Gaia Data Release 3. Exploring and mapping the diffuse interstellar band at 862 nm

Context. Diffuse interstellar bands (DIBs) are common absorption features in spectroscopic observations but their origins remain unclear. DIBs play an important role the life cycle of medium (ISM) and can also be used to trace Galactic structure. Aims. Here, we demonstrate capacity Gaia -Radial Velocity Spectrometer (RVS) DR3 reveal spatial distribution unknown molecular species responsible for most prominent DIB at 862 nm RVS passband, exploring ISM within a few kiloparsecs from Sun. Methods. The measured GSP-Spec module using Gaussian profile fit cool stars process hot stars. In addition equivalent widths uncertainties, provides characteristic central wavelength, width, quality flags. Results. We present extensive sample 476 117 individual measurements obtained homogeneous way covering entire sky. compare distributions carrier with reddening find evidence that carriers local bubble around Sun which contains nearly no dust. characterised width density 0.19 ± 0.04 Å kpc −1 scale height 98.60 −8.46 +11.10 pc. latter is smaller than dust height, indicating more concentrated towards plane. determine rest-frame wavelength unprecedented precision ( λ 0 = 8620.86 0.019 air) remarkable correspondence between velocities CO gas velocities, suggesting related macro-molecules. Conclusions. unique structure DIB.