[yt-users] ramses dataset structure

Desika Narayanan dnarayan at haverford.edu
Tue Jun 2 07:38:42 PDT 2015


Hey Ben,

This is really helpful - thanks a lot!

-d

On Tue, Jun 2, 2015 at 9:58 AM, Ben Thompson <bthompson2090 at gmail.com>
wrote:

> Hi Desika.
>
>
>> 1. How should I interpret the particle data outputs from a Ramses data
>> set?
>>
>
> What you were doing is fine, i.e
>
> ad[ ('io', 'particle_mass')]).in_units('Msun')
>>
>
> i.e that should print a YTArray of the mass of each individual particle.
> Unless your RAMSES simulation is outputting the particle mass differently
> into the binary data (which the example snapshots do not since they were
> made with an unmodified version of RAMSES), then what you are outputting
> should be fine. Likewise your script is doing exactly that. I.e summing the
> mass of *all* the particles in the dataset.
>
> 2. Relatedly - is there an obvious way to extract just the information
>> about stars from a ramses data set?   (Assuming the particles are made up
>> of only dark matter and stars...though maybe I have that wrong?)
>>
>
> You will have to create a particle filter. Since RAMSES uses the particle
> fields for the dark matter particle and star particle fields, you will need
> to employ a particle filter. Something along the lines of:
>
> def star_filter(pfilter,data):	filter = np.logical_and(data.particles.source["particle_age"] != 0, data.particles.source["particle_age"] != None)	return filter
>
> Then followed by:
>
> add_particle_filter("stars", function=star_filter, filtered_type="all", requires=["particle_age"])
> ad.ds.add_particle_filter("stars")
>
> Which will allow you to filter your dataset for star particles.
> However, this assumes that there are start particles. If there is no star
> formation in the simulation, then the "particle_age" field does not get
> created.
>
> You can read more about filters here
> http://yt-project.org/doc/analyzing/filtering.html
>
>>
>>
>> 3.  If I run the same script with the Output 00101 (Cosmology output)
>> from the yt Ramses data sets, I find that a derived field list doesn't list
>> anything that's obviously for the gas.  Unless this is the 'deposit' fields
>> (which my gadget-centric brain thinks is related to an octree deposition
>> somehow).
>>
>
> That is because there is no gas data in that simulation. That run is an
> NBody-only run. If the gas cells are not there, then the YT dataset object
> has no gas data to read in, and thus no gas fields are created.
>
> Hope this helps.
>
> Ben.
>
> On Tue, Jun 2, 2015 at 10:41 AM, Desika Narayanan <dnarayan at haverford.edu>
> wrote:
>
>> Hi All,
>>
>> I have a couple of very super basic questions about how Ramses data sets
>> are organized which I think are all related (and rooted in my total
>> ignorance of Ramses outputs).
>>
>> 1. How should I interpret the particle data outputs from a Ramses data
>> set?
>>
>> http://paste.yt-project.org/show/5579
>>
>> on a yt example data set, I get a total particle mass of  total particle
>> mass =  1.13468176647e+16 Msun
>>
>> What particles does this encompass?  It seems large even for dark matter
>> and stars.
>>
>> 2. Relatedly - is there an obvious way to extract just the information
>> about stars from a ramses data set?   (Assuming the particles are made up
>> of only dark matter and stars...though maybe I have that wrong?)
>>
>> 3.  If I run the same script with the Output 00101 (Cosmology output)
>> from the yt Ramses data sets, I find that a derived field list doesn't list
>> anything that's obviously for the gas.  Unless this is the 'deposit' fields
>> (which my gadget-centric brain thinks is related to an octree deposition
>> somehow).
>>
>> Thanks!
>> -desika
>>
>>
>>
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>>
>>
>
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