Hi Nathan, Thank you for your kind reply! Yes, I have noticed this part, but there is always some mistakes. In my Gadget data, ('PartType0', 'ElectronAbundance') is not a initial field, so I derived it by manumotive. Firstly, I set it equal to 1.15, and checked it is normal: -------------------------------------------------------------------------------------------------------------------------------------------

@derived_field(name=("PartType0","ElectronAbundance"),particle_type=True, force_override=True)

def _ElectronAbundance(field,data): return 1.15

print(ad['PartType0','ElectronAbundance']) 1.15 dimensionless

Then the corresponding fields: -------------------------------------------------------------------------------------------------------------------------------------------

print(ad['PartType0','InternalEnergy'].in_units('km**2/s**2')[8000]) 193516.9375 km**2/s**2 print(ad['gas','kT'][8000]) 1.609844329629573 keV

I don't think the value of kT is right, so I made a test: -------------------------------------------------------------------------------------------------------------------------------------------

@derived_field(name=("PartType0","ElectronAbundance"),particle_type=True, force_override=True)

def _ElectronAbundance(field,data): return 0

print(ad['PartType0','ElectronAbundance']) 0.0 dimensionless

print(ad['PartType0','InternalEnergy'].in_units('km**2/s**2')[8000]) 193516.9375 km**2/s**2 print(ad['gas','kT'][8000]) 1.609844329629573 keV

To my amazement, I got a same value of kT, though I changed the ("PartType0","ElectronAbundance"). I'm confused about it. Is there any points I didn't realize? Thank you again! Regard, Dan On 01/02/2017 10:50 PM, Nathan Goldbaum wrote:

Hi Dan,

This particular field is defined specifically for Gadget data in the Gadget frontend:

https://bitbucket.org/yt_analysis/yt/src/09f0ef297d7068078a021fc8290d9e3519baf82d/yt/frontends/gadget/fields.py?at=yt&fileviewer=file-view-default#fields.py-72

Nathan

On Mon, Jan 2, 2017 at 6:33 AM hudan_bazhaoyu mailto:hudan_bazhaoyu@sjtu.edu.cn> wrote:

Dear yt:

I have one simple question, but it bothers me these days.

I used the yt to analysis the "hdf5" files, which generated by

Gadget-2. These files have basic fields, like: ("PartType0", "*"),

("PartType1", "*") and ("all", "*"). Then I want to plot the density

map and temperature map, it seems need some derived fields, like:

("gas", "density") and ("gas", "temperature").

I'm curious about how the ("gas","temperature") was derived, so I

browsed a lots of documents on the Web, but found nothing. Please

see

http://yt-project.org/doc/reference/field_list.html?highlight=field%20list

About the field of ('gas','temperature'), there is "No source

available" in "Field Source"!

In my data, the field ("PartType0","InternalEnergy") is provided by

me, and I think the temperature should calculated by Internal Energy

"E" with the function: k*T = (Gamma -1)*µ*mp*E, where k = 1.38E-16

erg/K is Boltzmann constant, Gamma = 5/3 for adiabat particles, μ =

0.6 is the corresponding mean molecular weight, and mp = 1.67E-24 g

is proton mass. But this result is about half of the value of

("gas","temperature").

So what you may know is why, which one is right? I need your help!

Thank you a lot, and happy new year!

Regard,

Dan

--

Dan Hu

=======================================

Department of Physics, Shanghai Jiao Tong

University

800 Dongchuan Road, Minhang, Shanghai 200240, PRC

E-mail : hudan_bazhaoyu@163.com mailto:hudan_bazhaoyu@163.com

hudan_bazhaoyu@sjtu.edu.cn mailto:hudan_bazhaoyu@sjtu.edu.cn

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