Speaker
Description
Early-type galaxies (ETGs) are puzzling: cold molecular gas is detected in around a quarter of ETGs, however, they lack notable star formation to the extent that they are called 'red and dead' galaxies. Yet, many ETGs contain significant rotationally-supported gaseous disks. To probe the large-scale dynamics at play within local ETGs, we use the Toomre $𝑄$ ($Q_{T}$) stability criterion to study the large-scale gaseous dynamics and stability of seven early-type galaxies. We have high angular resolution data obtained as part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project with the Atacama Large Millimeter/submillimeter Array (ALMA). Using low-𝐽 CO transitions, and the modelling of stellar mass distributions with JamPy, we measure the Toomre $𝑄$ parameter across the inner $\approx 10^{2}$pc in these galaxies on spatial scales ranging from 60 to 120 pc. $Q_{T}$ is $\sim1$ dex higher in this sample of galaxies than $Q_{T}$ previously measured in late-type galaxies. The molecular gas surface density, and effective width respectively, both anti-correlate with $Q_{T}$, implying that regions with a lower gas density and lower gas turbulence are more gravitationally stable, therefore, little to no star formation. These results are consistent with a highly stable disk and provide an intuitive explanation for the high molecular gas surface densities, yet low star formation rates seen within ETGs.
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