The complex physics of dusty star-forming galaxies at high redshifts as revealed by Herschel and Spitzer
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing
Abstract
We combine far-infrared photometry from Herschel (PEP/HerMES) with deep mid-infrared spectroscopy from
Spitzer to investigate the nature and the mass assembly history of a sample of 31 luminous and ultraluminous
infrared galaxies ((U)LIRGs) at z ∼ 1 and 2 selected in GOODS-S with 24μm fluxes between 0.2 and 0.5 mJy.We
model the data with a self-consistent physical model (GRASIL) which includes a state-of-the-art treatment of dust
extinction and reprocessing. We find that all of our galaxies appear to require massive populations of old (>1 Gyr)
stars and, at the same time, to host a moderate ongoing activity of star formation (SFR 100M yr−1). The bulk of
the stars appear to have been formed a few Gyr before the observation in essentially all cases. Only five galaxies of
the sample require a recent starburst superimposed on a quiescent star formation history.We also find discrepancies
between our results and those based on optical-only spectral energy distribution (SED) fitting for the same objects;
by fitting their observed SEDs with our physical model we find higher extinctions (by ΔAV ∼ 0.81 and 1.14)
and higher stellar masses (by Δlog(M ) ∼ 0.16 and 0.36 dex) for z ∼ 1 and z ∼ 2 (U)LIRGs, respectively. The
stellar mass difference is larger for the most dust-obscured objects. We also find lower SFRs than those computed
from LIR using the Kennicutt relation due to the significant contribution to the dust heating by intermediate-age
stellar populations through “cirrus” emission (∼73% and ∼66% of the total LIR for z ∼ 1 and z ∼ 2 (U)LIRGs,
respectively).
Description
Keywords
Galaxies, Evolution – galaxies, General – galaxies, Interactions – galaxies, Starburst
Citation
Lo Faro, B. et al. (2013). The complex physics of dusty star-forming galaxies at high redshifts as revealed by Herschel and Spitzer. The Astrophysical Journal , 762 (108): 1-13