A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona.

Maude Gull; Daniel R. Weisz; Peter Senchyna; Nathan R. Sandford; Yumi Choi; Anna F. McLeod; Kareem El-Badry; Ylva Götberg; Karoline M. Gilbert; Martha Boyer; Julianne J. Dalcanton; Puragra GuhaThakurta; Steven Goldman; Paola Marigo; Kristen B.W. McQuinn; Giada Pastorelli; Daniel P. Stark; Evan Skillman; Yuan Sen Ting; Benjamin F. Williams

doi:10.3847/1538-4357/aca295

A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona.

Maude Gull
, Daniel R. Weisz
, Peter Senchyna
, Nathan R. Sandford
, Yumi Choi
, Anna F. McLeod
, Kareem El-Badry
, Ylva Götberg
, Karoline M. Gilbert
, Martha Boyer
, Julianne J. Dalcanton
, Puragra GuhaThakurta
, Steven Goldman
, Paola Marigo
, Kristen B.W. McQuinn
, Giada Pastorelli
, Daniel P. Stark
, Evan Skillman
, Yuan Sen Ting
, Benjamin F. Williams

Physics and Astronomy (Twin Cities)

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

17 Scopus citations

Abstract

We characterize massive stars (M > 8 M _⊙) in the nearby (D ∼ 0.8 Mpc) extremely metal-poor (Z ∼ 5% Z _⊙) galaxy Leo A using Hubble Space Telescope ultraviolet (UV), optical, and near-infrared (NIR) imaging along with Keck/Low-Resolution Imaging Spectrograph and MMT/Binospec optical spectroscopy for 18 main-sequence OB stars. We find that: (a) 12 of our 18 stars show emission lines, despite not being associated with an H ii region, suggestive of stellar activity (e.g., mass loss, accretion, binary star interaction), which is consistent with previous predictions of enhanced activity at low metallicity; (b) six are Be stars, which are the first to be spectroscopically studied at such low metallicity—these Be stars have unusual panchromatic SEDs; (c) for stars well fit by the TLUSTY nonlocal thermodynamic equilibrium models, the photometric and spectroscopic values of log ( T eff ) and log ( g ) agree to within ∼0.01 dex and ∼0.18 dex, respectively, indicating that near-UV/optical/NIR imaging can be used to reliably characterize massive (M ∼ 8-30 M _⊙) main-sequence star properties relative to optical spectroscopy; (d) the properties of the most-massive stars in H II regions are consistent with constraints from previous nebular emission line studies; and (e) 13 stars with M > 8M _⊙ are >40 pc from a known star cluster or H II region. Our sample comprises ∼50% of all known massive stars at Z ≲ 10% Z _⊙with derived stellar parameters, high-quality optical spectra, and panchromatic photometry.

Original language	English (US)
Article number	206
Journal	Astrophysical Journal
Volume	941
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/aca295
State	Published - Dec 1 2022

Bibliographical note

Funding Information:
M.G. thanks Miriam Garcia, Chris Evans, Sally Oey, Nate Bastian, Morgan Fouseneau, Dietrich Baade, and the referee for helpful discussions, feedback, and/or comments. M.G. acknowledges support of the “Schweizerische Studienstiftung” and UC Berkeley Cranor Fellowship. Support for this work was provided by NASA through grants GO-15275, GO-15921, GO-16162, GO-16717, AR-15056, AR-16120, and HST-HF2-51457.001-A from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.

Funding Information:
Part 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. Further, this data was made accessible by the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration.

Funding Information:
This work is based on photometric observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

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© 2022. The Author(s). Published by the American Astronomical Society.

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Gull, M., Weisz, D. R., Senchyna, P., Sandford, N. R., Choi, Y., McLeod, A. F., El-Badry, K., Götberg, Y., Gilbert, K. M., Boyer, M., Dalcanton, J. J., GuhaThakurta, P., Goldman, S., Marigo, P., McQuinn, K. B. W., Pastorelli, G., Stark, D. P., Skillman, E., Ting, Y. S., & Williams, B. F. (2022). A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona. Astrophysical Journal, 941(2), Article 206. https://doi.org/10.3847/1538-4357/aca295

A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona. / Gull, Maude; Weisz, Daniel R.; Senchyna, Peter et al.
In: Astrophysical Journal, Vol. 941, No. 2, 206, 01.12.2022.

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

Gull, M, Weisz, DR, Senchyna, P, Sandford, NR, Choi, Y, McLeod, AF, El-Badry, K, Götberg, Y, Gilbert, KM, Boyer, M, Dalcanton, JJ, GuhaThakurta, P, Goldman, S, Marigo, P, McQuinn, KBW, Pastorelli, G, Stark, DP, Skillman, E, Ting, YS & Williams, BF 2022, 'A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona.', Astrophysical Journal, vol. 941, no. 2, 206. https://doi.org/10.3847/1538-4357/aca295

Gull M, Weisz DR, Senchyna P, Sandford NR, Choi Y, McLeod AF et al. A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona. Astrophysical Journal. 2022 Dec 1;941(2):206. doi: 10.3847/1538-4357/aca295

Gull, Maude ; Weisz, Daniel R. ; Senchyna, Peter et al. / A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona. In: Astrophysical Journal. 2022 ; Vol. 941, No. 2.

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title = "A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona.",

abstract = "We characterize massive stars (M > 8 M ⊙) in the nearby (D ∼ 0.8 Mpc) extremely metal-poor (Z ∼ 5\% Z ⊙) galaxy Leo A using Hubble Space Telescope ultraviolet (UV), optical, and near-infrared (NIR) imaging along with Keck/Low-Resolution Imaging Spectrograph and MMT/Binospec optical spectroscopy for 18 main-sequence OB stars. We find that: (a) 12 of our 18 stars show emission lines, despite not being associated with an H ii region, suggestive of stellar activity (e.g., mass loss, accretion, binary star interaction), which is consistent with previous predictions of enhanced activity at low metallicity; (b) six are Be stars, which are the first to be spectroscopically studied at such low metallicity{\textemdash}these Be stars have unusual panchromatic SEDs; (c) for stars well fit by the TLUSTY nonlocal thermodynamic equilibrium models, the photometric and spectroscopic values of log ( T eff ) and log ( g ) agree to within ∼0.01 dex and ∼0.18 dex, respectively, indicating that near-UV/optical/NIR imaging can be used to reliably characterize massive (M ∼ 8-30 M ⊙) main-sequence star properties relative to optical spectroscopy; (d) the properties of the most-massive stars in H II regions are consistent with constraints from previous nebular emission line studies; and (e) 13 stars with M > 8M ⊙ are >40 pc from a known star cluster or H II region. Our sample comprises ∼50\% of all known massive stars at Z ≲ 10\% Z ⊙with derived stellar parameters, high-quality optical spectra, and panchromatic photometry.",

author = "Maude Gull and Weisz, \{Daniel R.\} and Peter Senchyna and Sandford, \{Nathan R.\} and Yumi Choi and McLeod, \{Anna F.\} and Kareem El-Badry and Ylva G{\"o}tberg and Gilbert, \{Karoline M.\} and Martha Boyer and Dalcanton, \{Julianne J.\} and Puragra GuhaThakurta and Steven Goldman and Paola Marigo and McQuinn, \{Kristen B.W.\} and Giada Pastorelli and Stark, \{Daniel P.\} and Evan Skillman and Ting, \{Yuan Sen\} and Williams, \{Benjamin F.\}",

note = "Funding Information: M.G. thanks Miriam Garcia, Chris Evans, Sally Oey, Nate Bastian, Morgan Fouseneau, Dietrich Baade, and the referee for helpful discussions, feedback, and/or comments. M.G. acknowledges support of the {\textquotedblleft}Schweizerische Studienstiftung{\textquotedblright} and UC Berkeley Cranor Fellowship. Support for this work was provided by NASA through grants GO-15275, GO-15921, GO-16162, GO-16717, AR-15056, AR-16120, and HST-HF2-51457.001-A from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Funding Information: Part 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. Further, this data was made accessible by the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. Funding Information: This work is based on photometric observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Publisher Copyright: {\textcopyright} 2022. The Author(s). Published by the American Astronomical Society.",

year = "2022",

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doi = "10.3847/1538-4357/aca295",

language = "English (US)",

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T1 - A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona.

AU - Gull, Maude

AU - Weisz, Daniel R.

AU - Senchyna, Peter

AU - Sandford, Nathan R.

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AU - McLeod, Anna F.

AU - El-Badry, Kareem

AU - Götberg, Ylva

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AU - Goldman, Steven

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AU - Stark, Daniel P.

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AU - Ting, Yuan Sen

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N1 - Funding Information: M.G. thanks Miriam Garcia, Chris Evans, Sally Oey, Nate Bastian, Morgan Fouseneau, Dietrich Baade, and the referee for helpful discussions, feedback, and/or comments. M.G. acknowledges support of the “Schweizerische Studienstiftung” and UC Berkeley Cranor Fellowship. Support for this work was provided by NASA through grants GO-15275, GO-15921, GO-16162, GO-16717, AR-15056, AR-16120, and HST-HF2-51457.001-A from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Funding Information: Part 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. Further, this data was made accessible by the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. Funding Information: This work is based on photometric observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society.

PY - 2022/12/1

Y1 - 2022/12/1

N2 - We characterize massive stars (M > 8 M ⊙) in the nearby (D ∼ 0.8 Mpc) extremely metal-poor (Z ∼ 5% Z ⊙) galaxy Leo A using Hubble Space Telescope ultraviolet (UV), optical, and near-infrared (NIR) imaging along with Keck/Low-Resolution Imaging Spectrograph and MMT/Binospec optical spectroscopy for 18 main-sequence OB stars. We find that: (a) 12 of our 18 stars show emission lines, despite not being associated with an H ii region, suggestive of stellar activity (e.g., mass loss, accretion, binary star interaction), which is consistent with previous predictions of enhanced activity at low metallicity; (b) six are Be stars, which are the first to be spectroscopically studied at such low metallicity—these Be stars have unusual panchromatic SEDs; (c) for stars well fit by the TLUSTY nonlocal thermodynamic equilibrium models, the photometric and spectroscopic values of log ( T eff ) and log ( g ) agree to within ∼0.01 dex and ∼0.18 dex, respectively, indicating that near-UV/optical/NIR imaging can be used to reliably characterize massive (M ∼ 8-30 M ⊙) main-sequence star properties relative to optical spectroscopy; (d) the properties of the most-massive stars in H II regions are consistent with constraints from previous nebular emission line studies; and (e) 13 stars with M > 8M ⊙ are >40 pc from a known star cluster or H II region. Our sample comprises ∼50% of all known massive stars at Z ≲ 10% Z ⊙with derived stellar parameters, high-quality optical spectra, and panchromatic photometry.

AB - We characterize massive stars (M > 8 M ⊙) in the nearby (D ∼ 0.8 Mpc) extremely metal-poor (Z ∼ 5% Z ⊙) galaxy Leo A using Hubble Space Telescope ultraviolet (UV), optical, and near-infrared (NIR) imaging along with Keck/Low-Resolution Imaging Spectrograph and MMT/Binospec optical spectroscopy for 18 main-sequence OB stars. We find that: (a) 12 of our 18 stars show emission lines, despite not being associated with an H ii region, suggestive of stellar activity (e.g., mass loss, accretion, binary star interaction), which is consistent with previous predictions of enhanced activity at low metallicity; (b) six are Be stars, which are the first to be spectroscopically studied at such low metallicity—these Be stars have unusual panchromatic SEDs; (c) for stars well fit by the TLUSTY nonlocal thermodynamic equilibrium models, the photometric and spectroscopic values of log ( T eff ) and log ( g ) agree to within ∼0.01 dex and ∼0.18 dex, respectively, indicating that near-UV/optical/NIR imaging can be used to reliably characterize massive (M ∼ 8-30 M ⊙) main-sequence star properties relative to optical spectroscopy; (d) the properties of the most-massive stars in H II regions are consistent with constraints from previous nebular emission line studies; and (e) 13 stars with M > 8M ⊙ are >40 pc from a known star cluster or H II region. Our sample comprises ∼50% of all known massive stars at Z ≲ 10% Z ⊙with derived stellar parameters, high-quality optical spectra, and panchromatic photometry.

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A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A* * This paper includes data gathered with the 10 m Keck Telescopes located at W. M. Keck Observatory, Hawaii and with the 6.5 m Multiple Mirror Telescope (MMT) located at Mt. Hopkins, Arizona.

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