[yt-dev] Issue #1079: Gadget velocities of gas cells not being read correctly? (or unit problem?) (yt_analysis/yt)

Anonymous issues-reply at bitbucket.org
Fri Sep 4 10:04:03 PDT 2015


New issue 1079: Gadget velocities of gas cells not being read correctly?  (or unit problem?)
https://bitbucket.org/yt_analysis/yt/issues/1079/gadget-velocities-of-gas-cells-not-being

Anonymous:

A recent update did something to drastically alter the gas cell velocities for gadget format files.  As an example, the test script here reads in the GadgetDiskGalaxy test simulation and creates a histogram of the z-velocity of all gas within 300 comoving kpc of the center of the galaxy.  The histogram shows both cells by ['gas','velocity_z'] and gas particles by the z-component of ['PartType0','Velocities'] (and also dark matter and star particles).  The cell velocities show a much narrower distribution than any of the particle types.

In addition, the script calculates the z-component of the center of mass velocity, comparing using cell-masses and cell-velocities to gas particle masses and velocities.  The two ways of computing it disagree by a factor of ~2.

Included is the script and the resulting histogram. 





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