Pushing the Atacama Large Millimeter/submillimeter Array to the Limit: 140 pc Resolution Observations of a z = 6.6 Quasar–Galaxy Merger Resolve Strikingly Different Morphologies of Dust Continuum and [C ii ] 158 μm Emission
Year: 2025
Type: article
Abstract: We present 0 . ″ 026 (140 pc) resolution Atacama Large Millimeter/submillimeter Array observations of [C ii] 158 μm and dust continuum emission of the z = 6.6 quasar J0305–3150, resolved over ∼300–400 independent resolution elements. The dust continuum emission is compact with ∼80% recovered within r < 0 . ″ 3 (1.6 kpc), whereas the [C ii] emission profile is composed of a central Gaussian ( r < 0 . ″ 4 , i.e., <2.2 kpc) and an extended component (detected up to ∼10 kpc at >3σ). We infer a direct contribution of the quasar to the observed 260 GHz continuum S ν,QSO/S ν,QSO + Host ≲ 1%. We report the detection of far-infrared (FIR)-detected star-forming clumps with r < 200 pc and properties similar to that of rest-frame UV–optical clumps reported in the literature. The 200 pc resolved [C ii]/FIR ratio follows the global relation with the FIR surface brightness established in low- and high-redshift galaxies, even at the quasar location. We find that dust continuum is emitted in regions of ∼ 0 ″ . 02 − 0 ″ . 04 consistent with the size of photodissociation regions (PDRs), whereas 50% of the [C ii] originates from larger physical scales (θ ≳ 2″). The large-scale [C ii] emission presents a velocity gradient aligned with a nearby companion with perturbed kinematics, and misaligned with the kinematics of the small-scale emission. The absence of significant [C ii] emission by structures with physical scale ≲ 1 kpc implies that [C ii] emission is not produced in dense PDRs located at the boundary of giant molecular clouds. We argue instead that [C ii] is produced in low-density PDRs in the interstellar medium and diffuse H i gas tidally stripped during the ongoing merger.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Award: G3816317015
OpenAlex ID: W4407045715