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

Creators: Young, Jason¹; Pope, Alexandra¹; Sajina, Anna²; Yan, Lin³; Gonçalves, Thiago S⁴; Eleazer, Miriam¹; Alberts, Stacey⁵; Armus, Lee^{3, 6}; Bonato, Matteo⁷; Dale, Daniel A.⁸; Farrah, Duncan⁹; Ferkinhoff, Carl¹⁰; Hayward, Christopher C.¹¹; McKinney, Jed¹²; Murphy, Eric J.¹³; Nesvadba, Nicole¹⁴; Ogle, Patrick¹⁵; Sajkov, Leonid²; Veilleux, Sylvain¹⁶

1. University of Massachusetts System
2. Tufts University
3. California Institute of Technology
4. Valongo Observatory
5. University of Arizona
6. Infrared Processing and Analysis Center
7. Istituto di Radioastronomia di Bologna
8. University of Wyoming
9. University of Hawaii at Manoa
10. Winona State University
11. Flatiron Institute
12. The University of Texas at Austin
13. National Radio Astronomy Observatory
14. Lagrange Laboratory
15. Space Telescope Science Institute
16. University of Maryland, College Park

Abstract

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.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We thank the anonymous reviewer for their thoughtful comments, which we believe have improved our manuscript. We thank the following individuals who helped with the analysis of these data: David Law, Jane Morrison, Dick Shaw, Bryan Holler, Beth Sargent, and Sean Linden. Based on observations with the NASA/ESA/CSA James Webb Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-03127. Support for program No. JWST-GO-01762 was provided through a grant from the STScI under NASA contract NAS5-03127. The Flatiron Institute is supported by the Simons Foundation.

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