Trump_2023_ApJ_945_35.pdf (1.25 MB)
The physical conditions of emission-line galaxies at cosmic dawn from JWST/NIRSpec spectroscopy in the SMACS 0723 early release observations
journal contribution
posted on 2023-06-10, 06:50 authored by Jonathan R Trump, Pablo A Haro, Raymond C Simons, Bren E Backhaus, Ricardo O Amorín, Mark Dickinson, Vital Fernández, Casey Papovich, David C Nicholls, Lisa J Kewley, Samantha W Brunker, John J Salzer, Stephen WilkinsStephen Wilkins, Omar Almaini, othersWe present rest-frame optical emission-line flux ratio measurements for five z > 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliable relative flux calibration of emission lines that are closely separated in wavelength, despite the uncertain absolute spectrophotometry of the current version of the reductions. Compared to z ~ 3 galaxies in the literature, the z > 5 galaxies have similar [O iii]?5008/Hß ratios, similar [O iii]?4364/H? ratios, and higher (~0.5 dex) [Ne III]?3870/[O II]?3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [Ne III]?3870/[O II]?3728, [O iii]?4364/H?, and [O iii]?5008/Hß emission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( log ( Q ) ? 8 - 9 , units of cm s-1), low metallicity (Z/Z ? ? 0.2), and very high pressure ( log ( P / k ) ? 8 - 9 , units of cm-3). The combination of [O iii]?4364/H? and [O iii]?(4960 + 5008)/Hß line ratios indicate very high electron temperatures of 4.1 < log ( T e / K ) < 4.4 , further implying metallicities of Z/Z ? ? 0.2 with the application of low-redshift calibrations for “T e -based” metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.
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Astrophysical JournalISSN
0004-637XPublisher
American Astronomical SocietyExternal DOI
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1Volume
945Page range
a35 1-11Department affiliated with
- Physics and Astronomy Publications
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- Yes
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2023-04-24First Open Access (FOA) Date
2023-04-24First Compliant Deposit (FCD) Date
2023-04-24Usage metrics
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