An Imperfectly Passive Nature: Bright Submillimeter Emission from Dust-obscured Star Formation in the z = 3.717 “Passive” System, ZF 20115

Simpson, J.M.; Smail, Ian; Wang, Wei-Hao; Riechers, D.; Dunlop, J.S.; Ao, Y.; Bourne, N.; Bunker, A.; Chapman, S.C.; Chen, Chian-Chou; Dannerbauer, H.; Geach, J.E.; Goto, T.; Harrison, C.M.; Hwang, H.S.; Ivison, R.J.; Kodama, Tadayuki; Lee, C.-H.; Lee, H.-M.; Lee, M.; Lim, C.-F.; Michałowski, M.J.; Rosario, D.J.; Shim, H.; Shu, X.W.; Swinbank, A.M.; Tee, W.-L.; Toba, Y.; Valiante, E.; Wang, Junxian; Zheng, X.Z.

doi:10.3847/2041-8213/aa7cf2

An Imperfectly Passive Nature: Bright Submillimeter Emission from Dust-obscured Star Formation in the z = 3.717 “Passive” System, ZF 20115

Simpson, J.M.; Smail, Ian; Wang, Wei-Hao; Riechers, D.; Dunlop, J.S.; Ao, Y.; Bourne, N.; Bunker, A.; Chapman, S.C.; Chen, Chian-Chou; Dannerbauer, H.; Geach, J.E.; Goto, T.; Harrison, C.M.; Hwang, H.S.; Ivison, R.J.; Kodama, Tadayuki; Lee, C.-H.; Lee, H.-M.; Lee, M.; Lim, C.-F.; Michałowski, M.J.; Rosario, D.J.; Shim, H.; Shu, X.W.; Swinbank, A.M.; Tee, W.-L.; Toba, Y.; Valiante, E.; Wang, Junxian; Zheng, X.Z.

Authors

J.M. Simpson

Professor Ian Smail ian.smail@durham.ac.uk
Emeritus Professor

Wei-Hao Wang

D. Riechers

J.S. Dunlop

Y. Ao

N. Bourne

A. Bunker

S.C. Chapman

Chian-Chou Chen

H. Dannerbauer

J.E. Geach

T. Goto

C.M. Harrison

H.S. Hwang

R.J. Ivison

Tadayuki Kodama

C.-H. Lee

H.-M. Lee

M. Lee

C.-F. Lim

M.J. Michałowski

D.J. Rosario

H. Shim

X.W. Shu

A.M. Swinbank

W.-L. Tee

Y. Toba

E. Valiante

Junxian Wang

X.Z. Zheng

Abstract

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.

Citation

Simpson, J., Smail, I., Wang, W., Riechers, D., Dunlop, J., Ao, Y., …Zheng, X. (2017). An Imperfectly Passive Nature: Bright Submillimeter Emission from Dust-obscured Star Formation in the z = 3.717 “Passive” System, ZF 20115. Astrophysical Journal Letters, 844(1), Article L10. https://doi.org/10.3847/2041-8213/aa7cf2

Journal Article Type	Article
Acceptance Date	Jun 15, 2017
Online Publication Date	Jul 19, 2017
Publication Date	Jul 19, 2017
Deposit Date	Aug 18, 2017
Publicly Available Date	Aug 18, 2017
Journal	Astrophysical Journal Letters
Print ISSN	2041-8205
Electronic ISSN	2041-8213
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	844
Issue	1
Article Number	L10
DOI	https://doi.org/10.3847/2041-8213/aa7cf2