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Abstract We employ the Feedback In Realistic Environments (FIRE-2) physics model to study how the properties of giant molecular clouds (GMCs) evolve during galaxy mergers. We conduct a pixel-by-pixel analysis of molecular gas properties in both the simulated control galaxies and galaxy major mergers. The simulated GMC pixels in the control galaxies follow a similar trend in a diagram of velocity dispersion (σv) versus gas surface density (Σmol) to the one observed in local spiral galaxies in the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) survey. For GMC pixels in simulated mergers, we see a significant increase of a factor of 5–10 in both Σmolandσv, which puts these pixels above the trend of PHANGS galaxies in theσvversus Σmoldiagram. This deviation may indicate that GMCs in the simulated mergers are much less gravitationally bound compared with simulated control galaxies with virial parameters (αvir) reaching 10–100. Furthermore, we find that the increase inαvirhappens at the same time as the increase in global star formation rate, which suggests that stellar feedback is responsible for dispersing the gas. We also find that the gas depletion time is significantly lower for high-αvirGMCs during a starburst event. This is in contrast to the simple physical picture that low-αvirGMCs are easier to collapse and form stars on shorter depletion times. This might suggest that some other physical mechanisms besides self-gravity are helping the GMCs in starbursting mergers collapse and form stars.
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The SAMI galaxy survey: a range in S0 properties indicating multiple formation pathways
ABSTRACT It has been proposed that S0 galaxies are either fading spirals or the result of galaxy mergers. The relative contribution of each pathway and the environments in which they occur remain unknown. Here, we investigate stellar and gas kinematics of 219 S0s in the SAMI Survey to look for signs of multiple formation pathways occurring across the full range of environments. We identify a large range of rotational support in their stellar kinematics, which correspond to ranges in their physical structure. We find that pressure-supported S0s with v/σ below 0.5 tend to be more compact and feature misaligned stellar and gas components, suggesting an external origin for their gas. We postulate that these S0s are consistent with being formed through a merger process. Meanwhile, comparisons of ellipticity, stellar mass, and Sérsic index distributions with spiral galaxies show that the rotationally supported S0s with v/σ above 0.5 are more consistent with a faded spiral origin. In addition, a simulated merger pathway involving a compact elliptical and gas-rich satellite results in an S0 that lies within the pressure-supported group. We conclude that two S0 formation pathways are active, with mergers dominating in isolated galaxies and small groups, and the faded spiral pathway being most prominent in large groups ($$10^{13}\lt \rm {M_{halo}}\lt 10^{14}$$).
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- Award ID(s):
- 2009416
- PAR ID:
- 10265905
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 498
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 2372 to 2383
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/staa2417
