![]() (2014) found identical behaviors for regular groups and FGs when they considered the relation between their X-ray and optical luminosities, which suggests that FGs contain the same amount of optical material than traditional groups, but that it is concentrated in a giant elliptical galaxy that has cannibalized most surrounding bright galaxies early on. 2018) or optical properties (e.g., Santos et al. Fossil groups can be studied through their X-ray (e.g., Adami et al. The situation is not simpler on the observational side, partly because we lack large samples of FGs, and partly because selection criteria differ. (2005), some clues also exist that FGs might be a temporary stage of group evolution before they capture more galaxies in their vicinity, as reported for instance by von Benda-Beckmann et al. Although this scenario was supported by some hydrodynamical simulations by D’Onghia et al. (2003) is that FGs are the remnants of early mergers, and that they are cool-core structures which a long time ago accreted most of the large galaxies in their environment. An open question is the formation of these peculiar objects and why they present such a low amount of optically emitting matter.Īn early explanation that has been proposed by Jones et al. (2003) later defined FGs as extended X-ray sources with an X-ray luminosity of at least, and a brightest group galaxy (BGG) at least two magnitudes brighter than all other group members. (1994) reported the first observation of such an object. Introductionįossil groups (FGs) are puzzling large-scale structures which present high X-ray luminosities but fewer bright optical galaxies than groups or clusters of galaxies. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Being in a poor environment might therefore be the driver of FG formation because the number of nearby galaxies is not sufficient to compensate for the cannibalism of the central group galaxy. They seem to reside closely to cosmic filaments and do not survive in nodes. We confirm that FGs have low masses and are rare. They are preferentially four times more distant from their nearest node than from their nearest filament.Ĭonclusions. Overall, structures with PFG ≥ 50% are located close to the cosmic web filaments (87% are located closer than 1 Mpc to their nearest filament). We find that structures with masses lower than 2.4 × 10 14 M ⊙ have the highest probabilities of being fossil groups (PFG). We analyzed the mass distribution of these candidate FGs, and estimated their distance to the filaments and nodes of the cosmic web in which they are embedded. Based on spectroscopic and photometric redshifts, we estimated the probability of galaxies to belong to a galaxy structure, and by imposing the condition that the brightest group galaxy is at least brighter than the others by two magnitudes, we computed the probability for a given galaxy structure to be a FG. We propose here a probabilistic analysis of FGs, extracted from the large catalog of candidate groups and clusters previously detected in the CFHTLS survey based on photometric redshifts to investigate their position in the cosmic web and probe their environment. However, the scenario of their formation remains controversial.Īims. Fossil groups (FGs) have been discovered 25 years ago, and are now defined as galaxy groups with an X-ray luminosity higher than erg s −1 and a brightest group galaxy brighter than the other group members by at least two magnitudes. Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis Bd Arago, 75014 Paris, FranceĬontext. Durret 3Īix Marseille Univ, CNRS, CNES, LAM, Marseille, FranceĮ-mail: of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK Astronomical objects: linking to databasesĬ.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
0 Comments
Leave a Reply. |