TY - JOUR
T1 - Early Results from GLASS-JWST. VII. Evidence for Lensed, Gravitationally Bound Protoglobular Clusters at z = 4 in the Hubble Frontier Field A2744* * Based on observations collected with JWST under the ERS program 1324 (PI T. Treu).
AU - Vanzella, E.
AU - Castellano, M.
AU - Bergamini, P.
AU - Treu, T.
AU - Mercurio, A.
AU - Scarlata, C.
AU - Rosati, P.
AU - Grillo, C.
AU - Acebron, A.
AU - Caminha, G. B.
AU - Nonino, M.
AU - Nanayakkara, T.
AU - Roberts-Borsani, G.
AU - Bradac, M.
AU - Wang, X.
AU - Brammer, G.
AU - Strait, V.
AU - Vulcani, B.
AU - Meštrić, U.
AU - Meneghetti, M.
AU - Calura, F.
AU - Henry, Alaina
AU - Zanella, A.
AU - Trenti, M.
AU - Boyett, K.
AU - Morishita, T.
AU - Calabrò, A.
AU - Glazebrook, K.
AU - Marchesini, D.
AU - Birrer, S.
AU - Yang, L.
AU - Jones, T.
N1 - Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/12/1
Y1 - 2022/12/1
N2 - We investigate the blue and optical rest-frame sizes (λ ≃ 2300-4000 Å) of three compact star-forming regions in a galaxy at z = 4 strongly lensed (×30, ×45, and ×100) by the Hubble Frontier Field galaxy cluster A2744 using GLASS-ERS James Webb Space Telescope (JWST)/NIRISS imaging at 1.15 μm, 1.50 μm, and 2.0 μm with a point-spread function ≲0.″1. In particular, the Balmer break is probed in detail for all multiply imaged sources of the system. With ages of a few tens of Myr, stellar masses in the range (0.7-4.0) ×106 M ⊙ and optical/ultraviolet effective radii spanning the interval 3 < R eff < 20 pc, such objects are currently the highest-redshift (spectroscopically confirmed) gravitationally bound young massive star clusters (YMCs), with stellar mass surface densities resembling those of local globular clusters. Optical (4000 Å, JWST-based) and ultraviolet (1600 Å, Hubble Space Telescope-based) sizes are fully compatible. The contribution to the ultraviolet underlying continuum emission (1600 Å) is ∼30%, which decreases by a factor of 2 in the optical for two of the YMCs (∼4000 Å rest-frame), reflecting the young ages (<30 Myr) inferred from the spectral energy distribution fitting and supported by the presence of high-ionization lines secured with the Very Large Telescope/MUSE. Such bursty forming regions enhance the specific star formation rate of the galaxy, which is ≃10 Gyr−1. This galaxy would be among the extreme analogs observed in the local universe having a high star formation rate surface density and a high occurrence of massive stellar clusters in formation.
AB - We investigate the blue and optical rest-frame sizes (λ ≃ 2300-4000 Å) of three compact star-forming regions in a galaxy at z = 4 strongly lensed (×30, ×45, and ×100) by the Hubble Frontier Field galaxy cluster A2744 using GLASS-ERS James Webb Space Telescope (JWST)/NIRISS imaging at 1.15 μm, 1.50 μm, and 2.0 μm with a point-spread function ≲0.″1. In particular, the Balmer break is probed in detail for all multiply imaged sources of the system. With ages of a few tens of Myr, stellar masses in the range (0.7-4.0) ×106 M ⊙ and optical/ultraviolet effective radii spanning the interval 3 < R eff < 20 pc, such objects are currently the highest-redshift (spectroscopically confirmed) gravitationally bound young massive star clusters (YMCs), with stellar mass surface densities resembling those of local globular clusters. Optical (4000 Å, JWST-based) and ultraviolet (1600 Å, Hubble Space Telescope-based) sizes are fully compatible. The contribution to the ultraviolet underlying continuum emission (1600 Å) is ∼30%, which decreases by a factor of 2 in the optical for two of the YMCs (∼4000 Å rest-frame), reflecting the young ages (<30 Myr) inferred from the spectral energy distribution fitting and supported by the presence of high-ionization lines secured with the Very Large Telescope/MUSE. Such bursty forming regions enhance the specific star formation rate of the galaxy, which is ≃10 Gyr−1. This galaxy would be among the extreme analogs observed in the local universe having a high star formation rate surface density and a high occurrence of massive stellar clusters in formation.
UR - http://www.scopus.com/inward/record.url?scp=85143876777&partnerID=8YFLogxK
U2 - 10.3847/2041-8213/ac8c2d
DO - 10.3847/2041-8213/ac8c2d
M3 - Article
AN - SCOPUS:85143876777
SN - 2041-8205
VL - 940
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L53
ER -