Halfway to the Peak: Spatially Resolved Star Formation and Kinematics in a z = 0.54 Dusty Galaxy with JWST/MIRI

Jason Young, Alexandra Pope, Anna Sajina, Lin Yan, Thiago S. Gonçalves, Miriam Eleazer, Stacey Alberts, Lee Armus, Matteo Bonato, Daniel A. Dale, Duncan Farrah, Carl Ferkinhoff, Christopher C. Hayward, Jed McKinney, Eric J. Murphy, Nicole Nesvadba, Patrick Ogle, Leonid Sajkov, Sylvain Veilleux

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We present JWST Mid-InfraRed Instrument/Medium-Resolution Spectrometer (MIRI/MRS) observations of an infrared luminous disk galaxy, FLS1, at z ∼ 0.54. With a lookback time of 5 Gyr, FLS1 is chronologically at the midpoint between the peak epoch of star formation and the present day. The MRS data provide maps of the atomic fine structure lines [Ar ii]6.99, [Ar iii]8.99, [Ne ii]12.81, and [Ne iii]15.55 μm, polycyclic aromatic hydrocarbon (PAH) features at 3.3, 6.2, and 11.3 μm, and the warm molecular gas indicators H2S(5) and H2S(3); all these emission features are spatially resolved. We find that the PAH emission is more extended along the northern side of the galaxy when compared to the well-studied star formation tracer [Ne ii]. The H2 rotational lines, which are shock indicators, are strongest and most extended on the southern side of the galaxy. [Ar ii] is the second brightest fine structure line detected in FLS1 and we show that it is a useful kinematic probe that can be detected with JWST out to z ∼ 3. Velocity maps of [Ar ii] show a rotating disk with signs of turbulence. Our results provide an example of how spatially resolved mid-infrared spectroscopy can allow us to better understand the star formation and interstellar medium conditions in a galaxy halfway back to the peak epoch of galaxy evolution.

Original languageEnglish (US)
Article numberL5
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Nov 1 2023

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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