Kat Barger UW-Madison

Title: Understanding the Evolution of the Magellanic System through Tidal Debris: Characterizing the Magellanic Bridge

Abstract: Galaxy interactions have greatly disturbed and redistributed the gas in the Magellanic System throughout the halos of the Milky Way and the Magellanic Clouds. In this talk, we will discuss a recent Hα emission-line survey of warm-ionized gas in the Magellanic Bridge using the Wisconsin Hα Mapper. This census allows us to investigate the density, kinematics, morphology, source of ionization, and fate of this tidal remnant. Determining the properties of tidal debris is key for understanding the evolution of these galaxies and other tidally disturbed systems.

Laura Blecha CfA

"Signatures of Supermassive Black Hole Mergers: Before and After"

Abstract: Supermassive black hole (SMBH) pairs are expected to form in major galaxy mergers. However, until recently, only a few such objects were known, and even less is known empirically about their subsequent evolution to a BH merger and gravitational-wave recoil kick. I will review the remarkable recent progress in identifying candidate SMBH pairs, as well as recent identifications of candidate recoiling SMBHs. I will then describe our efforts to interpret these findings and make predictions for future observations using hydrodynamic simulations of galaxy mergers that include SMBHs. Because many candidate SMBH pairs have been identified as double-peaked narrow-line (NL) AGN, which may be associated with BH motion on kiloparsec scales, we have made a first attempt to model the NL region in galaxy merger simulations. In general, we find that double-peaked NL AGN are a short-lived but generic phase in gaseous major mergers, and that they arise from a varied combination of BH motion and gas kinematics. I will discuss the implications of our findings for follow-up confirmation of SMBH pair candidates. Additionally, I will summarize the results of our large study of recoiling SMBHs in galaxy merger simulations. I will describe the dynamics of recoil in gas-rich versus gas-poor mergers, as well as the possible effects of recoil on star formation and the BH-bulge relations. Recoiling SMBHs may be observed as kinematically- or spatially-offset AGN with lifetimes of up to tens of Myr; I will conclude by describing efforts to model a candidate recoiling SMBH that displays both types of offset.