Skip to main content

Research Repository

Advanced Search

The Physical Conditions of Emission-line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations

Trump, Jonathan R.; Haro, Pablo Arrabal; Simons, Raymond C.; Backhaus, Bren E.; Amorín, Ricardo O.; Dickinson, Mark; Fernández, Vital; Papovich, Casey; Nicholls, David C.; Kewley, Lisa J.; Brunker, Samantha W.; Salzer, John J.; Wilkins, Stephen M.; Almaini, Omar; Bagley, Micaela B.; Berg, Danielle A.; Bhatawdekar, Rachana; Bisigello, Laura; Buat, Véronique; Burgarella, Denis; Calabrò, Antonello; Casey, Caitlin M.; Ciesla, Laure; Cleri, Nikko J.; Cole, Justin W.; Cooper, M. C.; Cooray, Asantha R.; Costantin, Luca; Croton, Darren; Ferguson, Henry C.; Finkelstein, Steven L.; Fujimoto, Seiji; Gardner, Jonathan P.; Gawiser, Eric; Giavalisco, Mauro; Grazian, Andrea; Grogin, Norman A.; Hathi, Nimish P.; Hirschmann, Michaela; Holwerda, Benne W.; Huertas-Company, Marc; Hutchison, Taylor A.; Jogee, Shardha; Juneau, Stéphanie; Jung, Intae; Kartaltepe, Jeyhan S.; Kirkpatrick, Allison; Kocevski, Dale D.; Koekemoer, Anton M.; Lotz, Jennifer M.; Lucas, Ray A.; Magnelli, Benjamin; Matharu, Jasleen; Pé...

The Physical Conditions of Emission-line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations Thumbnail


Jonathan R. Trump

Pablo Arrabal 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 M. Wilkins

Professor of Astrophysics

Micaela B. Bagley

Danielle A. Berg

Rachana Bhatawdekar

Laura Bisigello

Véronique Buat

Denis Burgarella

Antonello Calabrò

Caitlin M. Casey

Laure Ciesla

Nikko J. Cleri

Justin W. Cole

M. C. Cooper

Asantha R. Cooray

Luca Costantin

Darren Croton

Henry C. Ferguson

Steven L. Finkelstein

Seiji Fujimoto

Jonathan P. Gardner

Eric Gawiser

Mauro Giavalisco

Andrea Grazian

Norman A. Grogin

Nimish P. Hathi

Michaela Hirschmann

Benne W. Holwerda

Marc Huertas-Company

Taylor A. Hutchison

Shardha Jogee

Stéphanie Juneau

Intae Jung

Jeyhan S. Kartaltepe

Allison Kirkpatrick

Dale D. Kocevski

Anton M. Koekemoer

Jennifer M. Lotz

Ray A. Lucas

Benjamin Magnelli

Jasleen Matharu

Pablo G. Pérez-González

Nor Pirzkal

Marc Rafelski

Caitlin Rose

Lise Marie Seillé

Rachel S. Somerville

Amber N. Straughn

Sandro Tacchella

Brittany N. Vanderhoof

Benjamin J. Weiner

Stijn Wuyts

L. Y. Aaron Yung

Jorge A. Zavala


We 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]λ5008/Hβ ratios, similar [O iii]λ4364/Hγ ratios, and higher (∼0.5 dex) [Ne III]λ3870/[O II]λ3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [Ne III]λ3870/[O II]λ3728, [O iii]λ4364/Hγ, and [O iii]λ5008/Hβ 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]λ4364/Hγ and [O iii]λ(4960 + 5008)/Hβ line ratios indicate very high electron temperatures of 4.1<log(Te/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.

Journal Article Type Article
Acceptance Date Dec 18, 2022
Online Publication Date Mar 6, 2023
Publication Date Mar 1, 2023
Deposit Date Jan 11, 2023
Publicly Available Date Mar 1, 2023
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 945
Issue 1
Article Number 35
Keywords Emission line galaxies; galaxies; high red-shift galaxies
Public URL
Publisher URL


You might also like

Downloadable Citations