Rest-Frame Ultraviolet to Near Infrared Observations of an Interacting Lyman Break Galaxy at z = 4.42

TL;DR

This study analyzes a high-redshift interacting galaxy system at z=4.42, combining spectral energy distribution fitting and hydrodynamical simulations to understand its evolution into a quasar and spheroid, supporting merger-driven galaxy formation models.

Contribution

It provides the first detailed spectral and morphological analysis of a z=4.42 merging galaxy system, linking observations with simulations to predict its future evolution.

Findings

System is the highest redshift merging galaxy with resolved tidal features.

Predicted evolution into a quasar by z~3.5 and a compact spheroid by z~2.5.

Supports merger-driven models of spheroid and black hole formation at high redshift.

Abstract

We present the rest-frame ultraviolet through near infrared spectral energy distribution for an interacting Lyman break galaxy at a redshift z=4.42, the highest redshift merging system known with clearly resolved tidal features. The two objects in this system - HDF-G4 and its previously unidentified companion - are both B_{435} band dropouts, have similar V_{606}-i_{775} and i_{775}-z_{850} colors, and are separated by 1", which at z=4.42 corresponds to 7 kpc projected nuclear separation; all indicative of an interacting system. Fits to stellar population models indicate a stellar mass of M_\star = 2.6\times 10^{10} M_\odot, age of \tau_\star = 720 My, and exponential star formation history with an e-folding time \tau_0 = 440 My. Using these derived stellar populations as constraints, we model the HDF-G4 system using hydrodynamical simulations, and find that it will likely evolve into a quasar by z\sim3.5, and a quiescent, compact spheroid by z\sim 2.5 similar to those observed at z > 2. And, the existence of such an object supports galaxy formation models in which major mergers drive the high redshift buildup of spheroids and black holes.