In Search of the First Stars: An Ultra-compact and Very-low-metallicity Lyα Emitter Deep within the Epoch of Reionization

Chris J. Willott; Yoshihisa Asada; Kartheik G. Iyer; Jon Judež; Gregor Rihtaršič; Nicholas S. Martis; Ghassan T. E. Sarrouh; Guillaume Desprez; Anishya Harshan; Lamiya Mowla; Gaël Noirot; Giordano Felicioni; Maruša Bradač; Gabe Brammer; Adam Muzzin; Marcin Sawicki; Jacqueline Antwi-Danso; Vladan Markov; Roberta Tripodi

doi:10.3847/1538-4357/addf49

The Astrophysical Journal (Jan 2025)

In Search of the First Stars: An Ultra-compact and Very-low-metallicity Lyα Emitter Deep within the Epoch of Reionization

Chris J. Willott,
Yoshihisa Asada,
Kartheik G. Iyer,
Jon Judež,
Gregor Rihtaršič,
Nicholas S. Martis,
Ghassan T. E. Sarrouh,
Guillaume Desprez,
Anishya Harshan,
Lamiya Mowla,
Gaël Noirot,
Giordano Felicioni,
Maruša Bradač,
Gabe Brammer,
Adam Muzzin,
Marcin Sawicki,
Jacqueline Antwi-Danso,
Vladan Markov,
Roberta Tripodi

Affiliations

Chris J. Willott: ORCiD; NRC Herzberg , 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada ; [email protected]
Yoshihisa Asada: ORCiD; Department of Astronomy and Physics and Institute for Computational Astrophysics, Saint Mary’s University , 923 Robie Street, Halifax, NS B3H 3C3, Canada; Department of Astronomy, Kyoto University , Sakyo-ku, Kyoto 606-8502, Japan
Kartheik G. Iyer: ORCiD; Columbia Astrophysics Laboratory, Columbia University , 550 West 120th Street, New York, NY 10027, USA
Jon Judež: Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
Gregor Rihtaršič: ORCiD; Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
Nicholas S. Martis: ORCiD; Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
Ghassan T. E. Sarrouh: ORCiD; Department of Physics and Astronomy, York University , 4700 Keele St. Toronto, ON M3J 1P3, Canada
Guillaume Desprez: ORCiD; Kapteyn Astronomical Institute, University of Groningen , P.O. Box 800, 9700AV Groningen, The Netherlands
Anishya Harshan: ORCiD; Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
Lamiya Mowla: ORCiD; Whitin Observatory, Department of Physics and Astronomy, Wellesley College , 106 Central Street, Wellesley, MA 02481, USA
Gaël Noirot: Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
Giordano Felicioni: Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
Maruša Bradač: ORCiD; Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia; Department of Physics and Astronomy, University of California Davis , 1 Shields Avenue, Davis, CA 95616, USA
Gabe Brammer: ORCiD; Cosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen N, Denmark
Adam Muzzin: ORCiD; Department of Physics and Astronomy, York University , 4700 Keele St. Toronto, ON M3J 1P3, Canada
Marcin Sawicki: ORCiD; Department of Astronomy and Physics and Institute for Computational Astrophysics, Saint Mary’s University , 923 Robie Street, Halifax, NS B3H 3C3, Canada
Jacqueline Antwi-Danso: ORCiD; David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4, Canada
Vladan Markov: ORCiD; Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia
Roberta Tripodi: ORCiD; Department of Mathematics and Physics, University of Ljubljana , Jadranska ulica 19, SI-1000 Ljubljana, Slovenia; INAF—Osservatorio Astronomico di Roma , Via Frascati 33, Monte Porzio Catone, 00078, Italy

DOI: https://doi.org/10.3847/1538-4357/addf49
Journal volume & issue: Vol. 988, no. 1
p. 26

Abstract

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We present JWST observations of a gravitationally lensed, extremely metal-poor galaxy at redshift z = 8.203 ± 0.001 from the CANUCS survey. Based on the low oxygen to Balmer line ratios, we infer a gas-phase metallicity of 12 + log(O/H) = 6.85 (1.4% solar), making CANUCS-A370-z8-LAE one of the most metal-poor galaxies known at z > 7. The galaxy has a high H β equivalent width of 225 ± 50 Å, small half-light radius of only ${r}_{\mathrm{hl}}=3{8}_{-19}^{+3}$ pc, and high star formation rate density of 50–100 M _⊙ yr ^−1 kpc ^−2 . The galaxy shows high-equivalent-width Ly α emission with an inferred Ly α escape fraction of 0.21 ± 0.05. The high escape fraction of Ly α is likely due to the compact starbursting nature of the galaxy combined with its location in an overdensity traced by at least two other galaxies spectroscopically confirmed to lie within δz = 0.01 that have helped to reionize the environment. The low metallicity of CANUCS-A370-z8-LAE is best explained by a model where infalling metal-poor gas dilutes the interstellar medium, rather than being a young galaxy forming its first stellar populations.

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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