Year: 2024
Type: article
Abstract: We report the serendipitous discovery of a faint (MUV > −12.2), low-metallicity (Z ∼ 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 Hβ, [O III]λλ4959, 5007, and Hα emissions are detected, with equivalent widths exceeding 200 Å, 800 Å, and 1300 Å (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 λrest ∼ 2000 Å and ∼5000 Å, respectively), suggesting a stellar mass lower than a few 104 M⊙ under an instantaneous burst scenario. The inferred ionizing photon production efficiency (ξion) is high: ξion ≳ 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 H II region potentially powered by currently undetected, extremely efficient, low-metallicity star complexes or clusters. We propose that massive O-type stars populate these low-mass, low-metallicity, high-redshift satellites, likely observed in an early and short formation phase, and contribute to the ionization of the surrounding medium.
Authors: E. Vanzella, F. Loiacono, M. Messa, M. Castellano, P. Bergamini, A. Zanella, F. Annibali, B. Sun, M. Dickinson, A. Adamo, F. Calura, M. Ricotti, P. Rosati, M. Meneghetti, C. Grillo, M. Bradač, C. J. Conselice, H. Yan, A. Bolamperti, U. Meštrić, R. Gilli, M. Gronke, C. Willott, E. Sani, A. Acebron, A. Comastri, M. Mignoli, C. Gruppioni, A. Mercurio, V. Strait, R. Pascale, M. Annunziatella, B. L. Frye, L. D. Bradley, N. A. Grogin, A. M. Koekemoer, S. Ravindranath, J. C. J. D’Silva, J. Summers, G. Rihtaršič, R. Windhorst
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Smithsonian Institution, National Aeronautics and Space Administration, European Commission, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Ministero dell’Istruzione, dell’Università e della Ricerca, Nuclear Safety and Security Commission, Max-Planck-Gesellschaft, Javna Agencija za Raziskovalno Dejavnost RS, Vetenskapsrådet, Goddard Space Flight Center, Smithsonian Astrophysical Observatory
Awards: G1055883707, G112473895, G112949879, Exploring Cosmic Dawn with James Webb Space Telescope, G490430286, NEXT GENERATION FRONTIER STUDIES OF GALAXY FORMATI ON AND EVOLUTION WITH NEXT GENERATION SPACE TELES, G6608474652, G6722835988, THE PROPOSAL SEEKS TO ACCOMPLISH SEVERAL INVESTIGATIONS TO SIMULATE THE PERFORMANCE OF JWST DEEP FIELD SURVEYS, VARYING AS-YET-POORLY CHARACTERIZED P, Zooming into Dark Matter and proto-galaxies with massive lensing clusters, G785121043, Star formation within evolving galaxies: the revolution of the James Webb Space Telescope, IN 2002 WE WERE GRANTED 110 HOURS GTO TIME FOR A JWST MEDIUM-DEEP SURVEY. WITH HST AND SPITZER EXPERIENCE 14 YEARS LATER WE REDEFINE THIS SURVEY TO IMAGE~18 NIRCAM FIELDS IN 7 FILTERS TO AB<~ 29 29.3 MAG YIELDING 140 000 GALAXIES AT 0<~ Z<~ 12 15 IN 0.05 DEG2 (>~ 30 HUDFS!). WE WILL STUDY GALAXY ASSEMBLY + SUPER-MASSIVE BLACK-HOLE GROWTH AT Z 0 7 INCLUDING OBJECT VARIABILITY ON MONTHS YEARS TIMESCALES. WE STUDY THE REIONIZING POPULATION AT Z 2 8 AND USE THE BEST LENSING TARGETS TO OPTIMIZE OUR STUDY OF FIRST LIGHT OBJECTS AT Z 10 15. OUR SCIENCE GOALS ARE: 1. GALAXY ASSEMBLY; 2. SUPER-MASSIVE BLACK-HOLE GROWTH; 3. REIONIZATION; 4. FIRST LIGHT; 5. STUDY THE BEST LENSING CLUSTERS TO FIND JWST OBJECTS. MAP&REMOVE STRAYLIGHT GRADIENTS AND QUANTIFY SAMPLE COMPLETENESS IN RANDOM FIELD&CLUSTER IMAGES: WE WILL: A) USE HUDF AND HFF DATA TO SIMULATE MAP AND REMOVE A RANGE OF STRAYLIGHT AMPLITUDES AND GRADIENTS THAT COULD AFFECT RANDOM DEEP FIELDS (DFS) AND CLUSTER FIELDS WITH JWST; B) DETERMINE ACCURATE COMPLETENESS CORRECTIONS VS. GALAXY FLUX SIZE WAVELENGTH AND LOCATION IN JWST DFS OF VARIOUS DEPTH AND IN CLUSTER FIELDS WITH THEIR KNOWN GALAXY CLUSTER+ICL FOREGROUND; C) DETERMINE THE CLUSTER SELECTION FUNCTIONS BY FOLDING LENSING MAPS WITH SIMULATED BACKGROUND IMAGES YIELDING SIMULATED LENSED IMAGES AND THEIR COMPLETENESS CORRECTIONS FOR LENSED SOURCES WHICH WE SHOW CAN BE FACTORS 2 3; AND D) MODEL COSMIC VARIANCE IN HIERARCHICAL MODELS AT Z 6 15. WE WILL CORRECT THE LFS FOR THESE COMPLETENESS FUNCTIONS. WE WILL THEN USE A BAYESIAN CODE TO DETERMINE THE OPTIMAL SET OF LF EVOLUTION PARAMETERS FROM THE AVAILABLE JWST DATA TO QUANTIFY HOW GALAXIES ASSEMBLED SINCE Z<~ 15., G972786147
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