TY - JOUR
T1 - The Physical Conditions of Emission-line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations
AU - CEERS
AU - Trump, Jonathan R.
AU - Haro, Pablo Arrabal
AU - Simons, Raymond C.
AU - Backhaus, Bren E.
AU - Amorín, Ricardo O.
AU - Dickinson, Mark
AU - Fernández, Vital
AU - Papovich, Casey
AU - Nicholls, David C.
AU - Kewley, Lisa J.
AU - Brunker, Samantha W.
AU - Salzer, John J.
AU - Almaini, Omar
AU - Bagley, Micaela B.
AU - Berg, Danielle A.
AU - Bhatawdekar, Rachana
AU - Bisigello, Laura
AU - Buat, Véronique
AU - Burgarella, Denis
AU - Calabrò, Antonello
AU - Casey, Caitlin M.
AU - Ciesla, Laure
AU - Cleri, Nikko J.
AU - Cole, Justin W.
AU - Cooper, M. C.
AU - Cooray, Asantha R.
AU - Costantin, Luca
AU - Croton, Darren
AU - Ferguson, Henry C.
AU - Finkelstein, Steven L.
AU - Fujimoto, Seiji
AU - Gardner, Jonathan P.
AU - Gawiser, Eric
AU - Giavalisco, Mauro
AU - Grazian, Andrea
AU - Grogin, Norman A.
AU - Hathi, Nimish P.
AU - Hirschmann, Michaela
AU - Holwerda, Benne W.
AU - Huertas-Company, Marc
AU - Hutchison, Taylor A.
AU - Jogee, Shardha
AU - Juneau, Stéphanie
AU - Jung, Intae
AU - Kartaltepe, Jeyhan S.
AU - Kirkpatrick, Allison
AU - Kocevski, Dale D.
AU - Koekemoer, Anton M.
AU - Lotz, Jennifer M.
AU - Wuyts, Stijn
N1 - This work is supported by NASA grants JWST-ERS-01345 and JWST-AR-01721. J.R.T. and B.E.B. additionally acknowledge support from NSF grant CAREER-1945546. R.C.S. appreciates support from a Giacconi Fellowship at the Space Telescope Science Institute. R.A. acknowledges support from Fondecyt Regular 1202007. P.G.P.-G. acknowledges support from grant PGC2018-093499-B-I00 funded by MCIN/AEI/ 10.13039/501100011033. A.Y. is supported by an appointment to the NASA Postdoctoral Program (NPP) at NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA.
PY - 2023/3/1
Y1 - 2023/3/1
N2 - 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 ( 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.
AB - 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 ( 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.
UR - http://www.scopus.com/inward/record.url?scp=85149729541&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/acba8a
DO - 10.3847/1538-4357/acba8a
M3 - Article
SN - 0004-637X
VL - 945
SP - 35
EP - 46
JO - The Astrophysical Journal
JF - The Astrophysical Journal
IS - 1
M1 - 35
ER -