Barry Rothberg (AIP)

The Janus Effect: How Multiple Stellar Populations Affect the Observed Dynamics of Major Mergers
When Dec 07, 2012 from 10:30 AM to 12:00 PM
  • Colloquium
Where SH, Lecture hall
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A key goal in astrophysics is the ability to identify the progenitors of present-day galaxies. Gas-rich major mergers in the local Universe, particularly Luminous and Ultraluminous Infrared Galaxies (LIRGs/ULIRGs) present a unique opportunity to study the formation of elliptical galaxies, including the most massive which will become QSO host galaxies. Yet, increasingly, a number of observational and theoretical studies suggest that both locally and afar, gas-rich mergers are not a major driving force in the formation of massive galaxies or responsible for the majority of star-formation at any given epoch. The ultimate implication is that Lambda-CDM cosmology and our current understanding of galaxy formation is incorrect.  Locally, this is driven by direct measurements of dynamical masses that show LIRGs/ULIRGs form only low-intermediate mass ellipticals.  I will present results which demonstrate that our understanding of the dynamical properties of major mergers in the local Universe relies not only upon instrumental resolution and our ability to collect photons, but on our ability to properly disentangle (and use to our advantage) the complicated nature of mergers.  The presence of multiple stellar populations and dust affects what we observe at different wavelengths, and until recently, has led to a major underestimation of the dynamical masses of LIRGs/ULIRGs by at least an order of magnitude. I will discuss these new and ongoing results in the context of the ULIRG-QSO connection, and whether this discrepancy is limited only to LIRGs/ULIRGs or if it affects our ability to measure the complete dynamical properties of all galaxies at all epochs.