Closed cwwalter closed 8 years ago
Have a look at the QA notebook done on the full catalog (github nicely opens it)
Comments:
So, someone should comment on whether correlation function is worrying or is it just a millenium sim limitation. Or I made a silly mistake.
Mentioning @egawiser and @danielsf since they are not watching the repo and might not see this issue.
Also letting @dkirkby know about this thread..
It looks like xi*r^2
is closer to -1 at 50Mpc in the CMASS redshift range (0.5-1). What does the xi*r^2
plot look like if you extend it beyond the BAO scale?
Pure noise. But note that at 200Mpc, you are approaching millenium box size and so the integral constraint is going to start to affect you etc. Maybe you could also throw an eye to see if there is an obvious bug in how i calculate xi.
@fjaviersanchez is going to take a look
So, I used TreeCorr with 25% of the sample, but I generated the random catalog differently, and read the data differently. It would be a very strange coincidence if we both made the same mistake. I am getting essentially the same results as @slosar. I also made this plot to check the magnitude and redshift distributions with 1% of the objects. Green histograms/points correspond to the gold sample and blue to the total sample:
My version of the notebook can be found here: https://github.com/fjaviersanchez/test_catsim/blob/master/Test_CatSim.ipynb
This is what I think it's going on:
I am also computing the correlation function with some other code but, I don't expect much of a difference since TreeCorr is well tested.
@fjaviersanchez , this is great! I think this establishes that the if it is a problem, it is in the catalog, but it is not even clear it is a problem. True, at z=0.25 you don't have very much volume, but at z=1.0 you have a box some 200Mpc wide and very long, so I would expect it to work a bit better. I suggest we move on with this but assume we won't be able to do much more than that a couple of Mpc, even assuming perfect photozs...
I am going to wait for two days until @slosar comes back from vacation so my email isn't 'BLACK HOLED' to finalize and ask to close him to close this, but my discussion with @fjaviersanchez leads me to believe the differences we see are due to variance and the effects of tiling at the size of the box are in the noise of the correlation function.
@fjaviersanchez can you confirm this is your conclusion?
@cwwalter Yes, that looks correct. We are not sensitive to the repetition of the box using the correlation function (at least the monopole) given the size of the patch
@slosar I see evidence you are back from your summer sojourns. Please look at this thread and my proposal to close this issue.
Yes, I'm happy enough to close this issue, but let's keep in mind that correlation func is not really measurable beyond 20-30 Mpc.
Anže will do sanity check on a CatSim based galaxy catalog of 80 sq degrees to see if the angular clustering is reasonable . The catalog is created by @danielsf as outlined in #3.