Quenching of the star formation activity in cluster galaxies

Abstract

We study the star formation quenching mechanism in cluster galaxies by fitting the spectral energy distribution (SED) of the Herschel Reference Survey, a complete volume-limited K-band-selected sample of nearby galaxies including objects in different density regions, from the core of the Virgo cluster to the general field. The SEDs of the target galaxies were fitted using the CIGALE SED modelling code. The truncated activity of cluster galaxies was parametrised using a specific star formation history with two free parameters, the quenching age QA and the quenching factor QF. These two parameters are crucial for the identification of the quenching mechanism, which acts on long timescales when starvation processes are at work, but is rapid and efficient when ram pressure occurs. To be sensitive to an abrupt and recent variation of the star formation activity, we combined twenty photometric bands in the UV to far-infrared in a new way with three age-sensitive Balmer line absorption indices extracted from available medium-resolution (R ∼ 1000) integrated spectroscopy and with Hα narrow-band imaging data. The use of a truncated star formation history significantly increases the quality of the fit in HI-deficient galaxies of the sample, that is to say, in those objects whose atomic gas content has been removed during the interaction with the hostile cluster environment. The typical quenching age of the perturbed late-type galaxies is QA < ∼ 300 Myr whenever the activity of star formation is reduced by 50% < QF ≤ 80% and QA < ∼ 500 Myr for QF > 80%, while that of the quiescent early-type objects is QA 1−3 Gyr. The fraction of late-type galaxies with a star formation activity reduced by QF > 80% and with an HI-deficiency parameter HI − de f > 0.4 drops by a factor of ∼5 from the inner half virial radius of the Virgo cluster (R/R vir < 0.5), where the hot diffuse X-ray emitting gas of the cluster is located, to the outer regions (R/R vir > 4). The efficient quenching of the star formation activity observed in Virgo suggests that the dominant stripping process is ram pressure. We discuss the implication of this result in the cosmological context of galaxy evolution.

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

“…NGC 4330 (VCC 630) is a highly inclined (84 deg), intermediate mass (M * 10 9.7 M , Boselli et al 2016b) Scd galaxy in the Virgo cluster located at a projected distance of 600 kpc (0.4 × r vir ) from M87. Spatially resolved radio observations made with the Very Large Array in C+D configuration have revealed the presence of a long tail of HI gas (Chung et al 2007) on the trailing side of the interaction, pointing in an opposite direction with respect to M87.…”

“…We make use of two independently developed codes. The first performs a joint fitting of spectra and photometry using Monte Carlo techniques to optimally explore the parameter space and the second code fits only the photometric data points plus the integrated flux in the Hα line, as first introduced in Boselli et al (2016b).…”

“…However, for satellite galaxies in massive clusters of galaxies, several authors have found shorter (1 − 2 Gyr) quenching timescales (Boselli et al 2016b;Oman & Hudson 2016). Although the different methods make the comparison to the delayed+rapid quenching model non-trivial, it is generally found that both the delay and the fading phases get shorter once the effect of quenching in haloes different from the cluster environment are taken into account (Oman & Hudson 2016).…”

“…els for the growth and quenching of disc galaxies as a function of radius. We test our new code by comparing it with the results from CIGALE (Noll et al 2009), a fitting code which has already been used to characterise the quenching histories of galaxies in cluster environments (Boselli et al 2016b). In section 2, we present the target galaxy and the photometric and spectroscopic data we use in this paper, and in section 3 we describe the properties of the Hα tail discovered by the VESTIGE observations.…”

GASP. III. JO36: A Case of Multiple Environmental Effects at Play?

“…Furthermore, it is a more fair representation of the stellar populations evolution, the SFH of galaxies being in general characterized by various episodes of star formation of different intensity at various ages, especially when galaxies in dense environments are considered (see e.g. Boselli et al 2016).…”