Oral Presentation
Star formation variability as a probe for the baryon cycle within galaxies
Presenter: Eun-jin Shin (Seoul National University)
We investigate the connection of the regulation of star formation and the cycling of baryons within and in and out of galaxies. We use idealized numerical simulations of Milky Way-mass galaxies, in which we vary the galaxy morphology and stellar feedback strength. By following individual gas parcels through the disk, spiral arms, and massive star-forming clumps, we quantify how gas moves through the different phases of the interstellar medium (ISM) and forms stars. We show that the residence time of gas in the dense ISM phase (tau_{SF}), the nature of spiral arms, and the clump properties depend on both the galaxy morphology and stellar feedback. We quantify signatures of the baryon cycle within galaxies using the temporal and spatial power spectrum density (PSD) of the star formation history (SFH). Stronger stellar feedback leads to more bursty star formation while the correlation timescale of the SFH is longer, because stronger feedback dissolves the dense ISM phase, leading to a more homogeneous ISM and a decrease in tau_{SF}. The bulge strength has a similar effect: the deep gravitational potential in a bulge-dominant galaxy imposes a strong shear force that breaks apart gas clumps in the ISM; this subsequently inhibits the fragmentation of gas and therefore the star formation in the disk, leading to a decrease in the spatial power on scales of ~ 1 kpc. We conclude that measurements of the temporal and spatial PSD of the SFH can provide constraints on the baryon cycle and the star formation process.
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