ATTENZIONE!!! IL SISTEMA E' UTILIZZABILE ESCLUSIVAMENTE IN MODALITA' "CONSULTAZIONE". CAUSA PROBLEMI TECNICI, SI PREGA DI NON EFFETTUARE L'AUTENTICAZIONE, FINO A NUOVA COMUNICAZIONE. GRAZIE
 

Paving the way for the JWST: witnessing globular cluster formation at z > 3

Journal
Date Issued
2017
Author(s)
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Caminha, G. B.
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Balestra, I.
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Rosati, P.
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De Barros, S.
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D'Ercole, A.
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Ciotti, L.
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Caputi, K.
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Grillo, C.
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Coe, D.
DOI
Abstract
We report on five compact, extremely young (<10 Myr) and blue (βUV < -2.5, Fλ = λβ) objects observed with VLT/Multi Unit Spectroscopic Explorer at redshifts 3.1169 and 3.235, in addition to three objects at z = 6.145. These sources are strongly magnified (3-40 times) by the Hubble Frontier Field galaxy clusters MACS J0416 and AS1063. Their delensed half-light radii (Re) are between 16 and 140 pc, the stellar masses are ≃1-20 × 106 M☉, the magnitudes are mUV = 28.8-31.4 (-17 < MUV < -15) and specific star formation rates can be as large as ∼800 Gyr-1. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-GCs discovered so far. Rest-frame optical high-dispersion spectroscopy of one of them at z = 3.1169 yields a velocity dispersion σv ≃ 20 km s-1, implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with delensed MUV ≃ -15.3 (mUV ≃ 31.4), shows a stellar mass and a star formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z = 6.145, with delensed mUV ≃ 32, a stellar mass of 0.5 × 106 M☉ and a star formation rate of 0.06 M☉ yr-1 is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z > 3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the Universe and augment Lyα visibility during reionization. This work underlines the crucial role of JWST in characterizing the rest-frame optical and near-infrared properties of such low-luminosity high-z objects.
Volume
467
Issue
4
Start page
4304
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.467.4304V
Rights
open.access
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