[yt-users] yt.lagrangian_volume

Chen Jingjing chenjj235 at gmail.com
Tue Oct 28 12:00:44 PDT 2014


Hi,
I am using the code yt.lagrangian_volume to trace the box that contains the
dark matter particles at an early stage(higher redshift). But I was quite
confused about the output. I am attaching the output file below.
(1) I don't know what the values for the box in the new frame mean, i.e.
what is the unit of these values? It seems to be the normalized scale
because the values are about 1. But it does not seem to be normalized too
because there are some values that are larger than 1. Is that due to the
periodicity of the box?
(2) The bounding box and box in the new frame seems to have the same size.
The difference between the two box is just translation. But I was expecting
that the box should be expanding/collapsing.
(3) The COM (center of mass) in the output is within neither of the box.

Does anyone know how to explain the box values in the output file?

Thanks,
Jingjing

-- 

Jingjing Chen [ chenjj235 at gmail.com ]
Department of Astronomy
Columbia University
550 West 120th Street
New York, New York 10027
Cell Phone: +1(347)5746709
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Halo id: 172
The bounding box:
    2.46816151e-01 6.51687052e-01 3.26582290e-01
    1.34693109e+00 7.13922619e-01 4.11343260e-01

centered on COM location of halo in later pf:
    3.07192254e-01 6.10915166e-01 4.75784800e-01

which yields a boundary box in the new frame:
    4.39623896e-01 5.40771886e-01 3.50797490e-01
    1.53973884e+00 6.03007453e-01 4.35558460e-01

with a total bound volume of 5.80326803e-03
---------------------------------------------


Halo id: 207
The bounding box:
    5.14027270e-01 9.20059737e-01 3.01156090e-01
    7.14227863e-01 1.01232136e+00 3.55802598e-01

centered on COM location of halo in later pf:
    6.56417227e-01 5.32948505e-02 3.41362907e-01

which yields a boundary box in the new frame:
    3.57610043e-01 1.36676489e+00 4.59793183e-01
    5.57810637e-01 1.45902651e+00 5.14439691e-01

with a total bound volume of 1.00936646e-03
---------------------------------------------


Halo id: 273
The bounding box:
    4.74680791e-01 7.88664695e-01 9.26055230e-01
    7.53242012e-01 1.02076683e+00 1.09591055e+00

centered on COM location of halo in later pf:
    7.00702981e-01 5.30265432e-02 8.93324224e-01

which yields a boundary box in the new frame:
    2.73977811e-01 1.23563815e+00 5.32731005e-01
    5.52539031e-01 1.46774029e+00 7.02586324e-01

with a total bound volume of 1.09819368e-02
---------------------------------------------


Halo id: 307
The bounding box:
    3.42604019e-01 9.12806628e-01 9.25560570e-01
    1.43516969e+00 1.00537579e+00 9.86968578e-01

centered on COM location of halo in later pf:
    5.84249059e-01 1.02377362e-01 8.85885970e-01

which yields a boundary box in the new frame:
    2.58354960e-01 1.31042927e+00 5.39674600e-01
    1.35092063e+00 1.40299843e+00 6.01082609e-01

with a total bound volume of 6.21067619e-03
---------------------------------------------



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