The Cheshire Cat Gravitational Lens: The Formation of a Massive Fossil Group

dc.contributor.authorIrwin, Jimmy A.
dc.contributor.authorDupke, Renato
dc.contributor.authorCarrasco, Eleazar R.
dc.contributor.authorMaksym, W. Peter
dc.contributor.authorJohnson, Lucas
dc.contributor.authorWhite, Raymond E. III
dc.contributor.otherUniversity of Alabama Tuscaloosa
dc.description.abstractThe Cheshire Cat is a relatively poor group of galaxies dominated by two luminous elliptical galaxies surrounded by at least four arcs from gravitationally lensed background galaxies that give the system a humorous appearance. Our combined optical/X-ray study of this system reveals that it is experiencing a line of sight merger between two groups with a roughly equal mass ratio with a relative velocity of ∼1350 km s−1 . One group was most likely a lowmass fossil group, while the other group would have almost fit the classical definition of a fossil group. The collision manifests itself in a bimodal galaxy velocity distribution, an elevated central X-ray temperature and luminosity indicative of a shock, and gravitational arc centers that do not coincide with either large elliptical galaxy. One of the luminous elliptical galaxies has a double nucleus embedded off-center in the stellar halo. The luminous ellipticals should merge in less than a Gyr, after which observers will see a massive 1.2–1.5 × 1014 M⊙ fossil group with an Mr = −24.0 brightest group galaxy at its center. Thus, the Cheshire Cat offers us the first opportunity to study a fossil group progenitor. We discuss the limitations of the classical definition of a fossil group in terms of magnitude gaps between the member galaxies. We also suggest that if the merging of fossil (or nearfossil) groups is a common avenue for creating present-day fossil groups, the time lag between the final galactic merging of the system and the onset of cooling in the shock-heated core could account for the observed lack of well-developed cool cores in some fossil groups.en_US
dc.identifier.citationIrwin, J., et al. (2015): The Cheshire Cat Gravitational Lens: The Formation of a Massive Fossil Group. The Astrophysical Journal, 806(2).
dc.subjectgalaxies: clusters: individual (SDSS J1038+4849)
dc.subjectgravitational lensing: strong
dc.subjectX-rays: galaxies: clusters
dc.titleThe Cheshire Cat Gravitational Lens: The Formation of a Massive Fossil Groupen_US
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