Wiki¶

This can be divided into 3 steps

Step 1 run modelfitting photometry¶

you can find the scripts at /big/users/shantanu/VLTmfp/catalogs/runmfp_b.sh (for b band and so on)

note that since initial catalogs will be uncalibrated , use -mag_zeropoint for b,I and z bands.
The zeropoints for HST bands is :
F606W 26.493mag, F814W 25.947mag.
the sextractor param file used in the scripts is
/big/des_home/stable/etc/sex.param_sersic
you can edit to remove params you don't need.

Produce a matched catalog across all 4 bands¶

This is the most tedious step. Unfortunately you cannot run sextractor in dual image mode
since coadds are of different size.
The way I did it was to run a modified version of a code
used in DESDM called coadd_grabmatches. I first ran it to match R vs I band and then used
that match catalog to match against z band and so on.
A code to do this is at /home/moon/shantanu/desdm/devel/ImageProc/trunk/src/coadd_grabmatches_singleband.c
There is one line in the code (below # 266) which needs to be changed depending upon number of coluns
in input catalog.
Once this is done you need to make a file with the matched magnitudes in all four bands
(its possible to automate this script with some effort so that it does not need to be changed)

Doing the stellar locus¶

One you have the catalogs all you need to do is to do a fit by eye or quantitative to SED fits provided by Joerg.
Here is my 2nd order polynomial curve fit done to these relations

1) b-R vs R-I
b -R = -0.2904*x^2+1.319x +0.2941
(where x=R-I)

2) R-I vs I -z
R-I = -1.016*x^2+ 3.532*x +0.1294
where x=I-z

3) b-R vs I-z
R-I = -2.20378*x^2+ 3.96368*x +0.386878

I did the plotting in ROOT, but probably it can be done in any software.