The XXL Survey

Abstract

Aims. Within a cluster, gravitational effects can lead to the removal of stars from their parent galaxies and their subsequent dispersal into the intracluster medium. Gas hydrodynamical effects can additionally strip gas and dust from galaxies; both gas and stars contribute to intracluster light (ICL). The properties of the ICL can therefore help constrain the physical processes at work in clusters by serving as a fossil record of the interaction history. Methods. The present study is designed to characterise this ICL for the first time in a ∼10 14 M and z ∼ 0.53 cluster of galaxies from imaging and spectroscopic points of view. By applying a wavelet-based method to CFHT Megacam and WIRCAM images, we detect significant quantities of diffuse light and are able to constrain their spectral energy distributions. These sources were then spectroscopically characterised with ESO Multi Unit Spectroscopic Explorer (MUSE) spectroscopic data. MUSE data were also used to compute redshifts of 24 cluster galaxies and search for cluster substructures.Results. An atypically large amount of ICL, equivalent in i to the emission from two brightest cluster galaxies, has been detected in this cluster. Part of the detected diffuse light has a very weak optical stellar component and apparently consists mainly of gas emission, while other diffuse light sources are clearly dominated by old stars. Furthermore, emission lines were detected in several places of diffuse light. Our spectral analysis shows that this emission likely originates from low-excitation parameter gas. Globally, the stellar contribution to the ICL is about 2.3 × 10 9 yr old even though the ICL is not currently forming a large number of stars. On the other hand, the contribution of the gas emission to the ICL in the optical is much greater than the stellar contribution in some regions, but the gas density is likely too low to form stars. These observations favour ram pressure stripping, turbulent viscous stripping, or supernovae winds as the origin of the large amount of intracluster light. Since the cluster appears not to be in a major merging phase, we conclude that ram pressure stripping is the most plausible process that generates the observed ICL sources. Conclusions. This is one of the first times that we are able to spectroscopically study diffuse light in such a distant and massive cluster, and it demonstrates the potential of MUSE observations for such studies.

Intracluster light at the Frontier – II. The Frontier Fields Clusters

“…If we assume that the stellar populations of the BCG(s) were formed at z ∼ 2 − 3, then the observed age difference is compatible with the ICL being assembled at z < 1. The measured ages for the ICL are consistent with the ages (∼ 2.5 Gyr) derived spectroscopically by Toledo et al (2011) for a cluster at z ∼ 0.29 and Adami et al (2016) for a cluster at z ∼ 0.53 (2.3 Gyr).…”

Spectroscopic Constraints on the Buildup of Intracluster Light in the Coma Cluster

“…Deep imaging and accurate sky subtraction are required to detect the ICL and constrain its growth over time (Gonzalez et al 2005;Mihos et al 2005;Zibetti et al 2005;Rudick et al 2010;Toledo et al 2011;Guennou et al 2012;Giallongo et al 2014;Burke et al 2015). The stellar population and kinematic properties have been explored through multiwavelength photometry (Williams et al 2007;Montes & Trujillo 2014, integral-field spectroscopy (Adami et al 2016;Edwards et al 2016), globular clusters (Alamo-Martínez & Blakeslee 2017), and individual objects such as planetary nebulae (Arnaboldi et al 2003(Arnaboldi et al , 2004Feldmeier et al 2004;Gerhard et al 2007) and red giant branch stars (Williams et al 2007;Longobardi et al 2015).…”

Ionised gas structure of 100 kpc in an over-dense region of the galaxy group COSMOS-Gr30 at z ~ 0.7

“…In previous studies of extended ionised gas structures that were discovered at various redshifts, integral field spectroscopy has been commonly used to map spectral and kinematics properties of these structures using various lines without any assumption on their distribution (e.g. Cheung et al 2016;Fensch et al 2016;Lin et al 2017;Weijmans et al 2010;Borisova et al 2016;Iglesias-Páramo et al 2012;Rodríguez-Baras et al 2014;Adami et al 2016). Studying line diagnostics with integral field spectroscopy allows one to constrain the abundance and hence the origin of the gas, as well as the energetics of the ionising sources of these structures at any location.…”