The disk-halo interface of the edge-on galaxy NGC891: discovery of a 1.3kpc thick molecular gas disk

The halos surrounding spiral galaxies act as a bridge between the galaxy and the IGM. It is therefore of paramount importance to gain a deeper knowledge of the nature and kinematics of this medium. They host most of the baryonic mass in the Universe, and many authors point to SF- or AGN-driven feedback as one of the main mechanisms regulating the presence of baryons outside the galactic disks. In this work, we aim to reveal the internal structure and kinematics of the molecular gas using data obtained with HERA, with the IRAM 30m, of the CO (2-1) emission of NGC891. This non-starburst/non-AGN galaxy, which is quite similar in size and structure to the Milky Way, is the perfect target to study the vertical structure of the molecular gas on "normal" SFG disks, and a unique opportunity to study the origin of the baryonic material in galactic halos and the feedback-driven mechanisms that regulate this process. The CO images were compared with the Hα and HI maps of the Galaxy to understand the possible correlation with the star formation feedback in the disk and the HI distribution. The best fit results for the molecular gas distribution confirm the existence of a thin and a thick molecular gas disk, where the thick disk extends up to 1.36 kpc above the galactic plane and may contain up to ∼25% of the total molecular mass reservoir. Dark dust columns appear to connect the inner disk to to the halo, suggesting supernova-driven outflows that expel the baryonic material.