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arXiv · 1704.05962

Bimodal morphologies of massive galaxies at the core of a protocluster at z=3.09 and the strong size growth of a brightest cluster galaxy

M. Kubo·T. Yamada·T. Ichikawa·M. Kajisawa·Y. Matsuda·I. Tanaka·H. Umehata
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Abstract

We present the near-infrared high resolution imaging of an extremely dense group of galaxies at the core of the protocluster at $z=3.09$ in the SSA22 field by using the adaptive optics AO188 and the Infrared Camera and Spectrograph (IRCS) on Subaru Telescope. Wide morphological variety of them suggests their on-going dramatic evolutions. One of the two quiescent galaxies (QGs), the most massive one in the group, is a compact elliptical with an effective radius $r_{e} = 1.37\pm0.75$ kpc. It supports the two-phase formation scenario of giant ellipticals today that a massive compact elliptical is formed at once and evolves in the size and stellar mass by series of mergers. Since this object is a plausible progenitor of a brightest cluster galaxy (BCG) of one of the most massive clusters today, it requires strong size ($\ga10$) and stellar mass ($\sim$ four times by $z=0$) growths. Another QG hosts an AGN(s) and is fitted with a model composed from an nuclear component and Sérsic model. It shows spatially extended [O{\footnotesize III}]$λ$5007 emission line compared to the continuum emission, a plausible evidence of outflows. Massive star forming galaxies (SFGs) in the group are two to three times larger than the field SFGs at similar redshift. Although we obtained the $K$-band image deeper than the previous one, we found no candidate new members. This implies a physical deficiency of low mass galaxies with stellar mass $M_{\star}\la4\times10^{10}~M_{\odot}$ and/or poor detection completeness of them owing to their diffuse morphologies.

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M. Kubo, T. Yamada, T. Ichikawa, M. Kajisawa, Y. Matsuda, I. Tanaka, H. Umehata. 2017-04-20. Bimodal morphologies of massive galaxies at the core of a protocluster at z=3.09 and the strong size growth of a brightest cluster galaxy. https://doi.org/10.1093/mnras%2Fstx920

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