The MOSDEF survey: Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5

Ryan L. Sanders; Alice E. Shapley; Naveen A. Reddy; Mariska Kriek; Brian Siana; Alison L. Coil; Bahram Mobasher; Irene Shivaei; William R. Freeman; Mojegan Azadi; Sedona H. Price; Gene Leung; Tara Fetherolf; Laura de Groot; Tom Zick; Francesca M. Fornasini; Guillermo Barro

doi:10.1093/mnras/stz3032

The MOSDEF survey: Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5

Ryan L. Sanders, Alice E. Shapley, Naveen A. Reddy, Mariska Kriek, Brian Siana, Alison L. Coil, Bahram Mobasher, Irene Shivaei, William R. Freeman, Mojegan Azadi, Sedona H. Price, Gene Leung, Tara Fetherolf, Laura de Groot, Tom Zick, Francesca M. Fornasini, Guillermo Barro

Physics And Astronomy

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94 Scopus citations

Abstract

We present detections of [O III] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7-3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M_∗/M☉) = 7-10. We find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass-metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Direct-method O/H evolves by ≲0.1 dex at fixed M_∗ and star formation rate from z ∼ 0 to 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with supersolar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar O/Fe at high redshift caused by rapid formation time-scales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼10¹⁰ M☉ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.

Original language	English
Pages (from-to)	1427-1455
Number of pages	29
Journal	Monthly Notices of the Royal Astronomical Society
Volume	491
Issue number	1
DOIs	https://doi.org/10.1093/mnras/stz3032
State	Published - Jan 1 2020

Bibliographical note

Funding Information:
Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation. We acknowledge support from NSF AAG grants AST-1312780, 1312547, 1312764, and 1313171, archival grant AR-13907 provided by NASA through the Space Telescope Science Institute, and grant NNX16AF54G from the NASA ADAP program. We also acknowledge a NASA contract supporting the ‘WFIRST Extragalactic Potential Observations (EXPO) Science Investigation Team’ (15-WFIRST15-0004), administered by GSFC. We additionally acknowledge the 3D-HST collaboration for providing spectroscopic and photometric catalogues used in the MOSDEF survey. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, the work presented herein would not have been possible.

Publisher Copyright:
© 2019 The Author(s)

Keywords

Galaxies: abundances
Galaxies: high-redshift

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/mnras/stz3032

Cite this

Sanders, R. L., Shapley, A. E., Reddy, N. A., Kriek, M., Siana, B., Coil, A. L., Mobasher, B., Shivaei, I., Freeman, W. R., Azadi, M., Price, S. H., Leung, G., Fetherolf, T., de Groot, L., Zick, T., Fornasini, F. M., & Barro, G. (2020). The MOSDEF survey: Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5. Monthly Notices of the Royal Astronomical Society, 491(1), 1427-1455. https://doi.org/10.1093/mnras/stz3032

@article{b14c72d6ae8b42758b35e5f748817bfc,

title = "The MOSDEF survey: Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5",

abstract = "We present detections of [O III] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7-3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M∗/M☉) = 7-10. We find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass-metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Direct-method O/H evolves by ≲0.1 dex at fixed M∗ and star formation rate from z ∼ 0 to 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with supersolar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar O/Fe at high redshift caused by rapid formation time-scales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼1010 M☉ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.",

keywords = "Galaxies: abundances, Galaxies: high-redshift",

author = "Sanders, {Ryan L.} and Shapley, {Alice E.} and Reddy, {Naveen A.} and Mariska Kriek and Brian Siana and Coil, {Alison L.} and Bahram Mobasher and Irene Shivaei and Freeman, {William R.} and Mojegan Azadi and Price, {Sedona H.} and Gene Leung and Tara Fetherolf and {de Groot}, Laura and Tom Zick and Fornasini, {Francesca M.} and Guillermo Barro",

note = "Funding Information: Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation. We acknowledge support from NSF AAG grants AST-1312780, 1312547, 1312764, and 1313171, archival grant AR-13907 provided by NASA through the Space Telescope Science Institute, and grant NNX16AF54G from the NASA ADAP program. We also acknowledge a NASA contract supporting the {\textquoteleft}WFIRST Extragalactic Potential Observations (EXPO) Science Investigation Team{\textquoteright} (15-WFIRST15-0004), administered by GSFC. We additionally acknowledge the 3D-HST collaboration for providing spectroscopic and photometric catalogues used in the MOSDEF survey. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, the work presented herein would not have been possible. Publisher Copyright: {\textcopyright} 2019 The Author(s)",

year = "2020",

month = jan,

day = "1",

doi = "10.1093/mnras/stz3032",

language = "English",

volume = "491",

pages = "1427--1455",

number = "1",

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Sanders, RL, Shapley, AE, Reddy, NA, Kriek, M, Siana, B, Coil, AL, Mobasher, B, Shivaei, I, Freeman, WR, Azadi, M, Price, SH, Leung, G, Fetherolf, T, de Groot, L, Zick, T, Fornasini, FM & Barro, G 2020, 'The MOSDEF survey: Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5', Monthly Notices of the Royal Astronomical Society, vol. 491, no. 1, pp. 1427-1455. https://doi.org/10.1093/mnras/stz3032

TY - JOUR

T1 - The MOSDEF survey

T2 - Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5

AU - Sanders, Ryan L.

AU - Shapley, Alice E.

AU - Reddy, Naveen A.

AU - Kriek, Mariska

AU - Siana, Brian

AU - Coil, Alison L.

AU - Mobasher, Bahram

AU - Shivaei, Irene

AU - Freeman, William R.

AU - Azadi, Mojegan

AU - Price, Sedona H.

AU - Leung, Gene

AU - Fetherolf, Tara

AU - de Groot, Laura

AU - Zick, Tom

AU - Fornasini, Francesca M.

AU - Barro, Guillermo

N1 - Funding Information: Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation. We acknowledge support from NSF AAG grants AST-1312780, 1312547, 1312764, and 1313171, archival grant AR-13907 provided by NASA through the Space Telescope Science Institute, and grant NNX16AF54G from the NASA ADAP program. We also acknowledge a NASA contract supporting the ‘WFIRST Extragalactic Potential Observations (EXPO) Science Investigation Team’ (15-WFIRST15-0004), administered by GSFC. We additionally acknowledge the 3D-HST collaboration for providing spectroscopic and photometric catalogues used in the MOSDEF survey. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, the work presented herein would not have been possible. Publisher Copyright: © 2019 The Author(s)

PY - 2020/1/1

Y1 - 2020/1/1

N2 - We present detections of [O III] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7-3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M∗/M☉) = 7-10. We find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass-metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Direct-method O/H evolves by ≲0.1 dex at fixed M∗ and star formation rate from z ∼ 0 to 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with supersolar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar O/Fe at high redshift caused by rapid formation time-scales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼1010 M☉ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.

AB - We present detections of [O III] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7-3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M∗/M☉) = 7-10. We find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass-metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Direct-method O/H evolves by ≲0.1 dex at fixed M∗ and star formation rate from z ∼ 0 to 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with supersolar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar O/Fe at high redshift caused by rapid formation time-scales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼1010 M☉ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.

KW - Galaxies: abundances

KW - Galaxies: high-redshift

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The MOSDEF survey: Direct-method metallicities and ISM conditions at z ∼ 1.5-3.5

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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