Reaching for the stars – JWST/NIRSpec spectroscopy of a lensed star candidate at z = 4.76

Furtak, Lukas J; Meena, Ashish K; Zackrisson, Erik; Zitrin, Adi; Brammer, Gabriel B; Coe, Dan; Diego, José M; Eldridge, Jan J; Jiménez-Teja, Yolanda; Kokorev, Vasily; Ricotti, Massimo; Welch, Brian; Windhorst, Rogier A; Abdurro’uf; Andrade-Santos, Felipe; Bhatawdekar, Rachana; Bradley, Larry D; Broadhurst, Tom; Chen, Wenlei; Conselice, Christopher J; Dayal, Pratika; Frye, Brenda L; Fujimoto, Seiji; Y-Y Hsiao, Tiger; Kelly, Patrick L; Mahler, Guillaume; Mandelker, Nir; Norman, Colin; Oguri, Masamune; Pirzkal, Norbert; Postman, Marc; Ravindranath, Swara; Vanzella, Eros; Wilkins, Stephen M

Abstract

We present JWST/NIRSpec observations of a highly magnified star candidate at a photometric redshift of zphot ≃ 4.8, previously detected in JWST/NIRCam imaging of the strong lensing (SL) cluster MACS J0647+7015 (z = 0.591). The spectroscopic observation allows us to precisely measure the redshift of the host arc at zspec = 4.758 ± 0.004, and the star’s spectrum displays clear Lyman- and Balmer-breaks commensurate with this redshift. A fit to the spectrum suggests a B-type super-giant star of surface temperature
 K with either a redder F-type companion (⁠
 K) or significant dust attenuation (AV ≃ 0.82) along the line of sight. We also investigate the possibility that this object is a magnified young globular cluster rather than a single star. We show that the spectrum is in principle consistent with a star cluster, which could also accommodate the lack of flux variability between the two epochs. However, the lack of a counter image and the strong upper limit on the size of the object from lensing symmetry, r ≲ 0.5 pc, could indicate that this scenario is somewhat less likely – albeit not completely ruled out by the current data. The presented spectrum seen at a time when the Universe was only ∼1.2 Gyr old showcases the ability of JWST to study early stars through extreme lensing.

Citation

Furtak, L. J., Meena, A. K., Zackrisson, E., Zitrin, A., Brammer, G. B., Coe, D., …Wilkins, S. M. (2024). Reaching for the stars – JWST/NIRSpec spectroscopy of a lensed star candidate at z = 4.76. Monthly Notices of the Royal Astronomical Society: Letters, 527(1), L7–L13. https://doi.org/10.1093/mnrasl/slad135

• Journal Article Type: Article
• Acceptance Date: Sep 20, 2023
• Online Publication Date: Sep 22, 2023
• Publication Date: 2024-01
• Deposit Date: Feb 6, 2024
• Publicly Available Date: Feb 6, 2024
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 527
• Issue: 1
• Pages: L7–L13
• DOI: https://doi.org/10.1093/mnrasl/slad135
• Public URL: https://durham-repository.worktribe.com/output/2227840