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This is the final published version of an article that has been published in its final definitive form by Institute of Physics Publishing, 2017.
For re-use rights please refer to the publisher's terms and conditions.
© 2017. The American Astronomical Society. All rights reserved. The identification of high-redshift, massive galaxies with old stellar populations may pose challenges to some models of galaxy formation. However, to securely classify a galaxy as quiescent, it is necessary to exclude significant ongoing star formation, something that can be challenging to achieve at high redshifts. In this Letter, we analyze deep ALMA/870 μm and SCUBA-2/450 μm imaging of the claimed "post-starburst" galaxy ZF 20115 at z = 3.717 that exhibits a strong Balmer break and absorption lines. The rest-frame far-infrared imaging identifies a luminous starburst 0.″4 0.″1 (∼3 kpc in projection) from the position of the ultraviolet/optical emission and is consistent with lying at the redshift of ZF 20115. The star-forming component, with an obscured star formation rate of 100+15 -70M⊙ yr-1, is undetected in the rest-frame ultraviolet but contributes significantly to the lower angular resolution photometry at rest-frame wavelengths 3500. This contribution from the obscured starburst, especially in the Spitzer/IRAC wavebands, significantly complicates the determination of a reliable stellar mass for the ZF 20015 system, and we conclude that this source does not pose a challenge to current models of galaxy formation. The multi-wavelength observations of ZF 20115 unveil a complex system with an intricate and spatially varying star formation history. ZF 20115 demonstrates that understanding high-redshift obscured starbursts will only be possible with multi-wavelength studies that include high-resolution observations, available with the James Webb Space Telescope, at mid-infrared wavelengths.
Author(s): Simpson JM, Smail I, Wang W-H, Riechers D, Dunlop JS, Ao Y, Bourne N, Bunker A, Chapman SC, Chen C-C, Dannerbauer H, Geach JE, Goto T, Harrison CM, Hwang HS, Ivison RJ, Kodama T, Lee C-H, Lee H-M, Lee M, Lim C-F, Michalowski MJ, Rosario DJ, Shim H, Shu XW, Swinbank AM, Tee W-L, Toba Y, Valiante E, Wang J, Zheng XZ
Publication type: Article
Publication status: Published
Journal: Astrophysical Journal Letters
Year: 2017
Volume: 844
Issue: 1
Online publication date: 19/07/2017
Acceptance date: 15/06/2017
Date deposited: 05/02/2020
ISSN (print): 2041-8205
ISSN (electronic): 2041-8213
Publisher: Institute of Physics Publishing
URL: https://doi.org/10.3847/2041-8213/aa7cf2
DOI: 10.3847/2041-8213/aa7cf2
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