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第1331回 天文学教室談話会

日時

2012年05月28日(月) 15:00 pm

場所

大輪講室

講演者

Mr. Mohammad Akhlaghi (Astronomical Inst., Tohoku U.)

題目

Significant size evolution of massive quiescent galaxies in MODS

要旨

The Significant Size Evolution (SSE) in quiescent galaxies has been corroborated by some observations and not observed in others, both using the measurement of the effective radius of galaxies across cosmic history and inferring their conclusion from it. Using the very deep Subaru/MOIRCS and HST/ACS images of the GOODS-N region, from the MOIRCS Deep Survey, we attempt to simultaneously test the implications of both scenarios on the rest-frame V band image of the quiescent galaxies in our sample. As a conceptual departure from previous studies, we have not simply measured the effective radius, but assumed it, once with SSE and once without and considered the effects of the different assumptions on a second property of the galaxy light profile: the Sersic index. The Flux Ratio Analysis proposed here is based on measuring the slopes of each galaxy's profile at certain radii and comparing them with the slopes of similar magnitude profiles with various Sersic indexes and assumed effective radii. We find that if SSE is assumed, a significant evolution in n is observed; from n ? 1 at z ? 3 to the locally maintained n > 2.5 for low redshift galaxies implying that quiescent galaxies in the early universe were significantly less concentrated compared to their local counterparts. Such evolution is not observed if SSE is not assumed, in which case n remains above or about 2.5 during cosmic history.

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【The Colloquium Committee in 2012】
Shijun Yoshida (yoshida<at>astr.tohoku.ac.jp)
Masaki Takayama (m.takayama<at>astr.tohoku.ac.jp)
Hidetomo Honma (hide<at>astr.tohoku.ac.jp)
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