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arXiv · 2506.22547

MOSDEF-3D: Keck/OSIRIS Maps of the Ionized ISM in $z \sim 2$ Galaxies

Natalie Lam·Alice E. Shapley·Ryan L. Sanders·Tuan Do·Tucker Jones·Alison Coil·Mariska Kriek·Bahram Mobasher·Naveen A. Reddy·Brian Siana·Leonardo Clarke
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Abstract

We present spatially-resolved rest-frame optical emission line maps of four galaxies at $z \sim 2$ observed with Keck/OSIRIS to study the physical conditions of the ISM at Cosmic Noon. Our analysis of strong emission line ratios in these galaxies reveals an offset from the local star-forming locus on the BPT diagram, but agrees with other star-forming galaxies at similar redshifts. Despite the offset towards higher [O III]$\lambda5008$/H$β$ and [N II]$\lambda6585$/H$α$, these strong-line ratios remain consistent with or below the maximum starburst threshold even in the inner $\sim 1$ kpc region of the galaxies, providing no compelling evidence for central AGN activity. The galaxies also exhibit flat radial gas-phase metallicity gradients, consistent with previous studies of $z \sim 2$ galaxies and suggesting efficient radial mixing possibly driven by strong outflows from intense star formation. Overall, our results reveal the highly star-forming nature of these galaxies, with the potential to launch outflows that flatten metallicity gradients through significant radial gas mixing. Future observations with JWST/NIRSpec are crucial to detect fainter emission lines at higher spatial resolution to further constrain the physical processes and ionization mechanisms that shape the ISM during Cosmic Noon.

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Natalie Lam, Alice E. Shapley, Ryan L. Sanders, Tuan Do, Tucker Jones, Alison Coil, Mariska Kriek, Bahram Mobasher, Naveen A. Reddy, Brian Siana, Leonardo Clarke. 2026-03-26. MOSDEF-3D: Keck/OSIRIS Maps of the Ionized ISM in $z \sim 2$ Galaxies. https://arxiv.org/abs/2506.22547

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