The History of Metal Production and Loss in the M31 Disk

Energetic feedback that drives gaseous outflows and redistributes matter is essential to shaping galaxies, but precisely how feedback couples to the gas remains poorly understood. In this work, we leverage missing metals as tracers of past gas flows to constrain the history of metal ejection and redistribution in M31. This nearby, roughly L∗ galaxy is a unique case where spatially resolved measurements of the gas-phase and stellar metallicity, dust extinction, and neutral ISM gas content are available, enabling a census of the metal mass present in stars, gas, and dust. We combine spatially resolved star formation histories from the Panchromatic Hubble Andromeda Treasury survey with a model of metal production by Type II SNe, Type Ia SNe, and AGB stars to calculate the history of metal production. We find that 62% of the metals formed in the M31 disk (between 1 < r < 20 kpc) are missing. We then use the metal production histories to place constraints on the timing of this metal loss and on the required redistribution of newly produced metals within the disk in the last ~2 Gyr.

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