In and out star formation in z ~ 1.5 quiescent galaxies from rest-frame UV spectroscopy and the far-infrared

R. Gobat, E. Daddi, V. Strazzullo, B. Garilli, M. Mignoli, Z. Ma, S. Jin, C. Maraston, G. Magdis, M. Béthermin, M. Cappellari, M. Carollo, A. Cimatti, C. Feruglio, M. Moresco, M. Onodera, L. Pozzetti, A. Renzini, M. Sargent, F. ValentinoA. Zanella

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


We present a sample of 34 spectroscopically confirmed BzK-selected 1011 M quiescent galaxies (pBzK) in the COSMOS field. The targets were initially observed with VIMOS on the VLT to facilitate the calibration of the photometric redshifts of massive galaxies at z and 1:5. Here we describe the reduction and analysis of the data, and the spectrophotometric properties of these pBzK galaxies. In particular, using a spatially resolved median 2D spectrum, we find that the fraction of stellar populations with ages <1 Gyr is at least 3 times higher in the outer regions of the pBzK galaxies than in their cores. This results in a mild age gradient of age 0:4 Gyr over 6 kpc and suggests either the occurrence of widespread rejuvenation episodes or that inside-out quenching played a role in the passivization of this galaxy population. We also report on low-level star formation rates derived from the [OII]3727 emission line, with SFROII 3:74:5 M yr1. This estimate is confirmed by an independent measurement on a separate sample of similarly-selected quiescent galaxies in the COSMOS field, using stacked far-infrared data (SFRFIR 24 M yr1). This second, photometric sample also displays significant excess at 1.4 GHz, suggestive of the presence of radio-mode AGN activity.

Original languageEnglish
Article numberA95
JournalAstronomy and Astrophysics
StatePublished - 1 Mar 2017
Externally publishedYes


  • Galaxies: elliptical and lenticular, cD
  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: star formation
  • Galaxies: stellar content


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