We present JWST/Near Infrared Spectrograph (NIRSpec) integral field spectroscopy (IFS) of a lensed Population III candidate stellar complex (dubbed Lensed And Pristine 1, LAP1), with a lensing-corrected stellar mass of -104 M· and an absolute luminosity of MUV > 11.2 (mUV > 35.6), confirmed at redshift 6.639 ± 0.004. The system is strongly amplified (μ 100) by straddling a critical line of the Hubble Frontier Field galaxy cluster MACS J0416. Although the stellar continuum is currently not detected in the Hubble and JWST/Near Infrared Camera (NIRCam) and Near Infrared Imager and Slitless Spectrograph (NIRISS) imaging, arclet-like shapes of Lyman and Balmer lines, Lyα, Hγ, Hβ and Hα are detected with NIRSpec IFS with signal-to-noise ratios (S/N) of approximately 5 13 and large equivalent widths (> 300 2000 ), along with a remarkably weak [O III]λλ4959, 5007 at S/N 4. LAP1 shows a large ionizing photon production efficiency, log(ξion[erg Hz1]) > 26. From the metallicity indexes R23 = ([O ¯III] + [O ¯II])/Hβ 0.74 and R3 = ([O ¯III]/Hβ) = 0.55 ± 0.14, we derive an oxygen abundance of 12 + log(O/H) 6.3. Intriguingly, the Hα emission is also measured in mirrored subcomponents where no [O ¯III] is detected, providing even more stringent upper limits on the metallicity if in situ star formation is ongoing in this region (12 + log(O/H) < 6). The formal stellar mass limit of the subcomponents would correspond to 103 M· or MUV fainter than 10. Alternatively, this metal-free, pure line-emitting region could be the first case of a fluorescing H ¯I gas region induced by transverse escaping ionizing radiation from a nearby star complex. The presence of large equivalent-width hydrogen lines and the deficiency of metal lines in such a small region make LAP1 the most metal-poor star-forming region currently known in the reionization era and a promising site that may host isolated, pristine stars.

An extremely metal-poor star complex in the reionization era: Approaching Population III stars with JWST / E. Vanzella, F. Loiacono, P. Bergamini, U. Mestric, M. Castellano, P. Rosati, M. Meneghetti, C. Grillo, F. Calura, M. Mignoli, M. Bradac, A. Adamo, G. Rihtarsic, M. Dickinson, M. Gronke, A. Zanella, F. Annibali, C. Willott, M. Messa, E. Sani, A. Acebron Munoz, A. Bolamperti, A. Comastri, R. Gilli, K.I. Caputi, M. Ricotti, C. Gruppioni, S. Ravindranath, A. Mercurio, V. Strait, N. Martis, R. Pascale, G.B. Caminha, M. Annunziatella, M. Nonino. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 1432-0746. - 678:(2023 Oct 18), pp. A173.1-A173.15. [10.1051/0004-6361/202346981]

An extremely metal-poor star complex in the reionization era: Approaching Population III stars with JWST

P. Bergamini;U. Mestric;C. Grillo;A. Acebron Munoz;
2023

Abstract

We present JWST/Near Infrared Spectrograph (NIRSpec) integral field spectroscopy (IFS) of a lensed Population III candidate stellar complex (dubbed Lensed And Pristine 1, LAP1), with a lensing-corrected stellar mass of -104 M· and an absolute luminosity of MUV > 11.2 (mUV > 35.6), confirmed at redshift 6.639 ± 0.004. The system is strongly amplified (μ 100) by straddling a critical line of the Hubble Frontier Field galaxy cluster MACS J0416. Although the stellar continuum is currently not detected in the Hubble and JWST/Near Infrared Camera (NIRCam) and Near Infrared Imager and Slitless Spectrograph (NIRISS) imaging, arclet-like shapes of Lyman and Balmer lines, Lyα, Hγ, Hβ and Hα are detected with NIRSpec IFS with signal-to-noise ratios (S/N) of approximately 5 13 and large equivalent widths (> 300 2000 ), along with a remarkably weak [O III]λλ4959, 5007 at S/N 4. LAP1 shows a large ionizing photon production efficiency, log(ξion[erg Hz1]) > 26. From the metallicity indexes R23 = ([O ¯III] + [O ¯II])/Hβ 0.74 and R3 = ([O ¯III]/Hβ) = 0.55 ± 0.14, we derive an oxygen abundance of 12 + log(O/H) 6.3. Intriguingly, the Hα emission is also measured in mirrored subcomponents where no [O ¯III] is detected, providing even more stringent upper limits on the metallicity if in situ star formation is ongoing in this region (12 + log(O/H) < 6). The formal stellar mass limit of the subcomponents would correspond to 103 M· or MUV fainter than 10. Alternatively, this metal-free, pure line-emitting region could be the first case of a fluorescing H ¯I gas region induced by transverse escaping ionizing radiation from a nearby star complex. The presence of large equivalent-width hydrogen lines and the deficiency of metal lines in such a small region make LAP1 the most metal-poor star-forming region currently known in the reionization era and a promising site that may host isolated, pristine stars.
Galaxies: high-redshift; Galaxies: star formation; Gravitational lensing: strong; Stars: Population III;
Settore FIS/05 - Astronomia e Astrofisica
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   MINISTERO DELL'ISTRUZIONE E DEL MERITO
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   MINISTERO DELL'ISTRUZIONE E DEL MERITO
   2020SKSTHZ_001
18-ott-2023
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/1019978
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