Spatial Variations In Aromatic Hydrocarbon Emission In A Dust-rich Galaxy

By Keith Cowing
Press Release
June 7, 2023
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Spatial Variations In Aromatic Hydrocarbon Emission In A Dust-rich Galaxy
Mid- and far-infrared continuum and PAH emission from SPT0418-47. a, Continuum-subtracted 3.3μm PAH emission integrated over the wavelength range indicated in Fig. 1. The range in integrated intensity is provided in the colorbar. b, Rest-frame 3.1μm continuum image created from the PAH-free channels of the MIRI/MRS data. The range in intensity is shown at right. Stellar emission from the foreground lens galaxy is visible at the center of the lensed Einstein ring. c, Rest-frame 160μm continuum image from ALMA matched to the 0.65” spatial resolution of the MIRI/MRS data (Methods). The color scale at right shows the flux density per synthesized beam, the shape of which is shown at lower left. Contours of the 160μm flux density are repeated in panels a-c at levels of 10, 30, 50, 70, and 90 times the noise level of 0.12mJy per beam. — astro-ph.GA

Dust grains absorb half of the radiation emitted by stars throughout the history of the universe, re-emitting this energy at infrared wavelengths.

Polycyclic aromatic hydrocarbons (PAHs) are large organic molecules that trace millimeter-size dust grains and regulate the cooling of the interstellar gas within galaxies. Observations of PAH features in very distant galaxies have been difficult due to the limited sensitivity and wavelength coverage of previous infrared telescopes. Here we present JWST observations that detect the 3.3um PAH feature in a galaxy observed less than 1.5 billion years after the Big Bang.

The high equivalent width of the PAH feature indicates that star formation, rather than black hole accretion, dominates the infrared emission throughout the galaxy. The light from PAH molecules, large dust grains, and stars and hot dust are spatially distinct from one another, leading to order-of-magnitude variations in the PAH equivalent width and the ratio of PAH to total infrared luminosity across the galaxy.

The spatial variations we observe suggest either a physical offset between the PAHs and large dust grains or wide variations in the local ultraviolet radiation field. Our observations demonstrate that differences in the emission from PAH molecules and large dust grains are a complex result of localized processes within early galaxies.

Justin S. Spilker, Kedar A. Phadke, Manuel Aravena, Melanie Archipley, Matthew B. Bayliss, Jack E. Birkin, Matthieu Bethermin, James Burgoyne, Jared Cathey, Scott C. Chapman, Hakon Dahle, Anthony H. Gonzalez, Gayathri Gururajan, Christopher C. Hayward, Yashar D. Hezaveh, Ryley Hill, Taylor A. Hutchison, Keunho J. Kim, Seonwoo Kim, David Law, Ronan Legin, Matthew A. Malkan, Daniel P. Marrone, Eric J. Murphy, Desika Narayanan, Alex Navarre, Grace M. Olivier, Jeffrey A. Rich, Jane R. Rigby, Cassie Reuter, James E. Rhoads, Keren Sharon, J.D. T. Smith, Manuel Solimano, Nikolaus Sulzenauer, Joaquin D. Vieira, Axel Weiss, Katherine E. Whitaker

Comments: Published in Nature 5 June 2023 at this https URL. MIRI MRS reduction notebook is available at this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2306.03152 [astro-ph.GA] (or arXiv:2306.03152v1 [astro-ph.GA] for this version)
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Submission history
From: Justin Spilker
[v1] Mon, 5 Jun 2023 18:06:16 UTC (1,358 KB)
Astrobiology, Astrochemistry

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻