2024/02/14 by Nakazato, Yurina, Ceverino, Daniel, Yoshida, Naoki · 4 citations
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2402.08911
Recent JWST observations with superb angular resolution have revealed the existence of clumpy galaxies at high redshift through the detection of rest-frame optical emission lines. We use the FirstLight simulation to study the properties of (sub-)galactic clumps that are bright in [OIII] 5007\mathrm\mathringA line with flux greater than ∼ 10-18 \rm erg s-1 cm-2, to be detected by JWST. For 62 simulated galaxies that have stellar masses of (0.5-6) × 1010 M_\odot at z=5, we find clumps in 1828 snapshots in the redshift range z = 9.5-5.5. The clumps are identified by the surface density of star formation rate. About one-tenth of the snapshots show the existence of clumpy systems with two or more components. Most of the clumps are formed by mergers and can be characterized by their ages; central clumps dominated by stellar populations older than 50 Myr, and off-centered clumps dominated by younger stellar populations with specific star formation rates of ∼ 50 \rm Gyr-1. The latter type of young clumps is formed from gas debris in the tidal tails of major mergers with baryonic mass ratios of 1 ≤ q < 4. The merger-induced clumps are short-lived, and merge within a dynamical time of several tens million years. The number density of the clumpy systems is estimated to be ∼ 10-5 \rm cMpc-3, which is large enough to be detected in recent JWST surveys.