t00fri wrote:I have also right away suggested that you should use the higher order comoving definition of distance, which you now correctly did...
You would have right away realized that the straight radial patterns in my Celestia database are NOT artefacts, but the onset of the famous large scale structure seen so clearly in the Sloan DSS.
Fridger,
I did used the comoving distance for the clusters ! The difference (small z) is really tiny in their case. The difference can be noticeable for z around 1, and it's more important in the case of the CMOD model based on the LOAN database.
In the case of your database, there are several galaxies which are standing on the surface of spheres, like these two examples :
This is certainly not "physical", and a proof that there are strong uncertainties and/or systematic errors on radial distances (I already indicated these cases to you, a long time ago while you were in the process of building the database. On my suggestion, you accepted to leave them the way they are, since they are good examples of the kind of distance uncertainties we can find in any astronomical databases). Also, the radial lines I was talking about can be made to disappear on the SLOAN models, since there's a "confidence" constraint. For the model I made, I used the same constraints as Selden : minimal confidence 0.2, which is pretty low. It isn't suprising that there are radial artifacts in this case. Using an higher level confidence (0.7, say) filters all the uncertain galaxies and removes the radial artifacts. I'm building another CMOD model right now without these radial lines (there are less galaxies, though, so the model is less "strong" in Celestia).
