Extended ionised and clumpy gas in a normal galaxy at z = 7.1 revealed by ALMA

Journal
Date Issued
2017
Author(s)
Carniani, S.
•
Maiolino, R.
•
Pallottini, A.
•
•
•
Ferrara, A.
•
•
•
•
Gallerani, S.
•
•
Wagg, J.
•
DOI
Abstract
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.
Volume
605
Start page
A42
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2017A&A...605A..42C
Rights
open.access
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