Multi-phase carbon structure and dynamics in NGC 6334: Insights from CO, [C I], and [C II]

We present high-angular and velocity resolution observations of the emission lines of [CII] at 158 micron, [CI] at 609 micron, and the 12CO and 13CO (J=3-2) transitions toward the central region of NGC 6334, providing a detailed multi-phase view of carbon in this massive star-forming complex. By combining morphology and spatial scales information, kinematics, line profiles, and line ratio analyses, we quantify the distribution and physical state of ionized and atomic carbon, and carbon in its molecular form in CO. [CII] emission is the most extended, permeates the mapped region and is dynamically complex, while 13CO is compact and quiescent, and 12CO and [CI] occupy intermediate regimes connecting dense regions to transitional diffuse layers. We interpret these emission distributions such that the brightest [CII] emission traces photodissociation regions (PDRs) close to the H II region bubbles located along the central filament, while the extended [CII] emission arises from the more diffuse warm gas, indicating either cloud formation or dispersal processes. Remarkably, the [CI] is more extended than the 13CO, but less than [CII] and may probe the gas velocity structure resulting from colliding flows or cloud-cloud collisions. Line ratios involving [CII], such as [CII]/[CI] or [CII]/CO are systematically high, revealing widespread diffuse emission and localized UV-illuminated surfaces. Line ratio analysis and K-means clustering of [CI]/13CO versus dust continuum (cold 870 micron and warm 70 micron) emission reveal stratified chemical structure that UV photons penetrate deeply into the clumpy ridge (Av~18), suggesting a porous PDR. These results together depict that NGC 6334 is a clumpy, feedback-dominated PDR ridge with coexisting carbon phases, where [CI] and [CII] also trace dynamical processing through multiple velocity components linked to cloud-cloud collisions.