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

Journal article

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.

Authors: Gobat, R; Daddi, E; Strazzullo, V; Garilli, B; Mignoli, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: EDP Sciences
• Journal: Astronomy & Astrophysics
• Volume: 599
• Pages: A95
• Publication date: 2017-03-01
• Acceptance date: 2016-12-20
• DOI: 10.1051/0004-6361/201629852
• ISSN: 0004-6361 and 1432-0746
• Language: English
• Keywords: galaxies: star formation; galaxies: elliptical and lenticular, cD; galaxies: stellar content; galaxies: high-redshift; galaxies: formation