文章基本信息

标题：Extended ionised and clumpy gas in a normal galaxy at z = 7.1 revealed by ALMA
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作者：S. Carniani ; S. Carniani ; R. Maiolino 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2017
卷号：605
页码：1-13
DOI：10.1051/0004-6361/201630366
语种：English
出版社：EDP Sciences
摘要：We present new ALMA observations of the [O iii]88 μm line and high angular resolution observations of the [C ii]158 μm line in a normal star forming galaxy at z = 7.1. Previous [C ii] observations of this galaxy had detected [C ii] emission consistent with the Lyα redshift but spatially slightly offset relative to the optical (UV-rest frame) emission. The new [C ii] observations reveal that the [C ii] emission is partly clumpy and partly diffuse on scales larger than about 1 kpc. [O iii] emission is also detected at high significance, offset relative to the optical counterpart in the same direction as the [C ii] clumps, but mostly not overlapping with the bulk of the [C ii] emission. The offset between different emission components (optical/UV and different far-IR tracers) is similar to that which is observed in much more powerful starbursts at high redshift. We show that the [O iii] emitting clump cannot be explained in terms of diffuse gas excited by the UV radiation emitted by the optical galaxy, but it requires excitation by in-situ (slightly dust obscured) star formation, at a rate of about 7 M⊙ yr-1. Within 20 kpc from the optical galaxy the ALMA data reveal two additional [O iii] emitting systems, which must be star forming companions. We discuss that the complex properties revealed by ALMA in the z ~ 7.1 galaxy are consistent with expectations by recent models and cosmological simulations, in which differential dust extinction, differential excitation and different metal enrichment levels, associated with different subsystems assembling a galaxy, are responsible for the various appearance of the system when observed with distinct tracers.
关键词：engalaxies: evolutiongalaxies: ISMgalaxies: high-redshiftinfrared: general