clustering of galaxies

[mr-superonion]

We need to create a galaxy distribution object to enable using realistic galaxy clustering from simulations or physical models..

[esheldon]

We current set layout as a string, it could also be an object

[mr-superonion]

I add Layout object in shfits.py, see here

[mr-superonion]

@beckermr , do you have any plan to get the clustering? I am thinking of using some Gaussian field/ log-normal random filed to get the shear and kappa field. probably it is better to add clustering that is consistent with the shear / kappa field (caused by the same cosmological density field)..

[beckermr]

I think this kind of thing is likely beyond the scope of this repo. We assembled the code here to build very simple simulations that are easy to test and verify.

[mr-superonion]

Oh, I am planning to use it to estimate some second order effect. e.g, kappa dependence of shear response and how this changes the measurement of cosmic shear power spectrum measurement. If that is single redshift plan and no irregular spacial mask, this should be very simple and well-defined, I think. (basically just changing the shear signal and/or the galaxy distributions)
Hmm, It should be very simple, I imagine, one simulation with clustering or kappa distortion v.s. one without.

I would like to say that I am very confident to figure out the reason of any systematic with this simulation if we increase the complicity step by step from the point we know that it is unbiased..

[beckermr]

You all should feel free to go ahead. Sorry I was a pain on this one. I still want to register my worries about scope expansion, but I don't want to block anyone from doing good work.

[zhouconghao]

Hi All,

A few folks chatted about getting realistic cluster image simulations for testing shear calibration near clusters in the sprint day last week. It would be really great if we can do this here. I saw this issue and it seems to be related to what we want to do. Maybe we can start the discussion in this issue about the first steps here?

I think creating a galaxy class called ClusterGalaxyCatalog where it reads predefined positions and fluxes from clusters from real clusters or simulations might be a first step. I'll go ahead and try this. Let me know if there are better ways or I should do something else.