NGDEEP: The Star Formation and Ionization Properties of Galaxies at 1.7 < z < 3.4

NGDEEP: The Star Formation and Ionization Properties of Galaxies at 1.7 < z < 3.4

We use JWST/NIRISS slitless spectroscopy from the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey to investigate the physical condition of 178 star-forming galaxies at 1.7 <  z  < 3.4. At these redshifts, the deep NGDEEP NIRISS slitless spectroscopy covers the [O ii ] λλ...

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Main Authors: Lu Shen, Casey Papovich, Jasleen Matharu, Nor Pirzkal, Weida Hu, Danielle A. Berg, Micaela B. Bagley, Bren E. Backhaus, Nikko J. Cleri, Mark Dickinson, Steven L. Finkelstein, Nimish P. Hathi, Marc Huertas-Company, Taylor A. Hutchison, Mauro Giavalisco, Norman A. Grogin, Anne E. Jaskot, Intae Jung, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Jennifer M. Lotz, Pablo G. Pérez-González, Barry Rothberg, Raymond C. Simons, Brittany N. Vanderhoof, L. Y. Aaron Yung
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal Letters
Subjects:
Star formation
High-redshift galaxies
Galaxy stellar content
Galaxy evolution
Online Access:https://doi.org/10.3847/2041-8213/adb28d
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Summary:We use JWST/NIRISS slitless spectroscopy from the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey to investigate the physical condition of 178 star-forming galaxies at 1.7 <  z  < 3.4. At these redshifts, the deep NGDEEP NIRISS slitless spectroscopy covers the [O ii ] λλ 3726,3729, [O iii ] λλ 4959,5007, H β and H α emission features for galaxies with stellar masses $\mathrm{log}({{M}}_{* }/{{M}}_{\odot })\gtrsim 7$ , nearly a factor of 100 lower than previous studies. We focus on the [O ii ]/[O iii ] (O _32 ) ratio which is primarily sensitive to the ionization state and with a secondary dependence on the gas-phase metallicity of the interstellar medium. We find significant (≳5 σ ) correlations between the O _32 ratio and galaxy properties as O _32 increases with decreasing stellar mass, decreasing star formation rate (SFR), increasing specific SFR (sSFR ≡ SFR/ M _* ), and increasing equivalent width (EW) of H α and H β . These trends suggest a tight connection between the ionization parameter and these galaxy properties. Galaxies at z  ∼ 2–3 exhibit a higher O _32 than local normal galaxies with the same stellar masses and SFRs, indicating that they have a higher ionization parameter and lower metallicity than local normal galaxies. In addition, we observe a mild evolutionary trend in the O _32 –EW(H β ) relation from z  ∼ 0 to z  ≳ 5, where higher redshift galaxies show increased O _32 and EW, with possibly higher O _32 at fixed EW. We argue that both the enhanced recent star formation activity and the higher star formation surface density may contribute to the increase in O _32 and the ionization parameter.
ISSN:2041-8205

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