
  • Karin M. Sandstrom,
  • Eva Schinnerer,
  • David A. Thilker,
  • Elizabeth J. Watkins,
  • Bradley C. Whitmore,
  • Thomas G. Williams

DOI
https://doi.org/10.3847/2041-8213/aca8ab
Journal volume & issue
Vol. 944, no. 2
p. L21

Abstract

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We use PHANGS–James Webb Space Telescope (JWST) data to identify and classify 1271 compact 21 μ m sources in four nearby galaxies using MIRI F2100W data. We identify sources using a dendrogram-based algorithm, and we measure the background-subtracted flux densities for JWST bands from 2 to 21 μ m. Using the spectral energy distribution (SED) in JWST and HST bands plus ALMA and MUSE/VLT observations, we classify the sources by eye. Then we use this classification to define regions in color–color space and so establish a quantitative framework for classifying sources. We identify 1085 sources as belonging to the ISM of the target galaxies with the remainder being dusty stars or background galaxies. These 21 μ m sources are strongly spatially associated with H ii regions (>92% of sources), while 74% of the sources are coincident with a stellar association defined in the HST data. Using SED fitting, we find that the stellar masses of the 21 μ m sources span a range of 10 ^2 –10 ^4 M _⊙ with mass-weighted ages down to 2 Myr. There is a tight correlation between attenuation-corrected H α and 21 μ m luminosity for L _ν _,F2100W > 10 ^19 W Hz ^−1 . Young embedded source candidates selected at 21 μ m are found below this threshold and have M _⋆ < 10 ^3 M _⊙ .

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