Journal Article

Mapping dusty star formation in and around a cluster at <i>z</i>= 0.81 by wide-field imaging with AKARI

Yusei Koyama, Tadayuki Kodama, Kazuhiro Shimasaku, Sadanori Okamura, Masayuki Tanaka, Hyung Mok Lee, Myungshin Im, Hideo Matsuhara, Toshinobu Takagi, Takehiko Wada and Shinki Oyabu

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 4, pages 1758-1770
Published in print December 2008 | ISSN: 0035-8711
Published online December 2008 | e-ISSN: 1365-2966 | DOI:
Mapping dusty star formation in and around a cluster at z= 0.81 by wide-field imaging with AKARI

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We present environmental dependence of dusty star-forming activity in and around the cluster RXJ1716.4+6708 at z= 0.81 based on wide-field and multiwavelength observations with the Prime Focus Camera on the Subaru Telescope (Suprime-Cam) and the Infrared Camera onboard the AKARI satellite. Our optical data show that the optical colour distribution of galaxies starts to dramatically change from blue to red at the medium-density environment such as cluster outskirts, groups and filaments. By combining with the AKARI infrared data, we find that 15-μm-detected galaxies tend to have optical colours between the red sequence and the blue cloud with a tail into the red sequence, consistent with being dusty star-forming galaxies.

The spatial distribution of the 15-μm-detected galaxies over ∼200 arcmin2 around the cluster reveals that few 15-μm galaxies are detected in the cluster central region. This is probably due to the low star-forming activity in the cluster core. However, interestingly, the fraction of 15-μm-detected galaxies in the medium-density environments is as high as in the low-density field, despite the fact that the optical colours start to change in the medium-density environments. Furthermore, we find that 15-μm-detected galaxies which have optically red colours (candidates for dusty red galaxies) and galaxies with high specific star formation rates are also concentrated in the medium-density environment. These results imply that the star-forming activity in galaxies in groups and filaments is enhanced due to some environmental effects specific to the medium-density environment (e.g. galaxy–galaxy interaction), and such a phenomenon is probably directly connected to the truncation of star-forming activity in galaxies seen as the dramatic change in optical colours in such environment.

Keywords: galaxies: clusters: individual: RXJ1716.4+6708; galaxies: evolution; galaxies: starburst; large-scale structure of Universe

Journal Article.  11138 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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