Science and Pretty Pictures

SpaceTiger

New member
I gave a talk recently and the slides had some nice pictures that you guys might appreciate. Here's the power point file (very large):

http://www.astro.princeton.edu/~nbond/ox-princeton.pptTalk</a>

For those who don't want to bother with that, I'll give a quick summary and some examples.

The basic idea is that I'm looking for filaments in the large-scale galaxy distribution. Here's an example of a chunk of the universe from a cosmological simulation:

http://www.astro.princeton.edu/~nbond/0_points2d_2.JPGPoints</a>

The points represent galaxies. The basic method I use to find filaments is to explore the first and second derivatives of the density field. Here are some plots of that:

http://www.astro.princeton.edu/~nbond/0_vectors_2.JPGFirst</a> (gradient vectors)
http://www.astro.princeton.edu/~nbond/0_secderiv_xx_2.JPGSecond</a> (xx component)
http://www.astro.princeton.edu/~nbond/bars_2.JPGSecond</a> (Direction of filament)

What you're looking at in the first is the direction of maximum increase in density at each grid point. In the second, I plotted a grayscale of the curvature in the x direction at each grid point. Finally, in the last, I found the minor axis of the second derivative ellipse, which is supposed to indicate the direction of the filament.

Anyway, I know my description is a bit dense, but it's worth just looking at the pictures, I think. The universe is pretty cool looking when you get down to it.

<P ID="signature">----
"And dreams may come
That are everlasting
Though all just plastic too..." </P>
 
Top Bottom