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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 709866.0, MPI für Astronomie / Publikationen_mpia
How dead are dead galaxies? Mid-infrared fluxes of quiescent galaxies at redshift 0.3 < z < 2.5: Implications for star formation rates and dust heating
Authors:Fumagalli, M.; Labbé, I.; Patel, S. G.; Franx, M.; van Dokkum, P.; Brammer, G.; da Cunha, E.; Förster Schreiber, N. M.; Kriek, M.; Quadri, R.; Rix, H.-W.; Wake, D.; Whitaker, K. E.; Lundgren, B.; Marchesini, D.; Maseda, M.; Momcheva, I.; Nelson, E.; Pacifici, C.; Skelton, R. E.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:The Astrophysical Journal
Start Page:id. 35 (11 pp)
Audience:Not Specified
Abstract / Description:We investigate star formation rates (SFRs) of quiescent galaxies at high redshift (0.3 < z < 2.5) using 3D-HST WFC3 grism spectroscopy and Spitzer mid-infrared data. We select quiescent galaxies on the basis of the widely used UVJ color-color criteria. Spectral energy distribution (SED) fitting (rest-frame optical and near-IR) indicates very low SFRs for quiescent galaxies (sSFR ~ 10-12 yr-1). However, SED fitting can miss star formation if it is hidden behind high dust obscuration and ionizing radiation is re-emitted in the mid-infrared. It is therefore fundamental to measure the dust-obscured SFRs with a mid-IR indicator. We stack the MIPS 24 mum images of quiescent objects in five redshift bins centered on z = 0.5, 0.9, 1.2, 1.7, 2.2 and perform aperture photometry. Including direct 24 mum detections, we find sSFR ~ 10-11.9 × (1 + z)4 yr-1. These values are higher than those indicated by SED fitting, but at each redshift they are 20-40 times lower than those of typical star-forming galaxies. The true SFRs of quiescent galaxies might be even lower, as we show that the mid-IR fluxes can be due to processes unrelated to ongoing star formation, such as cirrus dust heated by old stellar populations and circumstellar dust. Our measurements show that star formation quenching is very efficient at every redshift. The measured SFR values are at z > 1.5 marginally consistent with the ones expected from gas recycling (assuming that mass loss from evolved stars refuels star formation) and well below that at lower redshifts.
Free Keywords:galaxies: evolution; galaxies: formation
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/0004-637X/796/1/35
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