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arXiv · 1709.02809

An extreme proto-cluster of luminous dusty starbursts in the early Universe

I. Oteo·R. J. Ivison·L. Dunne·A. Manilla-Robles·S. Maddox·A. J. R. Lewis·G. de Zotti·M. Bremer·D. L. Clements·A. Cooray·H. Dannerbauer·S. Eales·J. Greenslade·A. Omont·I. Perez-Fournón·D. Riechers·D. Scott·P. van der Werf·A. Weiss·Z-Y. Zhang
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Abstract

We report the identification of an extreme proto-cluster of galaxies in the early Universe whose core (nicknamed Distant Red Core, DRC) is formed by at least ten dusty star-forming galaxies (DSFGs), confirmed to lie at $z_{\rm spec} = 4.002$ via detection of [CI](1-0), $^{12}$CO(6-5), $^{12}$CO(4-3), $^{12}$CO(2-1) and ${\rm H_2O} (2_{11} - 2_{02})$ emission lines, detected using ALMA and ATCA. The spectroscopically-confirmed components of the proto-cluster are distributed over a ${\rm 260\, kpc \times 310\, kpc}$ region and have a collective obscured star-formation rate (SFR) of $\sim 6500 \, M_\odot \, {\rm yr}^{-1}$, considerably higher than has been seen before in any proto-cluster of galaxies or over-densities of DSFGs at $z \gtrsim 4$. Most of the star formation is taking place in luminous DSFGs since no Ly$α$ emitters are detected in the proto-cluster core, apart from a Ly$α$ blob located next to one of the DRC dusty components and extending over $60\,{\rm kpc}$. The total obscured SFR of the proto-cluster could rise to ${\rm SFR} \sim 14,400 \, M_\odot \, {\rm yr}^{-1}$ if all the members of an over-density of bright DSFGs discovered around DRC in a wide-field LABOCA 870-$μ$m image are part of the same structure. The total halo mass of DRC could be as high as $\sim 4.4 \times 10^{13}\,M_\odot$ and could be the progenitor of a Coma-like cluster at $z = 0$. The relatively short gas-depletion times of the DRC components suggest either the presence of a mechanism able to trigger extreme star formation simultaneously in galaxies spread over a few hundred kpc or the presence of gas flows from the cosmic web able to sustain star formation over several hundred million years.

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I. Oteo, R. J. Ivison, L. Dunne, A. Manilla-Robles, S. Maddox, A. J. R. Lewis, G. de Zotti, M. Bremer, D. L. Clements, A. Cooray, H. Dannerbauer, S. Eales, J. Greenslade, A. Omont, I. Perez-Fournón, D. Riechers, D. Scott, P. van der Werf, A. Weiss, Z-Y. Zhang. 2017-09-20. An extreme proto-cluster of luminous dusty starbursts in the early Universe. https://doi.org/10.3847/1538-4357%2Faaa1f1

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