KMOS3D Reveals Low-level Star Formation Activity in Massive Quiescent Galaxies at 0.7 <z <2.7

Sirio Belli, Reinhard Genzel, Natascha M. Förster Schreiber, Emily Wisnioski, David J. Wilman, Stijn Wuyts, J. Trevor Mendel, Alessandra Beifiori, Ralf Bender, Gabriel B. Brammer, Andreas Burkert, Jeffrey Chan, Rebecca L. Davies, Ric Davies, Maximilian Fabricius, Matteo Fossati, Audrey Galametz, Philipp Lang, Dieter Lutz, Ivelina G. MomchevaErica J. Nelson, Roberto P. Saglia, Linda J. Tacconi, Ken Ichi Tadaki, Hannah Übler, Pieter Van Dokkum

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Abstract

We explore the Hα emission in the massive quiescent galaxies observed by the KMOS3D survey at 0.7 <z <2.7. The Hα line is robustly detected in 20 out of 120 UVJ-selected quiescent galaxies, and we classify the emission mechanism using the Hα line width and the [N ii]/Hα line ratio. We find that AGNs are likely to be responsible for the line emission in more than half of the cases. We also find robust evidence for star formation activity in nine quiescent galaxies, which we explore in detail. The Hα kinematics reveal rotating disks in five of the nine galaxies. The dust-corrected Hα star formation rates are low (0.2-7 M o yr-1), and place these systems significantly below the main sequence. The 24 μm-based, infrared luminosities, instead, overestimate the star formation rates. These galaxies present a lower gas-phase metallicity compared to star-forming objects with similar stellar mass, and many of them have close companions. We therefore conclude that the low-level star formation activity in these nine quiescent galaxies is likely to be fueled by inflowing gas or minor mergers, and could be a sign of rejuvenation events.

Original languageEnglish
Article numberL6
JournalAstrophysical Journal Letters
Volume841
Issue number1
DOIs
Publication statusPublished - 17 May 2017

Keywords

  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: ISM
  • galaxies: star formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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