Short-lived star-forming giant clumps in cosmological simulations of z~2 disks

TL;DR

This paper uses high-resolution cosmological simulations with stellar feedback to study the formation, evolution, and disruption of giant star-forming clumps in z~2 galaxy disks, challenging previous migration models.

Contribution

It demonstrates that strong galactic winds cause short-lived clumps that do not migrate inward, aligning simulations with recent observational data on high-redshift galaxy clumps.

Findings

Giant clumps form in-situ via gravitational instabilities.

Winds disrupt clumps before they virialize or migrate inward.

Simulations reproduce observed clump ages and kinematics.

Abstract

Many observed massive star-forming z\approx2 galaxies are large disks that exhibit irregular morphologies, with \sim1kpc, \sim10^(8-10)Msun clumps. We present the largest sample to date of high-resolution cosmological SPH simulations that zoom-in on the formation of individual M*\sim10^(10.5)Msun galaxies in \sim10^(12)Msun halos at z\approx2. Our code includes strong stellar feedback parameterized as momentum-driven galactic winds. This model reproduces many characteristic features of this observed class of galaxies, such as their clumpy morphologies, smooth and monotonic velocity gradients, high gas fractions (f_g\sim50%) and high specific star-formation rates (\gtrsim1Gyr^(-1)). In accord with recent models, giant clumps (Mclump\sim(5x10^8-10^9)Msun) form in-situ via gravitational instabilities. However, the galactic winds are critical for their subsequent evolution. The giant clumps we obtain are short-lived and are disrupted by wind-driven mass loss. They do not virialise or migrate to the galaxy centers as suggested in recent work neglecting strong winds. By phenomenologically implementing the winds that are observed from high-redshift galaxies and in particular from individual clumps, our simulations reproduce well new observational constraints on clump kinematics and clump ages. In particular, the observation that older clumps appear closer to their galaxy centers is reproduced in our simulations, as a result of inside-out formation of the disks rather than inward clump migration.