I've been trying to figure out why my 2d Correlation Functions look weird. I've put out request to several Berkeley folks to compare my correlation function results on a data set with theirs, but while I wait for them to respond, I'm going to compare to some literature.

For the 2-d angular correlation function on SDSS LRG galaxies, I have the following plots from Connolly et al (2001):

And from Ross et al (2007):

I changed the angular bins of my correlation function to match these sets to try to form a comparison. Here is my 2D correlation function on BOSS data:

As you can see the slope of the function is much shallower for my correlation function, than it is the literature.

The 3D correlation functions are a better match:

From Ross et al (2007):

And here is mine:

At least the slopes seem to be comparable.

I am currently running the 3D correlation function on a larger los range to try to compare to Kazin et al. :

This will take a bit because I am correlating out to such large scales (180 Mpc/h).

Another thing I noticed that I wanted to talk to Alexia about is the actual computation of the correlation function in the code. Right now it is the following:

xi = (dd - dr - rd + rr)/rr

where

dd = # of data-data pairs in bin

dr = (# if data-random pairs in bin) / (Random Oversampling)

rd = (# if data-random pairs in bin) / (Random Oversampling)

rr = (# if random-random pairs in bin) / (Random Oversampling)

I am wondering if the rr should be divided by (random oversampling)^2 because there are that many more point in the RR set. I haven't changed this code from when I first got it from Alexia, so I assume it is correct. But I was looking the Landy, Szalay Paper and it seemed like they were using factors of n(n-1)/2 which is approximately n^2, and we are using factors of n.

Thoughts?

3/21 5:15 Update: Here is my plot of the 3d Correlation function on the large los range, it looks very similar to the Kazin plot above, you can even see the BAO signal @ ~100 Mpc/h:

## Monday, March 21, 2011

### Comparing Correlation Functions

Labels:
2D,
3D,
Alexia Schulz,
BOSS,
correlation function,
Eyal Kazin,
Nic Ross,
SDSS

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