The bar-driven central complex of NGC 6946: A panchromatic and spatially resolved view of its star formation history and interstellar medium

Abstract

We present a detailed multi-wavelength analysis of the nearby spiral galaxy NGC 6946, combining optical integral field spectroscopy (GCMS), infrared ( ), and radio observations (THINGS and HERACLES). Herschel We aim to characterise both the integrated and spatially resolved properties of the stellar populations and interstellar medium (ISM), and to interpret them in the context of bar-driven galaxy evolution. We used the spectral energy distribution fitting code to derive stellar population properties (stellar mass, star formation history), and different prescriptions to derive ISM properties including atomic and molecular gas masses and the dust mass, dust temperature, and dust emissivity index, combining optical, infrared, and radio datasets. SINOPSIS 25 ) hosts sim40% of the stellar mass, as well as the bulk of the molecular gas and dust, and has sustained enhanced star formation over cosmic time. A major star formation episode occurred ∼ 0.6 Gyr ago. The spatially resolved Kennicutt--Schmidt relation shows that molecular gas alone explains only part of the current SFR variance, while alternative prescriptions incorporating stellar mass and dynamical equilibrium pressure yield only modest improvements. We also find radial enhancements in the effective oxygen yield, Y_ eff , and gas mass fraction, μ, relative to surrounding regions, consistent with sustained gas accumulation. Together with the molecular gas streaming motions previously detected in CO and Hα kinematic studies, our results are consistent with, and provide independent support for, the inward transport of gas driven by a system of nested bars. Our results are consistent with a scenario in which a recent episode of bar-driven gas inflow enhanced the central molecular gas reservoir and sustained elevated star formation, further supported by the elevated gas-to-dust ratio in the inner region, and the low global M_ HI /M_ H _2 ratio. These findings point to efficient HI-to-H_2 conversion, likely promoted by the combined effect of the secondary bar and the large dust content, ultimately regulating star formation. We also find indications consistent with a young stellar bar, given by the presence of a low-mass pseudo-bulge. The current decline in star formation despite large gas reservoirs suggests recent bar-driven quenching.