Galaxies and massive black holes at z > 3
From the ground, observations of the rest-frame optical light of galaxies are limited to z < 3.5. The James Webb Space Telescope (JWST), launched in December 2021, has opened up access to rest-frame UV-to-optical emission of the most distant galaxies. On board James Webb, especially the NIRSpec Integral-Field Unit (IFU) with a 3”x3” field of view enables detailed perspectives on the galaxy population during the first 2 billion years of cosmic history. The Guaranteed Time Observations (GTO) survey GA-NIFS (Galaxy Assembly with NIRSpec-IFS) observes 55 galaxies at 2 < z < 11 to map their star-forming regions, kinematics including outflows, distribution of chemical elements, stellar populations, and ionization sources, such as massive black holes. We are also executing several open-time programs with NIRSpec IFU, including the Large Program BlackTHUNDER (Black holes in the early Universe and their dense surroundings) targeting the host galaxies of broad-line AGN at z > 5, to unveil the nature and impact of the first population of accreting black holes onto their host galaxies and immediate surroundings. With our data, we can estimate the masses of these distant black holes through scaling relations. In the future, we will be able to test these estimates with GRAVITY+.
Complementary to this, we are obtaining observations with IRAM/NOEMA to trace the molecular gas content of the host galaxies of some of these early AGN, while the CRISTAL program probes cold gas phases of typical star-forming galaxies during the same cosmic epoch.
Some highlights from our NIRSpec-IFS programs are listed below.
We found the first massive black hole triplet at high redshift:
https://ui.adsabs.harvard.edu/abs/2025arXiv250921575U/abstract
We revealed evidence for gas inflows and AGN feedback in the massive z ~ 4 galaxy GN20:
https://ui.adsabs.harvard.edu/abs/2024MNRAS.533.4287U/abstract
We found a massive black hole pair just 740 million years after the Big Bang:
https://ui.adsabs.harvard.edu/abs/2024MNRAS.531..355U/abstract. One black hole was discovered through the rapid motions of gas within its sphere of influence, while the other black hole was revealed through its ionizing radiation (see also https://ui.adsabs.harvard.edu/abs/2024A%26A...691A.345M/abstract).
We discovered the first moderate-luminosity over-massive black hole in a galaxy 1 billion years after the Big Bang: https://ui.adsabs.harvard.edu/abs/2023A%26A...677A.145U/abstract. The interstellar medium in the host galaxy is chemically stratified, with the densest regions being strongly enhanced in nitrogen: https://ui.adsabs.harvard.edu/abs/2024MNRAS.535..881J/abstract.
