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A Multi-frequency VLA continuum Investigation of Starburst and AGN activity in local U/LIRGs

Presentation #336.02D in the session Starburst Galaxies.

Published onJun 29, 2022
A Multi-frequency VLA continuum Investigation of Starburst and AGN activity in local U/LIRGs

Luminous and Ultra-luminous Infrared Galaxies (U/LIRGs) are rare types of extreme star-forming galaxies in the local Universe, yet they are the primary contributors to the infrared luminosity density at z ~ 2, when star formation was most active. Local U/LIRGs therefore provide the best opportunity to investigate in detail the extreme star-forming environments that may be ubiquitous at high-z. For my PhD dissertation, I use the Karl G. Jansky Very Large Array (VLA) to characterize the dust-obscured starburst and AGN (Active Galactic Nuclei) activity in a sample of 68 local U/LIRGs from the multi-wavelength Great Observatories All-sky LIRG Survey. Using ~100pc resolution 15 and 33 GHz continuum observations, I identify and characterize > 100 individual compact regions responsible for the energetics of these U/LIRGs. The individual star-forming regions identified in these U/LIRGs have up to 100 times higher star formation rates and 1000 times higher surface densities compared to those in nearby normal star-forming disk galaxies that are of similar sizes, and they rival lensed star-forming regions at z = 1-4. Further, we identify a sample of luminous galactic nuclei that are forming stars near the maximal capacity as predicted by theoretical models for star-forming disk supported by dust-reprocessed radiation pressure. Several of these nuclei have been identified to host AGN, and the rest may be going through a key phase of heavily obscured co-evolution between supermassive black holes and circumnuclear star formation that is thought to precede the formation of luminous quasars. Detection of high brightness temperature radio cores indicative of AGN activity via follow-up VLBI observations will directly verify this scenario. Lastly, the kpc scale 3–33 GHz radio spectral energy distribution and radio-IR correlation show large variation among the VLA-GOALS sample that reflects the various dominant energy source on resolved scales, which provide references for upcoming high-resolution exploration of dust-obscured activity in U/LIRGs with the next generation Very Large Array (ngVLA) and the James Webb Space Telescope (JWST).

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