The kiloparsec-scale gas kinematics in two star-forming galaxies at z ∼ 1.47 seen with ALMA and VLT-SINFONI

Molina, J; Ibar, Edo; Smail, I; Swinbank, AM; Villard, E; Escala, A; Sobral, D; Hughes, TM

Abstract

We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(J = 2 − 1) observations of two main-sequence star-forming galaxies at z ∼ 1.47 taken from the High-Z Emission Line Survey (HiZELS). These two systems have been previously reported to be molecular gas rich fH2≡MH2/(MH2+M⋆)∼0.8⁠. We carried out a follow-up study to resolve, at ∼kpc-scales, the CO emission. These new observations are combined with our earlier ALMA observations (sensitive to diffuse CO emission) and compared with our previous Hα-based study at matched spatial resolution. One target is marginally resolved in CO(2-1), showing complex dynamics with respect to the ionised gas traced by Hα. While the other source is spatially resolved, enabling a detailed exploration of its internal dynamical properties. In this system, both gaseous phases show similar spatial extension, rotation velocities and velocity dispersions (Vrot ∼ σv ∼ 100 km s−1) suggesting a rotational velocity to velocity dispersion ratio consistent with unity. By comparing the ionized and molecular gas tracers through the use of a two-dimensional kinematic model, we estimate a median depletion time τdep = 2.3 ± 1.2 Gyr for the galaxy as a whole. This value is in agreement with the average τdep value observed in local star-forming galaxies at similar spatial scales. Using a thick-disk dynamical modelling, we derive a dynamical mass Mdyn = (1.59 ± 0.19) × 1011 M⊙ within ≈6 kpc. This suggests a dark matter fraction (fDM ≡ MDM/Mdyn of 0.59 ± 0.10, in agreement with the average fDM value derived from stacked rotation curve analysis of galaxies at similar redshift range.

Citation

Molina, J., Ibar, E., Smail, I., Swinbank, A., Villard, E., Escala, A., …Hughes, T. (2019). The kiloparsec-scale gas kinematics in two star-forming galaxies at z ∼ 1.47 seen with ALMA and VLT-SINFONI. Monthly Notices of the Royal Astronomical Society, 487(4), 4856-4869. https://doi.org/10.1093/mnras/stz1643

• Journal Article Type: Article
• Acceptance Date: Jun 8, 2019
• Online Publication Date: Jun 13, 2019
• Publication Date: Aug 31, 2019
• Deposit Date: Jun 14, 2019
• Publicly Available Date: Jun 14, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 487
• Issue: 4
• Pages: 4856-4869
• DOI: https://doi.org/10.1093/mnras/stz1643
• Public URL: https://durham-repository.worktribe.com/output/1299702