Tagged: Astro

Searching for Nearest-Neighbors between Two Coordinate Catalogs

Written by Taro Sato, on . Tagged: stats astro

Say I have two catalogs of points, each in two-dimensional space. For each object in a catalog, I want to find the nearest object(s) in the other catalog. I can do this by computing the distances between every single unique pair of objects and finding the ones within a search radius and possibly doing an additional sort. ... Continue reading.

Half-Light Radii for Various Profiles

Written by Taro Sato, on . Tagged: astro math

For a radial profile of \(I( r)\), the enclosed flux within the radius \(r\) is given by \begin{equation*} F( r) = \int_{0}^{2 \pi} d\phi \int_{0}^{r} dr r I(r, \phi) \ . \end{equation*} I’m only concerned about azimuthal symmetric cases, so \(F( r) = 2\pi \int_{0}^{r} dr r I( r)\) . ... Continue reading.

Installing SExtractor on Mac OS X Snow Leopard

Written by Taro Sato on . Tagged: astro sysadmin OS X

(November 25, 2010) I screwed up SExtractor installation for no reason and in an attempt to fix it, I’ve found a few things. After wasting a few hours again, I think this installation note can work for most people who can actually build software from source… I think the usefulness of this note will be limited though, as a new release of SExtractor appears imminent. ... Continue reading.