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zhafen / linefinder

A tool for finding and classifying the worldlines of Lagrangian parcels of mass, in the context of hydrodynamic simulations of galaxy formation.
https://zhafen.github.io/linefinder
MIT License
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There may exist wind that is not classified as such #61

Closed zhafen closed 6 years ago

zhafen commented 7 years ago

Originally reported by Zachary Hafen (Bitbucket: zhafen, GitHub: zhafen)

If our snapshot resolution is too low we may miss wind that was spat out. An easy way to check if this is an issue is to look for any particles that meet the following conditions:

  1. They are not classified as wind.
  2. They have already been accreted onto the main galaxy.
  3. They are a large distance away from the main galaxy.
zhafen commented 6 years ago

Original comment by Zachary Hafen (Bitbucket: zhafen, GitHub: zhafen)

In our new definition, this wind is a very small fraction.

zhafen commented 6 years ago

Original comment by Zachary Hafen (Bitbucket: zhafen, GitHub: zhafen)

Yup, it can exist, and can be up to ~1% of the mass between 0.1-2 Rvir. Here's a video of it.

It seems like the majority of this material ends up misclassified through two steps:

  1. The particles end up just outside the galaxy but moving at a slow speed
  2. A wind or other strong effect moves the particles to outside 0.1 Rvir by z=0.25.

Case (1) can happen in a few ways. For example, the merger tree jumping around at high redshift can cause this to happen. It can also happen through turbulent motion in the galaxy that pushes gas to just outside 2Rhalf (the Rgal used for this plot). Regarding case (2), strong winds are very common at all redshifts, so seeing them blast tangential material to a large radius isn’t surprising. It also looks like there might be some tidal effect for some of the material that was just outside Rgal prior to z=0.25. Hard to say though.

The new galaxy definition we’re testing might help with some of this. There’s a simple fix for the rest of the material: any material that reaches sufficiently large radii, regardless of its radial velocity at the time of ejection, is classified as wind.

In any case, this is a small fraction of material, and unlike NEP stars, I don’t think this is a sign of a bigger issue in the pipeline, beyond what we’re already addressing.