1. Reaching for the stars – JWST/NIRSpec spectroscopy of a lensed star candidate at z = 4.76.
- Author
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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, and Conselice, Christopher J
- Subjects
SUPERGIANT stars ,EARLY stars ,STAR clusters ,TEMPERATURE of stars ,STELLAR spectra ,GLOBULAR clusters - Abstract
We present JWST/NIRSpec observations of a highly magnified star candidate at a photometric redshift of z
phot ≃ 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 |$T_{\mathrm{eff,B}}\simeq 15\, 000$| K with either a redder F-type companion (|$T_{\mathrm{eff,F}}\simeq 6\, 250$| 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. [ABSTRACT FROM AUTHOR]- Published
- 2024
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