University of Hertfordshire

From the same journal

From the same journal

By the same authors

  • J.~M. Simpson
  • I. Smail
  • W.-H. Wang
  • D. Riechers
  • J.~S. Dunlop
  • Y. Ao
  • N. Bourne
  • A. Bunker
  • S.~C. Chapman
  • C.-C. Chen
  • H. Dannerbauer
  • T. Goto
  • C.~M. Harrison
  • H.~S. Hwang
  • R.~J. Ivison
  • T. Kodama
  • C.-H. Lee
  • H.-M. Lee
  • M. Lee
  • C.-F. Lim
  • M.~J. Michalowski
  • D.~J. Rosario
  • H. Shim
  • X.~W. Shu
  • A.~M. Swinbank
  • W.-L. Tee
  • Y. Toba
  • E. Valiante
  • J. Wang
  • X.~Z. Zheng
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Original languageEnglish
Article numberL10
Number of pages5
JournalAstrophysical Journal Letters
Publication statusPublished - 19 Jul 2017


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 0farcs4 ± 0farcs1 (~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 ${100}_{-70}^{+15}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$, is undetected in the rest-frame ultraviolet but contributes significantly to the lower angular resolution photometry at rest-frame wavelengths gsim3500 Å. 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.


© 2017. The American Astronomical Society. All rights reserved.

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