1. PROJECT OVERVIEW Include an explanation (in a few sentences) how the science goals in the proposal will be achieved through the data analysis plans. We propose to test the common and plausible, but empirically unsupported assumption that black hole accretion in luminous quasars is triggered by major, gas-rich mergers. We have already shown with the aid of ACS imaging that at recent times, since z1, there is no evidence for triggering of nuclear activity being dominated by merging. Crucially, with the arrival of WFC3, such a test has now also become possible at the peak of black-hole growth (at z2), where the mode of accretion may well be different and, indeed, related to merger events. We will obtain WFC3/IR SNAPshot observations of ~45 high-mass quasars at z2 with luminosities that dominate the luminosity function and, hence, super-massive black-hole growth. Careful subtraction of nuclear point source contributions will allow us to the morphological properties of the host galaxies and identify merger signatures. The inferred major-merger fraction will then be compared to the major merger fraction in a sample of 150 galaxies without active nucleus, but that are similar in mass and redshift, and analyzed in a fully analogous manner. This comparison sample will be constructed from the currently ongoing and already partially completed multi-cycle treasury program CANDELS. From the sample sizes and the demonstrated ability to identify major mergers in WFC3 imaging even in the presence of a dominating nuclear light source it follows that we will determine at the 95% confidence level whether luminous quasars have an increased merger fraction by at least a factor two and, hence, whether at z2 major mergers play a significant role in super-massive black-hole accretion.
|Effective start/end date||12/1/12 → 11/30/14|
- National Aeronautics Space Administration (NASA): $69,353.00