Rings in Space -- from Collisional Ring Galaxies to Ultracompact Nuclear Rings

Dr. Marja Seidel (IPAC)
Tuesday, February 19, 2019 - 4:00pm

The plurality of galaxies in today’s Universe and their structure can give insight on their formation and evolution as well as on physical processes at play. In this talk I will discuss rings in galaxies: (i) Ring Galaxies, as gravitational probes of on-going collisions, (ii) Inner Rings, as chronometers for when the disks of massive galaxies settled into a dynamically cold state and (iii) Ultracompact Nuclear Rings as artefacts of the starburst-AGN connection. Using IMACS at the 6.5m Baade telescope at the Las Campanas Observatory, we are studying the kinematics of isolated ring galaxies, and comparing them with hydrodynamical N-body simulations of collisions between baryonic galaxies and pure dark-matter halos. The well-known Ring Galaxy, II Zw 28, will be discussed as one of our best candidates. Using MUSE at the VLT, we have determined the star formation history of inner rings as bar-built inner structures in nearby galaxies. This study is part of the TIMER Project to establish when galaxy disks settled into their currently cold state. Our results point to a lower limit of disk settling at around redshift 2, coinciding with the peak of cosmic star formation. Ultimately, the adaptive optics mode newly commissioned at the MUSE IFU has allowed us to study an ultracompact nuclear ring, leading to the discovery of a small 0.2'' (60 pc) radius kinematically decoupled core, as well as an outflow jet, in the archetypical AGN-starburst "composite" galaxy, NGC 7130. Studying these various aspects: the possible existence of pure dark matter halos, the settling of galaxy disks, and the immediate environment of AGNs, are each contributing to a better understanding of the evolution of galaxies in our universe.

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