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Subaru Seminars are usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you would like to give a seminar, please contact Subaru seminar organizers (Thayne Currie, Tae-Soo Pyo, Nagayoshi Ohashi) by email : (please change"_at" to @).

April 13, Thursday, 11am in 104B

" Searching for Strong Lenses to Probe Dark Matter Substructures "

James Chan

(NTU, Taiwan)

Galaxy clusters trace the most massive dark matter halos and the densest galaxy environment, hence are invaluable cosmological probes, and also ideal laboratories to study environmental effects on galaxy evolution. Galaxy clusters in the local universe (and up to z~1.5) are exclusively dominated by massive ellipticals in the core. Both galaxy cluster archaeology and cosmological simulations suggest that these galaxies formed in a short time scale at z>~2, however, structures with clear evidence suggestive of such a rapid formation phase have been lacking so far, and the (trans)formation mechanisms of cluster ellipticals remain a mystery. In this talk I will present our recent discovery of the most distant galaxy cluster known to date at z=2.51(named “CLJ1001”, 17 confirmed members). In addition to its record-breaking distance, CLJ1001 is the first X-ray cluster discovered so far that is dominated by massive star-forming galaxies in the core (instead of massive ellipticals found in low-redshift clusters). With an exceptional star formation rate of ~3400 Msun/yr and a gas depletion time of ~200 Myrs in the cluster core, CLJ1001 was caught in a rapid formation phase of cluster ellipticals, and likely represents a critical transition phase between young, proto-clusters and mature clusters. I will discuss what we have learned so far on CLJ1001 from extensive follow-up observations with ALMA, IRAM-NOEMA, VLA, and VLT, focusing on its implications on the formation of massive cluster ellipticals.

Seminars are also held at JAC, CFHT, and IfA.

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