The AURORA survey: the evolution of multiphase electron densities at high redshift

Michael W. Topping; Ryan L. Sanders; Alice E. Shapley; Anthony J. Pahl; Naveen A. Reddy; Daniel P. Stark; Danielle A. Berg; Leonardo Clarke; Fergus Cullen; James S. Dunlop; Richard S. Ellis; N. M.Förster Schreiber; Garth D. Illingworth; Tucker Jones; Desika Narayanan; Max Pettini; Daniel Schaerer

doi:10.1093/mnras/staf903

The AURORA survey: the evolution of multiphase electron densities at high redshift

Michael W. Topping
, Ryan L. Sanders
, Alice E. Shapley
, Anthony J. Pahl
, Naveen A. Reddy
, Daniel P. Stark
, Danielle A. Berg
, Leonardo Clarke
, Fergus Cullen
, James S. Dunlop
, Richard S. Ellis
, N. M.Förster Schreiber
, Garth D. Illingworth
, Tucker Jones
, Desika Narayanan
, Max Pettini
, Daniel Schaerer

Physics And Astronomy

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

We present an analysis of deep JWST/NIRSpec spectra of star-forming galaxies at z ≃ 1.4-10, observed as part of the Assembly of Ultra-deep Rest-optical Observations Revealing Astrophysics (AURORA) survey. We infer median low-ionization electron densities of 268⁺⁴⁵_-49 cm^-3, 350⁺¹⁴⁰_-76 cm^-3, and 480⁺³⁹⁰_-310 cm^-3 at redshifts z= 2.3, z = 3.2, and z = 5.3, respectively, which is best described by an evolutionary trend following (1 + z)^1.5±0.6. We identify weak positive correlations between electron density and star formation rate (SFR) as well as SFR surface density, but no significant trends with stellar mass or specific SFR. Correlations with rest-optical emission line ratios show densities increasing with [Ne III]γ3869/[O II]γ3727 and, potentially, [O III]γ5007/[O II]γ3727, although variations in dust attenuation complicate the latter. Additionally, electron density is more strongly correlated with distance from the local Baldwin, Phillips, and Terlevich (BPT) sequence than can be explained by simple photoionization models. We further derive electron densities from the [C III] doublet probing higher ionization gas, and find a median value of 1.4^+0.7_-0.5 × 10⁴ cm^-3, ∼30 times higher than densities inferred from [S II]. This comparison suggests a consistent H II region structure across cosmic time with dense, high-ionization interiors surrounded by less dense, low-ionization gas. We compare measurements of AURORA galaxies to predictions from the SPHINX galaxy formations, highlighting the interplay between residual molecular cloud pressure in young galaxies and feedback from stellar winds and supernovae as galaxies mature.

Original language	English
Pages (from-to)	1707-1721
Number of pages	15
Journal	Monthly Notices of the Royal Astronomical Society
Volume	541
Issue number	2
DOIs	https://doi.org/10.1093/mnras/staf903
State	Published - Aug 1 2025

Bibliographical note

Publisher Copyright:
© 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.

Funding

We thank the anonymous referee for their helpful comments. This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-03127 for JWST. The specific observations analysed can be accessed via DOI: 10.17909/hvne-7139. We also acknowledge support from NASA grant JWST-GO-01914. TJ acknowledges support from the National Aeronautics and Space Administration (NASA) under grants 80NSSC23K1132 and HSTGO-16697, and from a Chancellor's Fellowship. JSD acknowledges the support of the Royal Society via the award of a Royal Society Research Professorship. We thank the anonymous referee for their helpful comments. This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-03127 for JWST. The specific observations analysed can be accessed via DOI: 10.17909/hvne-7139 . We also acknowledge support from NASA grant JWST-GO-01914. TJ acknowledges support from the National Aeronautics and Space Administration (NASA) under grants 80NSSC23K1132 and HST-GO-16697, and from a Chancellor’s Fellowship. JSD acknowledges the support of the Royal Society via the award of a Royal Society Research Professorship.

Funders	Funder number
Endocrine Society of Australia
Royal Society of Medicine
Canadian Space Agency	JWST-GO-01914
National Aeronautics and Space Administration	80NSSC23K1132, HST-GO-16697

Keywords

galaxies: ISM
galaxies: evolution
galaxies: high-redshift

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1093/mnras/staf903

Cite this

Topping, M. W., Sanders, R. L., Shapley, A. E., Pahl, A. J., Reddy, N. A., Stark, D. P., Berg, D. A., Clarke, L., Cullen, F., Dunlop, J. S., Ellis, R. S., Schreiber, N. M. F., Illingworth, G. D., Jones, T., Narayanan, D., Pettini, M., & Schaerer, D. (2025). The AURORA survey: the evolution of multiphase electron densities at high redshift. Monthly Notices of the Royal Astronomical Society, 541(2), 1707-1721. https://doi.org/10.1093/mnras/staf903

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title = "The AURORA survey: the evolution of multiphase electron densities at high redshift",

abstract = "We present an analysis of deep JWST/NIRSpec spectra of star-forming galaxies at z ≃ 1.4-10, observed as part of the Assembly of Ultra-deep Rest-optical Observations Revealing Astrophysics (AURORA) survey. We infer median low-ionization electron densities of 268+45-49 cm-3, 350+140-76 cm-3, and 480+390-310 cm-3 at redshifts z= 2.3, z = 3.2, and z = 5.3, respectively, which is best described by an evolutionary trend following (1 + z)1.5±0.6. We identify weak positive correlations between electron density and star formation rate (SFR) as well as SFR surface density, but no significant trends with stellar mass or specific SFR. Correlations with rest-optical emission line ratios show densities increasing with [Ne III]γ3869/[O II]γ3727 and, potentially, [O III]γ5007/[O II]γ3727, although variations in dust attenuation complicate the latter. Additionally, electron density is more strongly correlated with distance from the local Baldwin, Phillips, and Terlevich (BPT) sequence than can be explained by simple photoionization models. We further derive electron densities from the [C III] doublet probing higher ionization gas, and find a median value of 1.4+0.7-0.5 × 104 cm-3, ∼30 times higher than densities inferred from [S II]. This comparison suggests a consistent H II region structure across cosmic time with dense, high-ionization interiors surrounded by less dense, low-ionization gas. We compare measurements of AURORA galaxies to predictions from the SPHINX galaxy formations, highlighting the interplay between residual molecular cloud pressure in young galaxies and feedback from stellar winds and supernovae as galaxies mature.",

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author = "Topping, \{Michael W.\} and Sanders, \{Ryan L.\} and Shapley, \{Alice E.\} and Pahl, \{Anthony J.\} and Reddy, \{Naveen A.\} and Stark, \{Daniel P.\} and Berg, \{Danielle A.\} and Leonardo Clarke and Fergus Cullen and Dunlop, \{James S.\} and Ellis, \{Richard S.\} and Schreiber, \{N. M.F{\"o}rster\} and Illingworth, \{Garth D.\} and Tucker Jones and Desika Narayanan and Max Pettini and Daniel Schaerer",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.",

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Topping, MW, Sanders, RL, Shapley, AE, Pahl, AJ, Reddy, NA, Stark, DP, Berg, DA, Clarke, L, Cullen, F, Dunlop, JS, Ellis, RS, Schreiber, NMF, Illingworth, GD, Jones, T, Narayanan, D, Pettini, M & Schaerer, D 2025, 'The AURORA survey: the evolution of multiphase electron densities at high redshift', Monthly Notices of the Royal Astronomical Society, vol. 541, no. 2, pp. 1707-1721. https://doi.org/10.1093/mnras/staf903

TY - JOUR

T1 - The AURORA survey

T2 - the evolution of multiphase electron densities at high redshift

AU - Topping, Michael W.

AU - Sanders, Ryan L.

AU - Shapley, Alice E.

AU - Pahl, Anthony J.

AU - Reddy, Naveen A.

AU - Stark, Daniel P.

AU - Berg, Danielle A.

AU - Clarke, Leonardo

AU - Cullen, Fergus

AU - Dunlop, James S.

AU - Ellis, Richard S.

AU - Schreiber, N. M.Förster

AU - Illingworth, Garth D.

AU - Jones, Tucker

AU - Narayanan, Desika

AU - Pettini, Max

AU - Schaerer, Daniel

PY - 2025/8/1

Y1 - 2025/8/1

N2 - We present an analysis of deep JWST/NIRSpec spectra of star-forming galaxies at z ≃ 1.4-10, observed as part of the Assembly of Ultra-deep Rest-optical Observations Revealing Astrophysics (AURORA) survey. We infer median low-ionization electron densities of 268+45-49 cm-3, 350+140-76 cm-3, and 480+390-310 cm-3 at redshifts z= 2.3, z = 3.2, and z = 5.3, respectively, which is best described by an evolutionary trend following (1 + z)1.5±0.6. We identify weak positive correlations between electron density and star formation rate (SFR) as well as SFR surface density, but no significant trends with stellar mass or specific SFR. Correlations with rest-optical emission line ratios show densities increasing with [Ne III]γ3869/[O II]γ3727 and, potentially, [O III]γ5007/[O II]γ3727, although variations in dust attenuation complicate the latter. Additionally, electron density is more strongly correlated with distance from the local Baldwin, Phillips, and Terlevich (BPT) sequence than can be explained by simple photoionization models. We further derive electron densities from the [C III] doublet probing higher ionization gas, and find a median value of 1.4+0.7-0.5 × 104 cm-3, ∼30 times higher than densities inferred from [S II]. This comparison suggests a consistent H II region structure across cosmic time with dense, high-ionization interiors surrounded by less dense, low-ionization gas. We compare measurements of AURORA galaxies to predictions from the SPHINX galaxy formations, highlighting the interplay between residual molecular cloud pressure in young galaxies and feedback from stellar winds and supernovae as galaxies mature.

AB - We present an analysis of deep JWST/NIRSpec spectra of star-forming galaxies at z ≃ 1.4-10, observed as part of the Assembly of Ultra-deep Rest-optical Observations Revealing Astrophysics (AURORA) survey. We infer median low-ionization electron densities of 268+45-49 cm-3, 350+140-76 cm-3, and 480+390-310 cm-3 at redshifts z= 2.3, z = 3.2, and z = 5.3, respectively, which is best described by an evolutionary trend following (1 + z)1.5±0.6. We identify weak positive correlations between electron density and star formation rate (SFR) as well as SFR surface density, but no significant trends with stellar mass or specific SFR. Correlations with rest-optical emission line ratios show densities increasing with [Ne III]γ3869/[O II]γ3727 and, potentially, [O III]γ5007/[O II]γ3727, although variations in dust attenuation complicate the latter. Additionally, electron density is more strongly correlated with distance from the local Baldwin, Phillips, and Terlevich (BPT) sequence than can be explained by simple photoionization models. We further derive electron densities from the [C III] doublet probing higher ionization gas, and find a median value of 1.4+0.7-0.5 × 104 cm-3, ∼30 times higher than densities inferred from [S II]. This comparison suggests a consistent H II region structure across cosmic time with dense, high-ionization interiors surrounded by less dense, low-ionization gas. We compare measurements of AURORA galaxies to predictions from the SPHINX galaxy formations, highlighting the interplay between residual molecular cloud pressure in young galaxies and feedback from stellar winds and supernovae as galaxies mature.

KW - galaxies: ISM

KW - galaxies: evolution

KW - galaxies: high-redshift

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U2 - 10.1093/mnras/staf903

DO - 10.1093/mnras/staf903

M3 - Article

AN - SCOPUS:105010837418

SN - 0035-8711

VL - 541

SP - 1707

EP - 1721

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

The AURORA survey: the evolution of multiphase electron densities at high redshift

Abstract

Bibliographical note

Funding

Keywords

ASJC Scopus subject areas

Access to Document

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