The imprint of rapid star formation quenching on the spectral energy distributions of galaxies

Abstract

In high density environments, the gas content of galaxies is stripped, leading to a rapid quenching of their star formation activity. This dramatic environmental effect, which is not related to typical passive evolution, is generally not taken into account in the star formation histories (SFHs) usually assumed to perform spectral energy distribution (SED) fitting of these galaxies, yielding a poor fit of their stellar emission and, consequently, biased estimate of the star formation rate (SFR). In this work, we aim at reproducing this rapid quenching using a truncated delayed SFH that we implemented in the SED fitting code CIGALE. We show that the ratio between the instantaneous SFR and the SFR just before the quenching (r SFR ) is well constrained as long as rest-frame UV data are available. This SED modeling is applied to the Herschel Reference Survey (HRS) containing isolated galaxies and sources falling in the dense environment of the Virgo cluster. The latter are H-deficient because of ram pressure stripping. We show that the truncated delayed SFH successfully reproduces their SED, while typical SFH assumptions fail. A good correlation is found between r SFR and H−de f , the parameter that quantifies the gas deficiency of cluster galaxies, meaning that SED fitting results can be used to provide a tentative estimate of the gas deficiency of galaxies for which H observations are not available. The HRS galaxies are placed on the SFR-M * diagram showing that the H-deficient sources lie in the quiescent region, thus confirming previous studies. Using the r SFR parameter, we derive the SFR of these sources before quenching and show that they were previously on the main sequence relation. We show that the r SFR parameter is also recovered well for deeply obscured high redshift sources, as well as in the absence of IR data. SED fitting is thus a powerful tool for identifying galaxies that underwent a rapid star formation quenching.

Quenching of the star formation activity in cluster galaxies

“…The observed SED of the HRS galaxies are fitted using the CIGALE 2 SED modelling code (Noll et al 2009;Ciesla et al 2016;Boquien et al, in prep.). Its application to the HRS galaxies has been described in detail in Ciesla et al (2014Ciesla et al ( , 2016.…”

“…Its application to the HRS galaxies has been described in detail in Ciesla et al (2014Ciesla et al ( , 2016. Here we briefly summarise the main properties of this code.…”

“…This code has been successfully used to reconstruct the star formation history of high-z and local galaxies Boquien et al 2016;Lo Faro et al, in prep. ), including those of the HRS (Boquien et al 2012(Boquien et al , 2013Ciesla et al 2014Ciesla et al , 2016.…”

“…To reproduce the quenching of the star formation activity of the Virgo cluster galaxies, we used a formalism similar to the one proposed in Ciesla et al (2016), that is, we applied an instantaneous truncation of the star formation history parametrised by the expression…”

“…In this work we improve this SED fitting code to combine in an original manner twenty photometric bands of imaging data with three agesensitive spectroscopic indices (Balmer absorption lines) derived from integrated spectroscopy ) and narrowband Hα imaging data (Boselli et al 2015) with the aim of characterising the quenching star formation episode. We previously explored the use of the SED fitting analysis to reproduce the variations on the star formation history of cluster galaxies using only broad-band imaging photometry in Ciesla et al (2016). The present work is thus a further developement of this technique.…”