English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

(Abridged) Fossil systems are group- or cluster-sized objects whoseluminosity is dominated by a very massive central galaxy. In the current colddark matter scenario, these objects formed hierarchically at an early epoch ofthe Universe and then slowly evolved until present day. That is the reason whythey are called {\it fossils}. We started an extensive observational program tocharacterize a sample of 34 fossil group candidates spanning a broad range ofphysical properties. Deep $r-$band images were taken for each candidate andoptical spectroscopic observations were obtained for $\sim$ 1200 galaxies. Thisnew dataset was completed with SDSS DR7 archival data to obtain robust clustermembership and global properties of each fossil group candidate. For eachsystem, we recomputed the magnitude gaps between the two brightest galaxies($\Delta m_{12}$) and the first and fourth ranked galaxies ($\Delta m_{14}$)within 0.5 $R_{{\rm 200}}$. We consider fossil systems those with $\Deltam_{12} \ge 2$ mag or $\Delta m_{14} \ge 2.5$ mag within the errors. We findthat 15 candidates turned out to be fossil systems. Their observationalproperties agree with those of non-fossil systems. Both follow the samecorrelations, but fossils are always extreme cases. In particular, they hostthe brightest central galaxies and the fraction of total galaxy light enclosedin the central galaxy is larger in fossil than in non-fossil systems. Finally,we confirm the existence of genuine fossil clusters. Combining our results withothers in the literature, we favor the merging scenario in which fossil systemsformed due to mergers of $L^\ast$ galaxies. The large magnitude gap is aconsequence of the extreme merger ratio within fossil systems and therefore itis an evolutionary effect. Moreover, we suggest that at least one candidate inour sample could represent a transitional fossil stage.

Fossil Groups Origins III. Characterization of the sample and observational properties of fossil systems