[yt-users] Sudden fluctuations in the projected density

[Maan Hani]

Hi all,

While performing projections of the density ?field in a cosmological zoom-in simulation, I noticed sudden fluctuations between the projected density of consecutive snapshots. I thought the fluctuations were due to interlopers entering the field of view (I was looking at the zoom-in region of the box). However, regardless what region of the cosmological box I plot (below I project the whole cosmological box), the fluctuation remains. Note that the fluctuation is not seen in the particle data.

Please let me know if this issue is reproducible by others (I'm using yt 3.4-dev) and how I could go about solving it.

I've attached a simple sample script and the projection output. The projections are made using Arepo data, but I am treating the data as a Gadget Dataset in yt. The data is available at: http://use.yt/upload/44604f23 and http://use.yt/upload/a5e7f213

Output:
- snapshot1: http://i.imgur.com/a3w6vVn.png
- snapshot2: http://i.imgur.com/Bq5xlOB.png?

Sample script:
```
# importing libraries
import yt
from yt.frontends.gadget.data_structures import GadgetHDF5Dataset

# reading snapshot data
ds1     = GadgetHDF5Dataset('../data/1605-2/snapshot_052.hdf5')
ds2     = GadgetHDF5Dataset('../data/1605-2/snapshot_053.hdf5')

# density un-weighted projections
proj1 = yt.ProjectionPlot(ds1, 'z', ('gas','density'))
proj2 = yt.ProjectionPlot(ds2, 'z', ('gas','density'))

proj1.set_zlim('density', 1.E-4, 1.E-2)
proj2.set_zlim('density', 1.E-4, 1.E-2)

proj1.save()
proj2.save()
```

Thanks,
Maan?

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