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We present a series of our studies on how HI is accreted, distributed and connected with the formation of optical structures in massive disk galaxies in the low redshift universe. First We introduce the Bluedisk project, an HI imaging survey with the aim of searching for signs of gas accretion in massive HI-excess disk galaxies. Major and minor merger events are ruled out as the main source of gas accretion. We found an HI-rich environment around HI-rich galaxies, out to a projected distance of 1 Mpc and systematic velocity difference of 500 km/s, supporting a scenario where the central galaxies are fuelled by an extended gas reservoir. We revisit the remarkably tight HI size-mass relation of galaxies. We find that the scatter around the relation does not depend on mass or HI richness of galaxies. We discuss its constrain on galaxy formation models. We show that the cold gas is closely connected with the formation of central bulges, bars, disks and disk outskirts in massive disk galaxies. |
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