A Massive Quiescent Galaxy Confirmed in a Protocluster at z = 3.09
A Massive Quiescent Galaxy Confirmed in a Protocluster at z = 3.09
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DOI：
10.3847/1538-4357/ac0cf8
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发表时间：
2021-06
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通讯作者：
M. Kubo;H. Umehata;Y. Matsuda;M. Kajisawa;C. Steidel;Toru Yamada;I. Tanaka;B. Hatsukade;Y. Tamura;K. Nakanishi;K. Kohno;Kianhong Lee;K. Matsuda
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作者：
M. Kubo;H. Umehata;Y. Matsuda;M. Kajisawa;C. Steidel;Toru Yamada;I. Tanaka;B. Hatsukade;Y. Tamura;K. Nakanishi;K. Kohno;Kianhong Lee;K. Matsuda
我们报告了一个巨大的静止星系，zspec=3.0922−0.004+0.008，在SSA 22视场的原星系团中，用凯克I望远镜的红外探测多目标光谱仪检测到巴耳末和Ca ii的吸收特征，光谱证实了这一点。这是迄今为止在原星团中确认的最遥远的静止星系。我们同时拟合光学到中红外光度学和光谱，用光谱能量分布（SED）模型的参数和非参数星星形成历史（SFHS）。这两个模型都很好地拟合了观测到的SED，并证实该天体是一个大质量的静止星系，恒星质量log（M/M）=11.26−0.04+0.03和11.54−0.00+0.03，参数和非参数模型的星星形成率分别为SFR/M yr−1 < 0.3和=0.01−0.01+0.03。前者的SFH被描述为一个瞬时的星爆，而后者的模型是更长的寿命，但这两个模型都同意突然淬火的星星形成在20.6 Gyr前。这个巨大的静止星系在一个极其密集的星系群中得到了证实，该星系群被预测为宇宙学数值模拟中通过多次合并形成的最亮星系团的祖先。我们发现了三个新的合理的[O iii]λ5007发射器在3.0791 ≤ z spec ≤ 3.0833附近的目标偶然发现。其中两个就在目标和它最近的大质量星系之间，可能是它们相互作用的证据。他们提出了未来的大规模和恒星质量的演变，这个巨大的静止星系通过合并。
We report a massive quiescent galaxy at zspec=3.0922−0.004+0.008 spectroscopically confirmed at a protocluster in the SSA22 field by detecting the Balmer and Ca ii absorption features with the multi-object spectrometer for infrared exploration on the Keck I telescope. This is the most distant quiescent galaxy confirmed in a protocluster to date. We fit the optical to mid-infrared photometry and spectrum simultaneously with spectral energy distribution (SED) models of parametric and nonparametric star formation histories (SFHs). Both models fit the observed SED well and confirm that this object is a massive quiescent galaxy with a stellar mass of log(M⋆/M⊙)=11.26−0.04+0.03 and 11.54−0.00+0.03 , and a star formation rate of SFR/M ⊙ yr−1 < 0.3 and =0.01−0.01+0.03 for parametric and nonparametric models, respectively. The SFH from the former modeling is described as an instantaneous starburst whereas that of the latter modeling is longer-lived, but both models agree with a sudden quenching of the star formation at ∼0.6 Gyr ago. This massive quiescent galaxy is confirmed in an extremely dense group of galaxies predicted as a progenitor of a brightest cluster galaxy formed via multiple mergers in cosmological numerical simulations. We discover three new plausible [O iii]λ5007 emitters at 3.0791 ≤ z spec ≤ 3.0833 serendipitously detected around the target. Two of them just between the target and its nearest massive galaxy are possible evidence of their interactions. They suggest the future great size and stellar mass evolution of this massive quiescent galaxy via mergers.