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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 (Tadayuki Kodama, Kumiko S. Usuda, Naoyuki Tamura, Tomonori Usuda) by email : sseminar_at_subaru.naoj.org (please change"_at" to @).

June 24, Thursday at 11:00 am

" MAHALO-Subaru I: Panoramic H-alpha Imaging Survey for Intermediate-Redshift Clusters "

Yusei Koyama (University of Tokyo)


In our series of talks, we present the recent progress of our newly launched "MAHALO-Subaru" project (MApping HAlpha and Lines of Oxygen with Subaru). We aim to study the star forming activity of galaxies via H-alpha and/or [OII] lines in various environments (i.e. from cluster to field) at z ~ 0.4-2.5, exploiting the narrow-band filters installed on the Subaru Telescope. In my talk, I will focus on the results from our H-alpha imaging survey for two galaxy clusters at z=0.4 and z=0.8. Taking advantage of the wide-field capability of Subaru, we map out the star forming activity in and around the clusters. In particular, we found a large number of red star forming galaxies (probably the transition galaxies) especially in galaxy groups and/or in the filamentary structures relatively far away from the cluster. Our results suggest that properties of galaxies are indeed changing 'before' entering cluster environment and that group environment at z<1 may have played an important role in the evolution of the present-day cluster galaxies.

" MAHALO-Subaru II: Panoramic [OII] Imaging Survey for a high-z cluster at z=1.46 "

Masao Hayashi (NAOJ)


We are executing "MAHALO-Subaru" project (MApping HAlpha and Lines of Oxygen with Subaru) to reveal star formation activities in different environments at z~0.4-2.5 comprehensively. In my talk, I will present a [OII] emission survey for XMMXCS J2215.9-1738 cluster at z=1.46, which is one of highest-redshift clusters, with a narrow-band filter on Subaru/Suprime-Cam. We found a large scale structure of [OII] emitters from east to south of the cluster. Interestingly, we also found that there are many [OII] emitters even in the central high-density region of the cluster, suggesting active star formation in the cluster core. On the other hand, it is revealed that such star formation is not seen in high density regions at lower redshifts. I will discuss the star forming activities in and around this high-z cluster, and present the implication that galaxy formation is biased in a core of high-z clusters.

" MAHALO-Subaru III: The survey of H-alpha emitters in GOODS-N field at z=2.2 "

Ken-ichi Tadaki (University of Tokyo/NAOJ


We have started a new project, "MAHALO-Subaru" (MApping HAlpha and Lines of Oxygen with Subaru). In my talk, I will make a presentation of the H-alpha emitter survey in a blank field with a custom-made narrow-band filter on MOIRCS. From this survey, we have identified 12 H-alpha emitters at z=2.2 on the basis of a narrow-band excess and photometric redshift. Most of them have been confirmed by spectroscopic follow-up. Our samples are not homogeneously distributed across field. In our project, there are large samples of star-forming galaxies in various environments and redshifts. For these galaxies, we have estimated the stellar mass and star formation rate in the same but different method and compared the results in the low density regions to those in the high density regions. This result suggests that the evolution of star formation activity is different among environments.


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



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