The fate of the interstellar medium in early-type galaxies

Context. Removing the cold interstellar medium (ISM) from a galaxy is essential to quenching star formation, however, the exact mechanism behind this process remains unclear. Aims. The objective of this work is to find the mechanism responsible for dust and gas removal in simulated early-type galaxies. Methods. We studied a statistically significant sample of massive (M* > 1010 M⊙), simulated early-type galaxies in a redshift range of 0.02−0.32 in the context of its ISM properties. In particular, we investigated the cold dust and gas removal timescales, the cold gas inflows, and their relation with black hole mass. We also investigated the evolution of galaxies in the dust mass and star formation rate (SFR) plane and the influence of merger events. Finally, we broke down the dust destruction mechanisms to find which (if any) of the implemented processes dominate as a function of a galaxy’s stellar age. Results. We find a good agreement with previous observational works dealing with the timescales of dust and HI removal from early-type galaxies. When considering the dust-to-stellar-mass ratio as a function of time in simulations, we recovered a similar decline as in the observational sample as a function of stellar age, validating its use for timing the ISM decline. Moreover, we recovered the observed relation between dust mass and the SFR for actively star-forming galaxies, as well as that of passive early-type galaxies. We also show that starburst galaxies form their own sequence on the dust mass and SFR plot in the form of log(Mdust, SB) = 0.913 × log(SFR)+6.533, with a 2σ scatter of 0.32. Finally, we find that type II supernova reverse shocks dominate the dust destruction at the early stages of early-type galaxy evolution; however, we also see that at later times, stellar feedback becomes more important. We show that merger events lead to morphological transformations by increasing the bulge-to-total stellar mass ratio, followed by an increase in black hole masses. The black hole feedback resulting from radio mode accretion prevents the hot halo gas from cooling, indirectly leading to a decrease in the SFR.