==================
Notes on k-correct
==================

FW High
fwhigh@fas.harvard.edu
5/12/2006

INSTALLATION
------------

Google "blanton k-correct" and the first hit will likely be Roger
Blanton's NYU k-correct page. This page has most of the information
you need about obtaining and installing k-correct. This section I am
writing is merely a supplement to that information.

Follow his instructions on obtaining and unpacking the code. This
means get and install idlutils as instructed. You will eventually come
to the point where you need to make using something called
"kevilmake". It is my impression that you can just as well use make
itself, or maybe evilmake, which lives in $IDLUTILS_DIR/bin, which you
should have already installed.

*NOTE: Actually, `make` does not work, while `evilmake` does. So
follow the instructions on the website.


ACCESSING THE TEMPLATES
-----------------------

The photo-z principle relies on fitting galaxy colors to a well
characterized galaxy spectrum template that happens to have a
significant break in flux at 400 nm (at z=0). This template is called
the Luminous Red Galaxy, or LRG. Roger takes a handful of different
templates (5, I believe) and fits color measurements to them, with the
redshift of the spectrum left as a free parameter. If the best fit
spectrum turns out to be the LRG template, then the corresponding best
fit redshift gives us our redshift estimate---our photo-z. This is my
impression, anyhow.

These templates can be accessed directly from k-correct. After
installing k-correct and setting the appropriate IDL csh macros as
instructed, within IDL type

IDL> k_load_vmatrix, vmatrix, lambda 

You now have the 5 templates loaded into vmatrix. You can plot
these. For example, plot the LRG template

IDL> plot,lambda,vmatrix[*,3], xra=[2000., 12000.]

A description of these templates appears in

http://cosmo.nyu.edu/blanton/kcorrect/kcorrect.ps.gz