Confirming the Quiescent Galaxy Population out to $z=3$: A Stacking   Analysis of Mid-, Far-Infrared and Radio Data
  We present stringent constraints on the average mid-, far-infrared and radio emissions of $\sim$14200 quiescent galaxies (QGs), identified out to $z=3$ in the COSMOS field via their rest-frame NUV$-$r and r$-$J colors, and with stellar masses $M_{\star}=10^{9.8-12.2} \,M_{\odot} $. Stacking in deep Spitzer (MIPS $24\,\mu$m), Herschel (PACS and SPIRE), and VLA (1.4 GHz) maps reveals extremely low dust-obscured star formation rates for QGs (SFR $<0.1-3\,M_{\odot}$yr$^{-1}$ at $z \leqslant 2$ and $<6-18\,M_{\odot}$yr$^{-1}$ at $z > 2$), consistent with the low unobscured SFRs ($<0.01-1.2\,M_{\odot}$yr$^{-1}$) inferred from modeling their ultraviolet-to-near-infrared photometry. The average SFRs of QGs are $>10\times$ below those of star-forming galaxies (SFGs) within the $M_{\star}$- and $z$-ranges considered. The stacked 1.4 GHz signals (S/N $> 5$) are, if attributed solely to star formation, in excess of the total (obscured plus unobscured) SFR limits, suggestive of a widespread presence of low-luminosity active galactic nuclei (AGN) among QGs. Our results reaffirm the existence of a significant population QGs out to $z = 3$, thus corroborating the need for powerful quenching mechanism(s) to terminate star formation in galaxies at earlier epochs. 
Allison W. S. Man, Thomas R. Greve, Sune Toft, Benjamin Magnelli,   Alexander Karim, Olivier Ilbert, Mara Salvato, Emeric Le...
astro-ph.GA astro-ph.CO