Kinematics of z ≥ 6 galaxies from [C II] line emission

Journal
Date Issued
2019
Author(s)
Kohandel, M.
•
Pallottini, A.
•
Ferrara, A.
•
•
Behrens, C.
•
Carniani, S.
•
Gallerani, S.
•
DOI
Abstract
We study the kinematical properties of galaxies in the Epoch of Reionization via the [C II]158 μm line emission. The line profile provides information on the kinematics as well as structural properties such as the presence of a disc and satellites. To understand how these properties are encoded in the line profile, first we develop analytical models from which we identify disc inclination and gas turbulent motions as the key parameters affecting the line profile. To gain further insights, we use `Althæa', a highly resolved (30 pc) simulated prototypical Lyman-break galaxy, in the redshift range z = 6-7, when the galaxy is in a very active assembling phase. Based on morphology, we select three main dynamical stages: (I) merger, (II) spiral disc, and (III) disturbed disc. We identify spectral signatures of merger events, spiral arms, and extra-planar flows in (I), (II), and (III), respectively. We derive a generalized dynamical mass versus [C II]-line FWHM relation. If precise information on the galaxy inclination is (not) available, the returned mass estimate is accurate within a factor 2 (4). A Tully-Fisher relation is found for the observed high-z galaxies, i.e. L[C II] ∝ (FWHM)1.80 ± 0.35 for which we provide a simple, physically based interpretation. Finally, we perform mock ALMA simulations to check the detectability of [C II]. When seen face-on, Althæa is always detected at >5σ; in the edge-on case it remains undetected because the larger intrinsic FWHM pushes the line peak flux below detection limit. This suggests that some of the reported non-detections might be due to inclination effects.
Volume
487
Issue
3
Start page
3007
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2019MNRAS.487.3007K
Rights
open.access
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