Witnessing the birth of the red sequence: ALMA high-resolution imaging of [CII] and dust in two interacting ultra-red starbursts at z = 4.425

I. Oteo, R. J. Ivison, L. Dunne, I. Smail, M. Swinbank, Z-Y Zhang, A Lewis, S. Maddox, D. Riechers, S. Serjeant, P. Van der Werf, A.D. Biggs, M. Bremer, P. Cigan, Dave L. Clements, A. Cooray, H. Dannerbauer, S. Eales, E. Ibar, H. MessiasM. J. Michałowski, I. Pérez-Fournon, E. van Kampen

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Abstract

Exploiting the sensitivity and spatial resolution of the Atacama Large Millimeter/submillimeter Array, we have studied the morphology and the physical scale of the interstellar medium—both gas and dust—in SGP 38326, an unlensed pair of interacting starbursts at z = 4.425. SGP 38326 is the most luminous star bursting system known at z > 4, with a total IR luminosity of LIR ∼ 2.5 × 1013 L and a star formation rate of ∼ 4500 M yr−1 . SGP 38326 also contains a molecular gas reservoir among the most massive yet found in the early universe, and it is the likely progenitor of a massive, red-and-dead elliptical galaxy at z ∼ 3. Probing scales of ∼0″.1 or ∼800 pc we find that the smooth distribution of the continuum emission from cool dust grains contrasts with the more irregular morphology of the gas, as traced by the [C II] fine structure emission. The gas is also extended over larger physical scales than the dust. The velocity information provided by the resolved [C II] emission reveals that the dynamics of the two interacting components of SGP 38326 are each compatible with disk-like, ordered rotation, but also reveals an ISM which is turbulent and unstable. Our observations support a scenario where at least a subset of the most distant extreme starbursts are highly dissipative mergers of gas-rich galaxies.
Original languageEnglish
Number of pages11
JournalAstrophysical Journal
Volume827
Issue number1
DOIs
Publication statusPublished - 4 Aug 2016

Keywords

  • Astrophysics - Astrophysics of Galaxies

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