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SUMMARY:Beyond Diagnostic Diagrams: Spectral Decomposition of Ionizing Sou
 rces in MaNGA
DTSTART;VALUE=DATE-TIME:20261028T173500Z
DTEND;VALUE=DATE-TIME:20261028T174500Z
DTSTAMP;VALUE=DATE-TIME:20261028T044952Z
UID:indico-contribution-3636@nyx.physics.mcgill.ca
DESCRIPTION:Speakers: Aayushmathi Ashok (University of Victoria)\nStar for
 mation rates (SFR) and gas-phase metallicities in galaxies are usually mea
 sured from strong nebular emission lines under the assumption that young m
 assive stars are the only source ionizing the gas. In galaxies hosting an 
 active galactic nucleus (AGN)\, or containing old stellar populations\, ha
 rder radiation also produces these lines\, so the standard approach is to 
 classify each region with emission-line diagnostic diagrams and discard an
 ything not purely star-forming. In the MaNGA integral field spectroscopy s
 urvey\, more than half of the spatially resolved spectra (spaxels) passing
  our quality cuts fall outside the star-forming region. We apply a deep co
 nvolutional neural network that decomposes the full spectrum of each spaxe
 l into a star-forming and a non-star-forming component\, for roughly 740\,
 000 spaxels across 6\,500 galaxies\, and fit each decomposed component for
  both emission lines and continuum.\n\nThe decomposition can be used in tw
 o complementary ways. In star-forming regions\, it acts as a correction by
  removing any residual non-star-forming contamination. We use this techniq
 ue to reconstruct key galaxy scaling relations and find that the correctio
 ns are small. In composite and AGN-dominated regions\, it isolates any und
 erlying star formation. We confirm that H$\\alpha$-based SFR is substantia
 lly overestimated in AGN-classified spaxels\, and find that metallicity co
 rrections depend on the type of ionizing source. We demonstrate that this 
 decomposition can be used to extend classical calibrations to regions that
  are usually discarded in population-level studies\, and to further our un
 derstanding of how AGN activity connects to star formation and chemical en
 richment in galaxies.\n\nhttps://nyx.physics.mcgill.ca/event/587/contribut
 ions/3636/
LOCATION:Online 
URL:https://nyx.physics.mcgill.ca/event/587/contributions/3636/
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