科研之友
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摘要
We report the discovery of RG1M0150, a massive, recently quenched galaxy at z = 2.636 that is multiply imaged by the cluster MACSJ0150.3-1005. We derive a stellar mass of log M-* = 11.49(-0.16)(+0.10) and a half-light radius of R-e,R-maj = 1.8 +/- 0.4 kpc. Taking advantage of the lensing magnification, we are able to spatially resolve a remarkably massive yet compact quiescent galaxy at z > 2 in ground-based near-infrared spectroscopic observations using Magellan/FIRE and Keck/MOSFIRE. We find no gradient in the strength of the Balmer absorption lines over 0.6R(e)-1.6R(e), which are consistent with an age of 760 Myr. Gas emission in [N II] broadly traces the spatial distribution of the stars and is coupled with weak H alpha emission (log [N II]/H alpha = 0.6 +/- 0.2), indicating that OB stars are not the primary ionizing source. The velocity dispersion within the effective radius is sigma(e,stars) = 271 +/- 41 km s(-1). We detect rotation in the stellar absorption lines for the first time beyond z similar to 1. Using a two-integral Jeans model that accounts for observational effects, we measure a dynamical mass of log M-dyn = 11.24 +/- 0.14 and V/sigma = 0.70 +/- 0.21. This is a high degree of rotation considering the modest observed ellipticity of 0.12 +/- 0.08, but it is consistent with predictions from dissipational merger simulations that produce compact remnants. The mass of RG1M0150 implies that it is likely to become a slowly rotating elliptical. If it is typical, this suggests that the progenitors of massive ellipticals retain significant net angular momentum after quenching which later declines, perhaps through accretion of satellites.
- 出版日期2015-11-1
