Magnifying the Early Episodes of Star Formation: Super Star Clusters at Cosmological Distances

被引：73

作者：

Vanzella, E. ^{[1
]}

Castellano, M. ^{[2
]}

Meneghetti, M. ^{[1
]}

Mercurio, A. ^{[3
]}

Caminha, G. B. ^{[1
,4
]}

Cupani, G. ^{[5
]}

Calura, F. ^{[1
]}

Christensen, L. ^{[6
]}

Merlin, E. ^{[2
]}

Rosati, P. ^{[4
]}

Gronke, M. ^{[7
]}

Dijkstra, M. ^{[7
]}

Mignoli, M. ^{[1
]}

Gilli, R. ^{[1
]}

De Barros, S. ^{[8
]}

Caputi, K. ^{[9
]}

Grillo, C. ^{[6
,10
]}

Balestra, I. ^{[11
]}

Cristiani, S. ^{[5
]}

Nonino, M. ^{[5
]}

Giallongo, E. ^{[2
]}

Grazian, A. ^{[2
]}

Pentericci, L. ^{[2
]}

Fontana, A. ^{[2
]}

Comastri, A. ^{[2
]}

Vignali, C. ^{[2
,12
]}

Zamorani, G. ^{[2
]}

Brusa, M. ^{[2
,12
]}

Bergamini, P. ^{[13
]}

Tozzi, P. ^{[14
]}

机构：

[1] INAF, Osservatorio Astron Bologna, Via Gobetti 93-3, I-40129 Bologna, Italy

[2] INAF, Osservatorio Astron Roma, Via Frascati 33, I-00040 Monte Porzio Catone, Italy

[3] INAF, Osservatorio Astron Capodimonte, Via Moiariello 16, I-80131 Naples, Italy

[4] Univ Ferrara, Dipartimento Fis & Sci Terra, Via Saragat 1, I-44122 Ferrara, Italy

[5] INAF, Osservatorio Astron Trieste, Via GB Tiepolo 11, I-34131 Trieste, Italy

[6] Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark

[7] Univ Oslo, Inst Theoret Astrophys, Postboks 1029 Blindern, NO-0315 Oslo, Norway

[8] Univ Geneva, Observ Geneva, 51 Ch Maillettes, CH-1290 Chavannes Des Bois, Switzerland

[9] Univ Groningen, Kapteyn Astron Inst, Postbus 800, NL-9700 AV Groningen, Netherlands

[10] Univ Milan, Dipartimento Fis, Via Celoria 16, I-20133 Milan, Italy

[11] Univ Observ Munich, Scheinerstr 1, D-819 Munich, Germany

[12] Univ Bologna, Dipartimento Fis & Astron, Via Gobetti 93-2, I-40129 Bologna, Italy

[13] Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy

[14] INAF, Osservatorio Astrofis Arcetri, Largo E Fermi, I-50125 Florence, Italy

来源：

ASTROPHYSICAL JOURNAL | 2017年 / 842卷 / 01期

基金：

欧洲研究理事会;

关键词：

cosmology: observations; galaxies: formation; galaxies: high-redshift; LY-ALPHA EMISSION; SIMILAR-TO; 2-3; INTERSTELLAR-MEDIUM; IONIZING-RADIATION; FORMING GALAXIES; FAINT GALAXIES; LINE RATIOS; GAS; METALLICITY; REIONIZATION;

D O I：

10.3847/1538-4357/aa74ae

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We study the spectrophotometric properties of a highly magnified (mu similar or equal to 40-70) pair of stellar systems identified at z = 3.2222 behind the Hubble Frontier Field galaxy cluster MACS J0416. Five multiple images (out of six) have been spectroscopically confirmed by means of VLT/MUSE and VLT/X-Shooter observations. Each image includes two faint (m(UV) similar or equal to 30.6), young (less than or similar to 100 Myr), low-mass (< 10(7) M-circle dot), low-metallicity (12 + Log(O/H) similar or equal to 7.7, or 1/10 solar), and compact (30 pc effective radius) stellar systems separated by similar or equal to 300 pc after correcting for lensing amplification. We measured several rest-frame ultraviolet and optical narrow (sigma(nu) less than or similar to 25 km s(-1)) high-ionization lines. These features may be the signature of very hot (T > 50,000 K) stars within dense stellar clusters, whose dynamical mass is likely dominated by the stellar component. Remarkably, the ultraviolet metal lines are not accompanied by Ly alpha emission (e.g., C IV/Ly alpha > 15), despite the fact that the Ly alpha line flux is expected to be 150 times brighter (inferred from the H beta flux). A spatially offset, strongly magnified (mu > 50) Ly alpha emission with a spatial extent less than or similar to 7.6 kpc(2) is instead identified 2 kpc away from the system. The origin of such a faint emission could be the result of fluorescent Ly alpha induced by a transverse leakage of ionizing radiation emerging from the stellar systems and/or may be associated with an underlying and barely detected object (with m(UV) > 34 de-lensed). This is the first confirmed metal-line emitter at such low-luminosity and redshift without Ly alpha emission-suggesting that, at least in some cases, a non-uniform covering factor of the neutral gas might hamper the Ly alpha detection.

引用

页数：10

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