A Comprehensive Study of Nearby Galaxy Mergers with a Massive Integral-Field Spectroscopic Survey

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The important role played by collisions and mergers in galaxy evolution has been appreciated since the 1970's. Previous spectroscopic studies of colliding/merging galaxies, while confirming several basic predictions (e.g., elevated nuclear star formation and/or black hole accretion), generally explored only their brighter inner-most regions in a largely non-uniform manner. This research will use a wide-field integral field spectrometer (IFS) to measure the structure, kinematics, activity (star formation and/or black hole accretion), and chemical enrichment for approximately 1,300 local colliding/merging galaxies over their full visible extents. Identical observations of nearly 10,000 isolated galaxies of like masses will provide an essential "control" to reveal the full effects of collisions and mergers. This project will support one graduate and two undergraduate students, the latter tasked with building and implementing an IFS for a robotic student telescope.This research will first identify 1,300 interacting galaxies (early to late-stage mergers) from the larger SDSS-IV Mapping Nearby Galaxies at APO (MaNGA) IFS survey of 10,000 z 0.04 galaxies, the latter representing a 10-fold increase over previous such surveys. The team will then extract precise line and continuum measurements from the IFS data to determine each system’s structure and kinematics, the areal distribution of massive star formation and gas phase metallicity, as well as characterizing any nuclear activity (starburst and/or black hole accretion). A much larger sample of isolated galaxies from the MaNGA survey that are matched in mass will be analyzed in an identical manner to serve as a “control” to help isolate merger-induced from stochastic activity. From these data the team will derive estimates of the mass-dependent merger rates, the spatial extent of induced star formation and chemical enrichment, and the duty cycle and correlation of black hole accretion with merger state. This project touches on two science “frontier” questions from the Astro2010 Decadal Survey, namely, how do baryons cycle in and out of galaxies (and what do they do while they are there), and how do black holes grow and influence their surroundings? This work will support one graduate and two undergraduate students. The latter will build and write control/acquisition/reduction software for a medium-resolution IFS for the 0.5-m Iowa Robotic Telescope in Arizona. This instrument will contribute to active-learning spectroscopic astronomy labs at the University of Iowa.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.