Quenching Massive Galaxies with On-the-fly Feedback in Cosmological Hydrodynamic Simulations

TL;DR

This study implements on-the-fly feedback mechanisms in cosmological simulations to understand galaxy quenching, finding continuous thermal energy injection into hot halos effectively reproduces observed red galaxy populations.

Contribution

Introduces heuristic feedback prescriptions in simulations and demonstrates that continuous heating of hot halos is key to quenching massive galaxies effectively.

Findings

Merger-driven quenching alone does not sustain red sequence.

Continuous thermal energy injection reproduces observed luminosity functions.

Discrepancies suggest underestimation of metal retention and intermittent heating effects.

Abstract

Massive galaxies today typically are not forming stars despite being surrounded by hot gaseous halos with short central cooling times. This likely owes to some form of "quenching feedback" such as merger-driven quasar activity or radio jets emerging from central black holes. Here we implement heuristic prescriptions for these phenomena on-the-fly within cosmological hydrodynamic simulations. We constrain them by comparing to observed luminosity functions and color-magnitude diagrams from SDSS. We find that quenching from mergers alone does not produce a realistic red sequence, because 1 - 2 Gyr after a merger the remnant accretes new fuel and star formation reignites. In contrast, quenching by continuously adding thermal energy to hot gaseous halos quantitatively matches the red galaxy luminosity function and produces a reasonable red sequence. Small discrepancies remain - a shallow red sequence slope suggests that our models underestimate metal production or retention in massive red galaxies, while a deficit of massive blue galaxies may reflect the fact that observed heating is intermittent rather than continuous. Overall, injection of energy into hot halo gas appears to be a necessary and sufficient condition to broadly produce red and dead massive galaxies as observed.