Abstract:
The combined power of ALMA and JWST is rapidly transforming our view of galaxies in the first billion years. Over the past few years, JWST has been systematically identifying galaxies well beyond the Hubble redshift frontier at z>10, yielding important insights into their early metal enrichment and stellar mass build-up. At the same time, ALMA is providing a complementary perspective on the obscured star formation, dust, and gas contents of distant galaxies, helping to build a complete multi-wavelength picture.
In this talk, I will first show how ALMA observations reveal the widespread presence of dust as far back as z≈7-8, and how multi-band continuum observations are essential for reliable measurements of galaxy dust masses and star-formation rates at these epochs. I will then present recent JWST/NIRSpec observations of dusty galaxies in the epoch of reionization, and discuss the possible pathways through which they rapidly assembled their dust reservoirs.
Next, I will demonstrate how JWST spectroscopy of z>6 galaxies is key to interpreting their far-infrared line emission observed with ALMA. Emission lines such as [C II] 158 μm and [O III] 88 μm trace the cool and ionized phases of the interstellar medium, respectively, but their line ratios reveal physical conditions unlike those typically seen in the local Universe. I will explore the physical drivers behind the elevated [O III] 88 μm / [C II] 158 μm ratios seen at high redshift, and present new [O III] 88 μm detections of JWST-identified sources beyond z>8.5. Finally, I will highlight the exciting future prospects with the upcoming ALMA Cycle 12 Large Program PHOENIX, which will observe the [O III] 88 μm line and underlying dust continuum emission in a statistical sample of galaxies all the way out to z≈15.
