Rest-Frame Ultraviolet to Near-Infrared Observations of an Interacting Lyman Break Galaxy at z=4.42
Shapley, Alice E.; Hernquist, Lars; Fazio, Giovanni G.; Cox, Thomas J.; Hopkins, Philip F.; Lin, Lihwai; Younger, Joshua D.; Huang, Jia-Sheng; Simard, Luc; Lai, Kamson; Kereš, Dušan; Papovich, Casey J.; Cheng, Yi-Wen; Yan, Haojin
United States, Germany, Canada, Taiwan
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 B435-band dropouts, have similar V606-i775 and i775-z850 colors, and are separated by 1", which at z=4.42 corresponds to 7 kpc projected nuclear separation; these are all indicators of an interacting system. Fits to stellar population models indicate a stellar mass of M*=2.6×1010 Msolar, an age of τ*=720 Myr, and an exponential star formation history, with an e-folding time τ0=440 Myr. 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~3.5, and a quiescent, compact spheroid by z~2.5, similar to those observed at z>~2. The existence of such an object supports galaxy formation models in which major mergers drive the high-redshift buildup of spheroids and black holes.