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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tomonori Usuda, Kumiko S. Usuda, Masayuki Akiyama) by email : sseminar_at_subaru.naoj.org (please change"_at" to @).

August 30, Wednesday at 11:30am

" Spitzer Observations of the Brightest Galaxies in X-Ray-Luminous Clusters: Implications for Cluster Cooling Flows "

Eiichi Egami

(Steward Observatory, University of Arizona)


In the cores of X-ray-luminous clusters of galaxies, estimated radiative gas cooling times are often significantly shorter than the Hubble time, suggesting the possibility that these clusters sustain a flow of cooling gas accreting onto the brightest cluster galaxy (BCG) at the cluster center (i.e., a cluster cooling flow). I will present the results from our Spitzer cluster program, showing that the BCGs located in clusters with an extremely short gas cooling time (< 1 Gyr) are IR-luminous, which is consistent with the idea that a cluster cooling flow is triggering the infrared activity in these BCGs. Judged from the Spitzer/IRS spectrum taken for one such IR-luminous BCG, the source of the infrared luminosity is star formation (e.g., strong PAH emission). Furthermore, the spectrum shows abnormally strong pure-rotational molecular hydrogen (H2) emission lines (likely shock-excited) with a corresponding warm H2 gas mass of 10^{10} Msun, the largest known to date. Together, these results indicate that the BCGs in strongly cooling cluster cores are unusually active, and suggest that their IR properties are intimately connected to the intracluster gas cooling process.
I will also describe briefly another on-going Spitzer cluster project to study gravitationally lensed high-redshift galaxies.


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



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