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

Rosati P.;
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.
2023
Vanzella, E.; Loiacono, F.; Bergamini, P.; Mestriac, U.; Castellano, M.; Rosati, P.; Meneghetti, M.; Grillo, C.; Calura, F.; Mignoli, M.; Bradac, M.; Adamo, A.; Rihtarsic, G.; Dickinson, M.; Gronke, M.; Zanella, A.; Annibali, F.; Willott, C.; Messa, M.; Sani, E.; Acebron, A.; Bolamperti, A.; Comastri, A.; Gilli, R.; Caputi, K. I.; Ricotti, M.; Gruppioni, C.; Ravindranath, S.; Mercurio, A.; Strait, V.; Martis, N.; Pascale, R.; Caminha, G. B.; Annunziatella, M.; Nonino, M.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2532016
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