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http://hdl.handle.net/20.500.12386/26559
Titolo: | Paving the way for the JWST: witnessing globular cluster formation at z > 3 | Autori: | VANZELLA, Eros CALURA, Francesco MENEGHETTI, MASSIMO MERCURIO, AMATA CASTELLANO, MARCO Caminha, G. B. Balestra, I. Rosati, P. TOZZI, Paolo De Barros, S. GRAZIAN, Andrea D'Ercole, A. Ciotti, L. Caputi, K. Grillo, C. MERLIN, Emiliano PENTERICCI, Laura FONTANA, Adriano CRISTIANI, Stefano Coe, D. |
Data pubblicazione: | 2017 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 467 | Fascicolo: | 4 | Da pagina:: | 4304 | Abstract: | We report on five compact, extremely young (<10 Myr) and blue (β<SUB>UV</SUB> < -2.5, F<SUB>λ</SUB> = λ<SUP>β</SUP>) 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 (R<SUB>e</SUB>) are between 16 and 140 pc, the stellar masses are ≃1-20 × 10<SUP>6</SUP> M<SUB>☉</SUB>, the magnitudes are m<SUB>UV</SUB> = 28.8-31.4 (-17 < M<SUB>UV</SUB> < -15) and specific star formation rates can be as large as ∼800 Gyr<SUP>-1</SUP>. 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 σ<SUB>v</SUB> ≃ 20 km s<SUP>-1</SUP>, implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with delensed M<SUB>UV</SUB> ≃ -15.3 (m<SUB>UV</SUB> ≃ 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 m<SUB>UV</SUB> ≃ 32, a stellar mass of 0.5 × 10<SUP>6</SUP> M<SUB>☉</SUB> and a star formation rate of 0.06 M<SUB>☉</SUB> yr<SUP>-1</SUP> 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. | URI: | http://hdl.handle.net/20.500.12386/26559 | URL: | http://arxiv.org/abs/1612.01526v2 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stx351 | Bibcode ADS: | 2017MNRAS.467.4304V | Fulltext: | open |
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