<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><div dir="ltr">Hey Nathan,<div><br></div><div>This is great - thanks!</div><div><br></div><div>-d</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Mar 30, 2015 at 2:24 PM, Nathan Goldbaum <span dir="ltr"><<a href="mailto:nathan12343@gmail.com" target="_blank">nathan12343@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Mon, Mar 30, 2015 at 11:10 AM, Desika Narayanan <span dir="ltr"><<a href="mailto:dnarayan@haverford.edu" target="_blank">dnarayan@haverford.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr">Hi All,<br><div><br></div><div>I'm trying to understand some of the stellar ages that the Tipsy example data (the isolated galaxy) at:</div><div><br></div><div><a href="http://yt-project.org/data/" target="_blank">http://yt-project.org/data/</a></div><div><br></div><div>When I examine the formation time with the super-simple script:</div><div>
<p><a href="http://paste.yt-project.org/show/5501/" target="_blank">http://paste.yt-project.org/show/5501/</a></p><p>I get: </p><p>
</p><p>max star age: 100.000499852 Gyr</p><p>I thought normally the formation time was the current simulation time minus the stellar age for Tipsy outputs - am I interpreting this wrongly?</p><p><br></p></div></div></blockquote><div><br></div></div></div><div>Hi Desika,</div><div><br></div><div>I encountered this before. Take a look at the following section of the docs, which makes use of this dataset:</div><div><br></div><div><a href="http://yt-project.org/docs/dev/analyzing/filtering.html#filtering-particle-fields" target="_blank">http://yt-project.org/docs/dev/analyzing/filtering.html#filtering-particle-fields</a><br></div><div><br></div><div>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.</div><div><br></div><div>If you instead define particle filters for formed stars like so:</div><div><br></div><div><div>def young_stars(pfilter, data):</div><div> age = data.ds.current_time - data[pfilter.filtered_type, "creation_time"]</div><div> filter = np.logical_and(age.in_units('Myr') <= 5, age >= 0)</div><div> return filter</div><div><br></div><div>def old_stars(pfilter, data):</div><div> age = data.ds.current_time - data[pfilter.filtered_type, "creation_time"]</div><div> filter = np.logical_or(age.in_units('Myr') >= 5, age < 0)</div><div> return filter</div></div><div><br></div><div>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.</div><div> </div><div>HTH,</div><div><br></div><div>Nathan</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><p></p><p>Thanks,<br>desika</p><p><br></p><p><br></p></div></div>
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