TY - JOUR
T1 - Extreme ionizing properties of a metal-poor, M≈- 12 star complex in the first gigayear
AU - Vanzella, E.
AU - Loiacono, F.
AU - Messa, M.
AU - Castellano, M.
AU - Bergamini, P.
AU - Zanella, A.
AU - Annibali, F.
AU - Sun, B.
AU - Dickinson, M.
AU - Adamo, A.
AU - Calura, F.
AU - Ricotti, M.
AU - Rosati, P.
AU - Meneghetti, M.
AU - Grillo, C.
AU - Bradač, M.
AU - Conselice, C. J.
AU - Yan, H.
AU - Bolamperti, A.
AU - Meštriä, U.
AU - Gilli, R.
AU - Gronke, M.
AU - Willott, C.
AU - Sani, E.
AU - Acebron, A.
AU - Comastri, A.
AU - Mignoli, M.
AU - Gruppioni, C.
AU - Mercurio, A.
AU - Strait, V.
AU - Pascale, R.
AU - Annunziatella, M.
AU - Frye, B. L.
AU - Bradley, L. D.
AU - Grogin, N. A.
AU - Koekemoer, A. M.
AU - Ravindranath, S.
AU - D-Silva, J. C.J.
AU - Summers, J.
AU - Rihtaršič, G.
AU - Windhorst, R.
N1 - Publisher Copyright:
© The Authors 2024.
PY - 2024/11/1
Y1 - 2024/11/1
N2 - We report the serendipitous discovery of a faint (MUV > -12:2), low-metallicity (_Azip ∼0.02 Z) ionizing source, dubbed T2c, with a spectroscopic redshift of z = 6.146. T2c is part of a larger structure amplified by the Hubble Frontier Field galaxy cluster MACSJ0416 and was observed with the James Webb Space Telescope (JWST) NIRSpec integral field unit. Stacking the short-wavelength NIRCam data reveals no stellar continuum detection down to a magnitude limit of mUV ' 31:0 (3σ). However, prominent H [Oiii λ λ λ4959; 5007, and Hemissions are detected, with equivalent widths exceeding 200 Å, 800 Å, and 1300Å (3σ), respectively. The corresponding intrinsic (magnification-corrected ×23±3) ultraviolet and optical rest-frame magnitudes exceed 34.4 and 33.9 (corresponding to MUV and Mopt fainter than -12.2 and -12.8 at rest2000Å and ∼5000 Å, respectively), suggesting a stellar mass lower than a few 104 M under an instantaneous burst scenario. The inferred ionizing photon production effciency (ζion) is high: ζion & 26:08(25:86) 3(5)σ, assuming no dust attenuation and no Lyman continuum leakage. This indicates the presence of massive stars despite the low mass of the object. The very poor sampling of the initial mass function in such a low-mass star-forming complex suggests that the formation of very massive stars might be favored in very low-metallicity environments. T2c is surrounded by Balmer and weak oxygen emission on a spatial scale of a few hundred parsecs, after correcting for lensing effects. This system resembles a Hii region potentially powered by currently undetected, extremely effcient, low-metallicity star complexes or clusters.
AB - We report the serendipitous discovery of a faint (MUV > -12:2), low-metallicity (_Azip ∼0.02 Z) ionizing source, dubbed T2c, with a spectroscopic redshift of z = 6.146. T2c is part of a larger structure amplified by the Hubble Frontier Field galaxy cluster MACSJ0416 and was observed with the James Webb Space Telescope (JWST) NIRSpec integral field unit. Stacking the short-wavelength NIRCam data reveals no stellar continuum detection down to a magnitude limit of mUV ' 31:0 (3σ). However, prominent H [Oiii λ λ λ4959; 5007, and Hemissions are detected, with equivalent widths exceeding 200 Å, 800 Å, and 1300Å (3σ), respectively. The corresponding intrinsic (magnification-corrected ×23±3) ultraviolet and optical rest-frame magnitudes exceed 34.4 and 33.9 (corresponding to MUV and Mopt fainter than -12.2 and -12.8 at rest2000Å and ∼5000 Å, respectively), suggesting a stellar mass lower than a few 104 M under an instantaneous burst scenario. The inferred ionizing photon production effciency (ζion) is high: ζion & 26:08(25:86) 3(5)σ, assuming no dust attenuation and no Lyman continuum leakage. This indicates the presence of massive stars despite the low mass of the object. The very poor sampling of the initial mass function in such a low-mass star-forming complex suggests that the formation of very massive stars might be favored in very low-metallicity environments. T2c is surrounded by Balmer and weak oxygen emission on a spatial scale of a few hundred parsecs, after correcting for lensing effects. This system resembles a Hii region potentially powered by currently undetected, extremely effcient, low-metallicity star complexes or clusters.
KW - Galaxies: high-redshift
KW - Galaxies: star clusters: general
KW - Galaxies: star formation
KW - Gravitational lensing: strong
KW - HII regions
UR - http://www.scopus.com/inward/record.url?scp=85210299732&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202451696
DO - 10.1051/0004-6361/202451696
M3 - Article
AN - SCOPUS:85210299732
SN - 0004-6361
VL - 691
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A251
ER -