Related papers: Are fossil groups a challenge of the Cold Dark Mat…
Fossil groups are systems with one single central elliptical galaxy and an unusual lack of luminous galaxies in the inner regions. The standard explanation for the formation of these systems suggests that the lack of bright galaxies is due…
Defined as X-ray bright galaxy groups with large differences between the luminosities of their brightest and second brightest galaxies, "fossil groups" are believed to be some of the oldest galaxy systems in the universe. They have…
We report the discovery of seven new fossil systems in the 400d cluster survey. Our search targets nearby, $z\le0.2$, and X-ray bright, $L_X\ge 10^{43}$ erg sec$^{-1}$, clusters of galaxies. Where available, we measure the optical…
(Abridged) Fossil systems are group- or cluster-sized objects whose luminosity is dominated by a very massive central galaxy. In the current cold dark matter scenario, these objects formed hierarchically at an early epoch of the Universe…
This paper presents both the result of a search for fossil systems (FSs) within the XMM Cluster Survey and the Sloan Digital Sky Survey and the results of a study of the stellar mass assembly and stellar populations of their fossil…
We describe the properties of a sample of galaxy groups with very unusual distributions of galaxy luminosities. The most extreme example has an X-ray luminosity similar to that of the Virgo cluster but has a very low richness, with only one…
We use large cosmological N-body simulations to study the subhalo population in galaxy group sized halos. In particular, we look for fossil group candidates with typical masses ~10-25% of Virgo cluster but with an order of magnitude less…
We present a detailed X-ray and optical study of a distant fossil system RX J1416.4+2315 (z=0.13), combining Chandra and XMM-Newton observations, optical photometry and spectroscopy. X-ray emitting hot gas imaged by both the Chandra and…
We determine the first fossil group luminosity function based on spectroscopy of the member galaxies. The fossil group RX J1552.2+2013 has 36 confirmed members, it is at a mean redshift of 0.136 and has a velocity dispersion of 623 km/s (or…
It is thought that fossil systems are relics of structure formation in the primitive Universe. They are galaxy aggregations that have assembled their mass at high redshift with few or no subsequent accretion. Observationally these systems…
We report the discovery of 12 new fossil groups of galaxies, systems dominated by a single giant elliptical galaxy and cluster-scale gravitational potential, but lacking the population of bright galaxies typically seen in galaxy clusters.…
Fossil galaxy groups are spatially extended X-ray sources with X-ray luminosities above L_X,bol > 10^42 h_50^-2 ergs s^-1 and a central elliptical galaxy dominating the optical, the second-brightest galaxy being at least 2 magnitudes…
We collected multiband imaging and spectroscopy for two fossil groups (RX J1119.7+2126 and 1RXS J235814.4+150524) and one normal group (NGC 6034). We computed photometric redshifts in the central zones of each group, combining previous data…
Fossil systems are defined to be X-ray bright galaxy groups with a 2-magnitude difference between their two brightest galaxies within half the projected virial radius,and represent an interesting extreme of the population of galaxy…
The luminosity gap between the two brightest members of galaxy groups and clusters is thought to offer a strong test for the models of galaxy formation and evolution. This study focuses on the statistics of the luminosity gap in galaxy…
The most accepted scenario for the origin of fossil groups (FGs) is that they are galaxy associations in which the merging rate was fast and efficient. These systems have assembled half of their mass at early epoch of the Universe,…
We present the first pointed X-ray observations of 10 candidate fossil galaxy groups and clusters. With these Suzaku observations, we determine global temperatures and bolometric X-ray luminosities of the intracluster medium (ICM) out to…
We use SDSS-DR4 photometric and spectroscopic data out to redshift z~0.1 combined with ROSAT All Sky Survey X-ray data to produce a sample of twenty-five fossil groups (FGs), defined as bound systems dominated by a single, luminous…
This study is part of the FOssil Groups Origin (FOGO) project which aims at carrying out a systematic and multiwavelength study of a large sample of fossil systems. Here we focus on the relation between the optical luminosity (Lopt) and…
We study the properties of the fossil cluster RX J1416.4+2315 through g' and i'-band imaging and spectroscopy of 25 member galaxies. The system is at a mean redshift of 0.137 and has a velocity dispersion of 584 km s^-1. Superimposed onto…