The formation of disks in massive spiral galaxies

TL;DR

This paper investigates how large spiral galaxy disks form, proposing that gas-rich major mergers rebuild disks, explaining observed galaxy evolution and kinematic anomalies over the past 6 billion years.

Contribution

It introduces the spiral-rebuilding scenario as a new mechanism for large disk formation in present-day spirals based on deep observations and modeling.

Findings

Half of distant spirals had anomalous kinematics 6 Gyr ago

Gas-rich major mergers can rebuild galaxy disks

Most star formation is linked to merging events

Abstract

The flatness of the rotation curve inside spiral galaxies is interpreted as the imprint of a halo of invisible matter. Using the deepest observations of distant galaxies, we have investigated how large disks could have been formed. Observations include spatially resolved kinematics, detailed morphologies and photometry from UV to mid-IR. Six Giga-years ago, half of the present-day spirals had anomalous kinematics and morphologies that considerably affect the scatter of the Tully Fisher relation. All anomalous galaxies can be modelled through gas-rich, major mergers that lead to a rebuilt of a new disk. The spiral-rebuilding scenario is proposed as a new channel to form large disks in present-day spirals and it accounts for all the observed evolutions since the last 6 Giga-years. A large fraction of the star formation is linked to merging events during their whole durations.