We report on a superdense star-forming region with an effective radius (Re) smaller than 13 pc identified at z = 6.143 and showing a star formation rate density ΣSFR ∼ 1000M⊙ yr-1 kpc-2 (or conservatively >300 M⊙ yr-1 kpc-2). Such a dense region is detected with S/N ≳ 40 hosted by a dwarf extending over 440 pc, dubbed D1. D1 is magnified by a factor 17.4(±5.0) behind the Hubble Frontier Field galaxy cluster MACS J0416 and elongated tangentially by a factor 13.2 ± 4.0 (including the systematic errors). The lens model accurately reproduces the positions of the confirmed multiple images with a rms of 0.35 arcsec. D1 is part of an interacting star-forming complex extending over 800 pc. The SED-fitting, the very blue ultraviolet slope (β ≃ -2.5, Fλ ∼ λβ), and the prominent Lyα emission of the stellar complex imply that very young (<10-100 Myr), moderately dust-attenuated (E(B - V) < 0.15) stellar populations are present and organized in dense subcomponents. We argue that D1 (with a stellar mass of 2 × 107 M⊙) might contain a young massive star cluster of M ≲ 106 M⊙ and MUV ≃ -15.6 (or mUV = 31.1), confined within a region of 13 pc, and not dissimilar from some local super star clusters (SSCs). The ultraviolet appearance of D1 is also consistent with a simulated local dwarf hosting an SSC placed at z = 6 and lensed back to the observer. This compact system fits into some popular globular cluster formation scenarios. We show that future high spatial resolution imaging (e.g. E-ELT/MAORY-MICADO and VLT/MAVIS) will allow us to spatially resolve light profiles of 2-8 pc.
Massive star cluster formation under the microscope at z = 6 / E. Vanzella, F. Calura, M. Meneghetti, M. Castellano, G.B. Caminha, A. Mercurio, G. Cupani, P. Rosati, C. Grillo, R. Gilli, M. Mignoli, G. Fiorentino, C. Arcidiacono, M. Lombini, F. Cortecchia. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 483:3(2019 Mar), pp. 3618-3635.
|Titolo:||Massive star cluster formation under the microscope at z = 6|
|Parole Chiave:||Galaxies: formation; Galaxies: starburst; Gravitational lensing: strong|
|Settore Scientifico Disciplinare:||Settore FIS/05 - Astronomia e Astrofisica|
|Data di pubblicazione:||mar-2019|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1093/mnras/sty3311|
|Appare nelle tipologie:||01 - Articolo su periodico|