The linear velocity field of 2MASS Redshift Survey, K_s= 11.75 galaxies: Constraints on β and bulk flow from the luminosity function

Using the nearly full-sky K_s= 11.75 2MASS Redshift Survey (2MRS; Huchra et al.) of ∼45000 galaxies, we reconstruct the underlying peculiar velocity field and constrain the cosmological bulk flow within ∼100h^-1Mpc. These results are obtained by maximizing the probability to estimate the absolute magnitude of a galaxy given its observed apparent magnitude and redshift. At a depth of ≈60h^-1Mpc, we find a bulk flow in agreement with the theoretical predictions of the Λ cold dark matter model. The reconstructed peculiar velocity field that maximizes the likelihood is characterized by the parameter β= 0.32 ± 0.08. Both results are in agreement with those obtained previously using the ∼23000 galaxies of the shallower K_s= 11.25 2MRS survey. In our analysis, we find that the luminosity function of 2MRS galaxies is poorly fitted by the Schechter form and that luminosity evolves such that objects become fainter with increasing redshift according to L(z) =L(z= 0)(1 +z)^{+2.7 ± 0.15}.