Abstract
Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 (WC IV,0 ≳ 20 Å) are uniformly stronger than observed locally (WC IV,0 ≲ 2 Å), likely due to the relatively high metallicities (Z/Z☉ > 0.1) typically probed by UV surveys of nearby galaxies. We present new HST/COS spectra of six nearby (z < 0.01) extremely metal-poor galaxies (XMPs, Z/Z☉ ≲ 0.1) targeted to address this limitation and provide constraints on the highly uncertain ionizing spectra powered by low-metallicity massive stars. Our data reveal a range of spectral features, including one of the most prominent nebular C IV doublets yet observed in local star-forming systems and strong He II emission. Using all published UV observations of local XMPs to date, we find that nebular C IV emission is ubiquitous in very high specific star formation rate systems at low metallicity, but still find equivalent widths smaller than those measured in individual lensed systems at z > 6. Our moderate-resolution HST/COS data allow us to conduct an analysis of the stellar winds in a local nebular C IV emitter, which suggests that some of the tension with z > 6 data may be due to existing local samples not yet probing sufficiently high α/Fe abundance ratios. Our results indicate that C IV emission can play a crucial role in the JWST and ELT era by acting as an accessible signpost of very low metallicity (Z/Z☉ < 0.1) massive stars in assembling reionization-era systems.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3492-3506 |
| Number of pages | 15 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 488 |
| Issue number | 3 |
| DOIs | |
| State | Published - Sep 21 2019 |
Keywords
- Galaxies: evolution
- Galaxies: stellar content
- Stars: massive
- Ultraviolet: galaxies
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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Extremely metal-poor galaxies with HST/COS : Laboratories for models of low-metallicity massive stars and high-redshift galaxies. / Senchyna, Peter; Stark, Daniel P.; Chevallard, Jacopo; Charlot, Stéphane; Jones, Tucker; Vidal-García, Alba.
In: Monthly Notices of the Royal Astronomical Society, Vol. 488, No. 3, 21.09.2019, p. 3492-3506.Research output: Contribution to journal › Article › peer-review
}
TY - JOUR
T1 - Extremely metal-poor galaxies with HST/COS
T2 - Laboratories for models of low-metallicity massive stars and high-redshift galaxies
AU - Senchyna, Peter
AU - Stark, Daniel P.
AU - Chevallard, Jacopo
AU - Charlot, Stéphane
AU - Jones, Tucker
AU - Vidal-García, Alba
N1 - Funding Information: DPS acknowledges support from the National Science Foundation through the grant AST-1410155. JC, SC, and AVG acknowledge support from the European Research Council (ERC) via an Advanced Grant under grant agreement no. 321323-NEOGAL. AVG also acknowledges support from the ERC via an Advanced Grant under grant agreement no. 742719-MIST. Funding Information: This project used public archival data from the Dark Energy Survey (DES). Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology FacilitiesCouncil of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundac¸ão Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovac¸ão, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones En-ergéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l’Espai (IEEC/CSIC), the Institut de Física d’Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the OzDES Membership Consortium, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University. Funding Information: The authors thank the anonymous referee for their helpful report. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. Support for program #14679 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. Some of the data presented herein were 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This project used public archival data from the Dark Energy Survey (DES). Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology FacilitiesCouncil of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Funda??o Carlos Chagas Filho de Amparo ? Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico and the Minist?rio da Ci?ncia, Tecnologia e Inova??o, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energ?ticas, Medioambientales y Tecnol?gicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgen?ssische Technische Hochschule (ETH) Z?rich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ci?ncies de l?Espai (IEEC/CSIC), the Institut de F?sica d?Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universit?t M?nchen and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the OzDES Membership Consortium, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University. Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. DPS acknowledges support from the National Science Foundation through the grant AST-1410155. JC, SC, and AVG acknowledge support from the European Research Council (ERC) via an Advanced Grant under grant agreement no. 321323-NEOGAL. AVG also acknowledges support from the ERC via an Advanced Grant under grant agreement no. 742719-MIST. This research used ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013), MATPLOTLIB (Hunter 2007), NUMPY and SCIPY (Jones et al. 2001), the SIMBAD data base, operated at CDS, Strasbourg, France; NASA?s Astrophysics Data System; and services or data provided by the NOAO Data Lab (NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation). Funding Information: The authors thank the anonymous referee for their helpful report. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. Support for program #14679 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. Some of the data presented herein were 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 the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Publisher Copyright: © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
PY - 2019/9/21
Y1 - 2019/9/21
N2 - Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 (WC IV,0 ≳ 20 Å) are uniformly stronger than observed locally (WC IV,0 ≲ 2 Å), likely due to the relatively high metallicities (Z/Z☉ > 0.1) typically probed by UV surveys of nearby galaxies. We present new HST/COS spectra of six nearby (z < 0.01) extremely metal-poor galaxies (XMPs, Z/Z☉ ≲ 0.1) targeted to address this limitation and provide constraints on the highly uncertain ionizing spectra powered by low-metallicity massive stars. Our data reveal a range of spectral features, including one of the most prominent nebular C IV doublets yet observed in local star-forming systems and strong He II emission. Using all published UV observations of local XMPs to date, we find that nebular C IV emission is ubiquitous in very high specific star formation rate systems at low metallicity, but still find equivalent widths smaller than those measured in individual lensed systems at z > 6. Our moderate-resolution HST/COS data allow us to conduct an analysis of the stellar winds in a local nebular C IV emitter, which suggests that some of the tension with z > 6 data may be due to existing local samples not yet probing sufficiently high α/Fe abundance ratios. Our results indicate that C IV emission can play a crucial role in the JWST and ELT era by acting as an accessible signpost of very low metallicity (Z/Z☉ < 0.1) massive stars in assembling reionization-era systems.
AB - Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 (WC IV,0 ≳ 20 Å) are uniformly stronger than observed locally (WC IV,0 ≲ 2 Å), likely due to the relatively high metallicities (Z/Z☉ > 0.1) typically probed by UV surveys of nearby galaxies. We present new HST/COS spectra of six nearby (z < 0.01) extremely metal-poor galaxies (XMPs, Z/Z☉ ≲ 0.1) targeted to address this limitation and provide constraints on the highly uncertain ionizing spectra powered by low-metallicity massive stars. Our data reveal a range of spectral features, including one of the most prominent nebular C IV doublets yet observed in local star-forming systems and strong He II emission. Using all published UV observations of local XMPs to date, we find that nebular C IV emission is ubiquitous in very high specific star formation rate systems at low metallicity, but still find equivalent widths smaller than those measured in individual lensed systems at z > 6. Our moderate-resolution HST/COS data allow us to conduct an analysis of the stellar winds in a local nebular C IV emitter, which suggests that some of the tension with z > 6 data may be due to existing local samples not yet probing sufficiently high α/Fe abundance ratios. Our results indicate that C IV emission can play a crucial role in the JWST and ELT era by acting as an accessible signpost of very low metallicity (Z/Z☉ < 0.1) massive stars in assembling reionization-era systems.
KW - Galaxies: evolution
KW - Galaxies: stellar content
KW - Stars: massive
KW - Ultraviolet: galaxies
UR - http://www.scopus.com/inward/record.url?scp=85075252169&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85075252169&partnerID=8YFLogxK
U2 - 10.1093/mnras/stz1907
DO - 10.1093/mnras/stz1907
M3 - Article
AN - SCOPUS:85075252169
VL - 488
SP - 3492
EP - 3506
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 3
ER -