Star Formation in Herschel's Monsters versus Semi-Analytic Models

TL;DR

This study compares observed star formation rate functions from Herschel surveys with semi-analytic galaxy formation models, revealing good agreement up to z~2 but underprediction at higher redshifts for the brightest galaxies.

Contribution

It provides a direct comparison between observed SFRFs and semi-analytic models, highlighting discrepancies at high redshift and bright end, and suggests possible improvements in feedback modeling.

Findings

Models match observations up to z~2 when errors are considered.

All models underpredict bright-end SFRFs at z>2.

Discrepancies may be due to feedback and gas fall-back modeling issues.

Abstract

We present a direct comparison between the observed star formation rate functions (SFRF) and the state-of-the-art predictions of semi-analytic models (SAM) of galaxy formation and evolution. We use the PACS Evolutionary Probe Survey (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) data-sets in the COSMOS and GOODS-South fields, combined with broad-band photometry from UV to sub-mm, to obtain total (IR+UV) instantaneous star formation rates (SFRs) for individual Herschel galaxies up to z~4, subtracted of possible active galactic nucleus (AGN) contamination. The comparison with model predictions shows that SAMs broadly reproduce the observed SFRFs up to z~2, when the observational errors on the SFR are taken into account. However, all the models seem to under-predict the bright-end of the SFRF at z>2. The cause of this underprediction could lie in an improper modelling of several model ingredients, like too strong (AGN or stellar) feedback in the brighter objects or too low fall-back of gas, caused by weak feedback and outflows at earlier epochs.