Is the 2MASS dipole convergent?

TL;DR

This study investigates whether the 2MASS galaxy clustering dipole converges within 300 Mpc/h, finding that its growth aligns with LambdaCDM predictions when the survey's observational window is properly considered, allowing estimation of cosmological parameters.

Contribution

It demonstrates that the 2MASS dipole growth is consistent with theoretical models when the correct observational window is used, providing a new method to estimate cosmological parameters from galaxy surveys.

Findings

The 2MASS dipole does not converge before 300 Mpc/h.

Observed dipole growth matches LambdaCDM predictions with proper window correction.

Estimated beta parameter as 0.38+-0.05, implying Omega_m around 0.2+-0.1.

Abstract

We study the growth of the clustering dipole of galaxies from the Two Micron All Sky Survey (2MASS). We find that the dipole does not converge before the completeness limit of the 2MASS Extended Source Catalog, i.e. up to about 300 Mpc/h. We compare the observed growth of the dipole with the theoretically expected, conditional growth for the LambdaCDM power spectrum and cosmological parameters constrained by WMAP. The observed growth turns out to be within 1-sigma confidence level of the theoretical one, once the proper observational window of the 2MASS flux dipole is included. For a contrast, if the adopted window is a top hat, then the predicted dipole grows significantly faster and converges to its final value at a distance of about 200 Mpc/h. We study the difference between the top-hat window and the window for the flux-limited 2MASS survey and we conclude that the growth of the 2MASS dipole at effective distances greater than 200 Mpc/h is only apparent. Eventually, since for the window function of 2MASS the predicted growth is consistent with the observed one, we can compare the two to evaluate beta = (Omega_m)^0.55 / b. The result is beta = 0.38+-0.05, which gives a rough estimate of Omega_m = 0.2+-0.1.