How HST/WFC3 and JWST can measure galaxy assembly and AGN growth

Rogier Windhorst, Seth H. Cohen

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Accretion disks around supermassive black holes (SMBH) in the centers of galaxies are the central engines of active galactic nuclei (AGN), which are observable over the entire electromagnetic spectrum and out to the beginning of galaxy formation. The gradual assembly of galaxies is believed to have resulted in SMBH today. The growth of SMBH is largely hidden by dust, and possibly by large time delays between galaxy mergers and the feeding of the central monster, so the connection between galaxy assembly and SMBH growth is currently at best circumstantial. Facilities like HSTWFC3 and the JamesWebb Space Telescope (JWST) are needed to trace this process from the epoch of reionization to the present. Using panchromatic deepHSTWFC3+ACS imaging data, grismspectra, and ground-based spectroscopy in GOODS and the Hubble Ultra Deep Field (HUDF), we address this issue through the epoch-dependent rate of major mergers in massive galaxies in the HUDF, and through SED-fitting of objects with and without (known) AGN in GOODS. On average, the field galaxy population at z = 1 - 6 has an underlying star-forming SED with typical ages of 0.1 - 0.2 Gyr. However, most AGNdominated objects at z = 0.5 - 1.5 have an underlying stellar SED age of ∼ 1 Gyr on average. This suggests that AGN growth and SMBH feeding may become visible 0.5 - 1 Gyr after the dynamical event which triggers the dominant starburst at these redshifts. This may also be reflected in the peak in the massive galaxy major merger rate compared to the peak in the redshift distribution of weak AGN. Finally, we discuss how JWST will expand on this topic in the next decade from the epoch of first light to the present.

Original languageEnglish (US)
Title of host publicationAIP Conference Proceedings
Number of pages9
Publication statusPublished - 2010
Event1st Stars and Galaxies: Challenges for the Next Decade - Austin, TX, United States
Duration: Mar 8 2010Mar 11 2010


Other1st Stars and Galaxies: Challenges for the Next Decade
CountryUnited States
CityAustin, TX



  • AGN growth
  • Galaxy assembly
  • Hubble WFC3
  • James Webb Space Telescope

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Windhorst, R., & Cohen, S. H. (2010). How HST/WFC3 and JWST can measure galaxy assembly and AGN growth. In AIP Conference Proceedings (Vol. 1294, pp. 225-233)