[yt-users] Tipsy Stellar Ages

[Desika Narayanan]

Hey Nathan,

This is great - thanks!

-d


On Mon, Mar 30, 2015 at 2:24 PM, Nathan Goldbaum <nathan12343 at gmail.com>
wrote:

>
> On Mon, Mar 30, 2015 at 11:10 AM, Desika Narayanan <dnarayan at haverford.edu
> > wrote:
>
>> Hi All,
>>
>> I'm trying to understand some of the stellar ages that the Tipsy example
>> data (the isolated galaxy) at:
>>
>> http://yt-project.org/data/
>>
>> When I examine the formation time with the super-simple script:
>>
>> http://paste.yt-project.org/show/5501/
>>
>> I get:
>>
>> max star age:  100.000499852 Gyr
>>
>> I thought normally the formation time was the current simulation time
>> minus the stellar age for Tipsy outputs - am I interpreting this wrongly?
>>
>>
>>
> Hi Desika,
>
> I encountered this before.  Take a look at the following section of the
> docs, which makes use of this dataset:
>
>
> http://yt-project.org/docs/dev/analyzing/filtering.html#filtering-particle-fields
>
> I don't have a copy of gasoline to confirm this, but the conclusion I came
> to is that the stars in the initial conditions for this simulation were
> given a creation time arbitrarily far in the future, generating spurious
> stellar ages.
>
> If you instead define particle filters for formed stars like so:
>
> def young_stars(pfilter, data):
>     age = data.ds.current_time - data[pfilter.filtered_type,
> "creation_time"]
>     filter = np.logical_and(age.in_units('Myr') <= 5, age >= 0)
>     return filter
>
> def old_stars(pfilter, data):
>     age = data.ds.current_time - data[pfilter.filtered_type,
> "creation_time"]
>     filter = np.logical_or(age.in_units('Myr') >= 5, age < 0)
>     return filter
>
> where I've arbitrarily chosen 5 Myr as the cutoff for old stars and young
> stars, you'll find that your results make more sense.
>
> HTH,
>
> Nathan
>
>> Thanks,
>> desika
>>
>>
>>
>>
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>>
>
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