Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content

Jorge Moreno; Paul Torrey; Sara L. Ellison; David R. Patton; Phillip F. Hopkins; Michael Bueno; Christopher C. Hayward; Desika Narayanan; Dusan Keres; Asa A. F. Bluck; Lars Hernquist

doi:10.1093/mnras/stz417

arXiv · 1902.02305

Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content

Jorge Moreno·Paul Torrey·Sara L. Ellison·David R. Patton·Phillip F. Hopkins·Michael Bueno·Christopher C. Hayward·Desika Narayanan·Dusan Keres·Asa A. F. Bluck·Lars Hernquist

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Abstract

We present a comprehensive suite of high-resolution (parsec-scale), idealised (non-cosmological) galaxy merger simulations (24 runs, stellar mass ratio ~2.5:1) to investigate the connection between interaction-induced star formation and the evolution of the interstellar medium (ISM) in various temperature-density regimes. We use the GIZMO code and the second version of the 'Feedback in Realistic Environments' model (FIRE-2), which captures the multi-phase structure of the ISM. Our simulations are designed to represent galaxy mergers in the local Universe. In this work, we focus on the 'galaxy-pair period' between first and second pericentric passage. We split the ISM into four regimes: hot, warm, cool and cold-dense, motivated by the hot, ionised, atomic and molecular gas phases observed in real galaxies. We find that, on average, interactions enhance the star formation rate of the pair (~30%, merger-suite sample average) and elevate their cold-dense gas content (~18%). This is accompanied by a decrease in warm gas (~11%), a negligible change in cool gas (~4% increase), and a substantial increase in hot gas (~400%). The amount of cold-dense gas with densities above 1000 cm^3 (the cold ultra-dense regime) is elevated significantly (~240%), but only accounts for 0.15% (on average) of the cold-dense gas budget.

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Jorge Moreno, Paul Torrey, Sara L. Ellison, David R. Patton, Phillip F. Hopkins, Michael Bueno, Christopher C. Hayward, Desika Narayanan, Dusan Keres, Asa A. F. Bluck, Lars Hernquist. 2019-02-06. Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content. https://doi.org/10.1093/mnras%2Fstz417

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