Affiliation: University of Valencia

Contribution: Oral

Title: Galaxy Assembly in the Early Universe from NIRSpec/IFU Observations of ALMA/REBELS Galaxies

Abstract: The discovery enabled by JWST observations of numerous bright galaxies at Cosmic Dawn, along with the identification of potentially “Universe-breaking” massive galaxies, is reshaping our understanding of galaxy formation, and raise questions about how rapidly galaxies assembled their mass in the early Universe. In parallel with studies focusing on the characterization of the most distant sources, significant progress in understanding early galaxy formation can be achieved by studying the brightest and most massive galaxies that populated the Universe 200-400 million years later, likely the most immediate descendants of the intriguing objects observed at z>10. In this talk, we will present results based on a recent NIRSpec IFU R100 program targeting 12 exceptionally high-mass galaxies from the ALMA/REBELS sample, dating back to approximately 750 million years after the Big Bang (6.5 < z < 8.5). Leveraging the JWST’s high spatial and spectral resolution across a wide wavelength range, from the rest-frame UV to rest-frame optical, we can reconstruct spatially-resolved maps of their stellar and gas content. This allows us to derive spatially-resolved maps of stellar mass, star-formation rates, metallicity, ionizing radiation, and dust attenuation, among other parameters, which can be interpreted in terms of in-situ mass assembly, merger-driven star formation, and star-formation history (SFH). Remarkably, this sample also benefits from [CII]158𝜇m and dust continuum estimates from the recent ALMA large program REBELS, making this sample a unique laboratory to understand galaxy formation. Specifically the dust and gas mass estimates enabled by the ALMA observations combined with the gas-phase metallicity from the JWST spectra enable us to empirically constrain their global SFH, minimizing the dependence on modeling assumptions. These results will ultimately allow us to assess the star formation efficiency in massive galaxies at early epochs. The resulting combination of JWST and ALMA dataset will establish a reference sample of reionization epoch galaxies with unique panchromatic information for the JWST era and beyond.

This contribution can be found here (pdf).