Mapping gas accretion and stellar kinematics to sub-kiloparsec scales in NGC 4696 with JWST/NIRSpec

Abstract

We present JWST/NIRSpec IFU spectroscopy of the central $618\times 618$ pc${}^2$ ($\sim 3^{\prime \prime }\times 3^{\prime \prime }$) of NGC 4696, the BCG in the Centaurus cluster. Leveraging the $\sim 0.1^{\prime \prime }$ ($20.6$ pc) pixel size of JWST, we resolve a compact circumnuclear rotating disk (radius of $\sim 120$ pc) traced by Pa$\alpha$ and H${}_2$ 1$-$0 S(1) emission, which allows a reassessment of the AGN position based on the kinematic centre of this disk. A central Pa$\alpha$ velocity dispersion reaching $\sigma \sim 449$ km s${}^{-1}$ implies a SMBH mass of $\sim 10^9$ M${}_{\odot }$, corresponding to a sphere of influence of $r_{\inf }\sim 60$ pc, resolved by our observations. Position-velocity diagrams reveal an increase from $\sim -200$ to $\sim 600$ km s${}^{-1}$ on scales of $\sim 150$ pc (a gradient of $4.7$ km s${}^{-1}$ pc${}^{-1}$) and an accretion rate of $\sim 18$ M${}_{\odot }$ yr${}^{-1}$ feeding the CND. The Pa$\alpha$ emission shows a double-component in the core, with a high-dispersion redshifted component reaching $\sigma \sim 600$ km s${}^{-1}$. In contrast, MUSE H$\alpha$ observations covering the $\sim 10$ kpc-scale filamentary structure recover only weak velocity gradients ($\lesssim 150$ km s${}^{-1}$) within $\sim 300\times 300$ pc${}^2$ and do not resolve the disk due to larger PSFs and pixel sizes. ALMA CO(2-1) data reveal only compact molecular clumps within a $\sim 410\times 410$ pc${}^2$ region, with no extended counterpart to the structures traced by Pa$\alpha$ and H${}_2$ 1$-$0 S(1). Stellar kinematics show a smooth velocity field and broad dispersion profile, clearly decoupled from both the multiphase gas and the hot ICM probed by XRISM. These results provide a direct, spatially resolved view of gas dynamics within the inner few hundred parsecs, demonstrating the power of JWST/NIRSpec to probe SMBH feeding.

Submitted to ApJ and revised in response to referee comments (36 pages, 23 figures)