An S-shaped arc in the galaxy cluster RX J0054.0-2823

Monthly Notices of the Royal Astronomical Society

Giraud

Toledo

et al. 2012

Self Cite

A substantial fraction of the total stellar mass in rich clusters of galaxies resides in a diffuse intergalactic component usually referred to as the Intra-Cluster Light (ICL). Theoretical models indicate that these intergalactic stars originate mostly from the tidal interaction of the cluster galaxies during the assembly history of the cluster, and that a significant fraction of these stars could have formed in-situ from the late infall of cold metal-poor gas clouds onto the cluster. The models make predictions about the age distribution of the ICL stars, which may provide additional observational constraints. However, these models also over-predict the fraction of stellar mass in the ICL by a substantial margin. Here we present population synthesis models for the ICL of a dumb-bell dominated intermediate redshift (z=0.29) X-ray cluster for which we have deep MOS data obtained with the FORS2 instrument. In a previous paper we have proposed that the dumbell galaxy act as a grinding machine tearing to pieces the galaxies that pass nearby thus enriching the intergalactic medium. In this paper we analyze the spectra at different locations within the ICL and find that it is dominated by old metal rich stars, at odds with what has been found in nearby clusters where the stars that dominate the ICL are old and metal poor. While we see a weak evidence of a young, metal poor, component, if real, these young stars would amount to less than 1% of the total ICL mass, much less than the up to 30% predicted by the models. We propose that the very metal rich (i.e. 2.5 times solar) stars in the ICL of our cluster, which comprise approximately 40% of the total mass, originate mostly from the central dumb-bell galaxy, while the remaining solar and metal poor stars come from spiral, post-starburst (E+A), and metal poor dwarf galaxies. About 16% of the ICL stars are old and metal poor.Comment: 10 pages, 6 figure

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Intergalactic stellar populations in intermediate redshift clusters

Monthly Notices of the Royal Astronomical Society

Giraud

Toledo

et al. 2012

Self Cite

“…In the course of an investigation of the diffuse intergalactic light in X‐ray emitting clusters at intermediate redshifts, we detected a puzzling S‐shaped arc‐like structure in the ROSAT cluster RX J0054.0−2823 that we tentatively identified as the gravitationally lensed image of a background galaxy at a redshift between z = 0.5 and 1.0 (Faure et al 2007). The cluster is characterized by having three dominant D class galaxies, two of which are interacting forming a dumbbell cD system.…”

Section: Introductionmentioning

confidence: 97%

Diffuse intracluster light at intermediate redshifts: intracluster light observations in an X-ray cluster at z= 0.29★

Toledo

Monthly Notices of the Royal Astronomical Society

Selman

et al. 2011

Self Cite

The diffuse intracluster light (ICL) contains a significant fraction of the total stellar mass in clusters of galaxies, and contributes in roughly equal proportion as the hot intracluster medium to the total baryon content of clusters. Because of the potential importance of understanding the origin of the ICL in the context of the formation and evolution of structure in the Universe, the field has recently undergone a revival both in the quality and quantity of observational and theoretical investigations. Because of cosmological dimming, the observational work has mostly concentrated on low‐redshift clusters, but clearly observations at higher redshifts can provide interesting clues about the evolution of the diffuse component. In this paper we present the first results of a programme to characterize the ICL of intermediate‐redshift clusters. We find that at z∼ 0.3, the X‐ray cluster RX J0054.0−2823 already has a significant ICL and that the fraction of the total light in the ICL and the brightest cluster galaxy (BCG) is comparable to that of similar clusters at lower redshift. We also find that the kinematics of the ICL is consistent with it being the remnant of tidally destroyed galaxies streaming in the central regions of the cluster, which has three central giant elliptical galaxies acting as an efficient ‘galaxy grinding machine’. Our cluster has a bi‐modal radial velocity distribution and thus two possible values for the velocity dispersion. We find that the cluster fits well in the correlation between BCG+ICL fraction and cluster mass for a range of velocity dispersions, leading us to question the validity of a relevant correlation between these two quantities.

“…In the course of an investigation of the diffuse intergalactic light in X-ray emitting clusters at intermediate redshifts (Melnick et al 1999), we detected a puzzling S-shaped arc-like structure in the ROSAT cluster RX J0054.0-2823 (Faure et al 2007), which we tentatively identified as the gravitationally lensed image of a background galaxy at a redshift between z=0.5 and z=1.0. The cluster, however, is characterized by having three dominant D or cD galaxies in the center, two of which are clearly interacting.…”

Section: Introductionmentioning

confidence: 86%

Low-ionization galaxies and evolution in a pilot survey up toz= 1

Giraud

Res. Astron. Astrophys.

et al. 2011

We present galaxy spectroscopic data on a pencil beam of 10.75 ′ × 7.5 ′ centered on the X-ray cluster RXJ0054.0-2823 at z = 0.29. We study the spectral evolution of galaxies from z = 1 down to the cluster redshift in a magnitude-limited sample at R ≤ 23, for which the statistical properties of the sample are well understood. We divide emission-line galaxies in star-forming galaxies, LINERs, and Seyferts by using emissionline ratios of [OII], Hβ, and [OIII], and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies. For absorptionline galaxies we recover the well known result that these galaxies have had no detectable evolution since z ∼ 0.6 − 0.7, but we also find that in the range z = 0.65 − 1 at least 50% of the stars in bright absorption systems are younger than 2.5Gyr. Faint absorption-line galaxies in the cluster at z = 0.29 also had significant star formation during the previous 2-3Gyr, while their brighter counterparts seem to be composed only of old stars. At z ∼ 0.8, our dynamically young cluster had a truncated red-sequence. This result seems to be consistent with a scenario where the final assembly of E/S0 took place at z < 1. In the volume-limited range 0.35 ≤ z ≤ 0.65 we find that 23% of the early-type galaxies have LINER-like spectra with Hβ in absorption and a significant component of A stars. The vast majority of LINERs in our sample have significant populations of young and intermediate-aged stars and are thus not related to AGN, but to the population of 'retired galaxies' recently identified by Cid-Fernandes et al. (2010) in the SDSS. Early-type LINERs with various fractions of A stars, and E+A galaxies appear to play an important role in the formation of the red sequence.