The dipole anisotropy of the 2 Micron All-Sky Redshift Survey

June 2006 • 2006MNRAS.368.1515E

Authors • Erdoǧdu, P. • Huchra, J. P. • Lahav, O. • Colless, M. • Cutri, R. M. • Falco, E. • George, T. • Jarrett, T. • Jones, D. H. • Kochanek, C. S. • Macri, L. • Mader, J. • Martimbeau, N. • Pahre, M. • Parker, Q. • Rassat, A. • Saunders, W.

Abstract • We estimate the acceleration on the Local Group (LG) from the 2 Micron All-Sky Redshift Survey (2MRS). The sample used includes about 23200 galaxies with extinction-corrected magnitudes brighter than K_s= 11.25 and it allows us to calculate the flux-weighted dipole. The near-infrared flux-weighted dipoles are very robust because they closely approximate a mass-weighted dipole, bypassing the effects of redshift distortions and require no preferred reference frame. This is combined with the redshift information to determine the change in dipole with distance. The misalignment angle between the LG and the cosmic microwave background (CMB) dipole drops to 12°+/- 7° at around 50h^-1Mpc, but then increases at larger distances, reaching 21°+/- 8° at around 130h^-1Mpc. Exclusion of the galaxies Maffei 1, Maffei 2, Dwingeloo 1, IC342 and M87 brings the resultant flux dipole to 14°+/- 7° away from the CMB velocity dipole. In both cases, the dipole seemingly converges by 60h^-1Mpc. Assuming convergence, the comparison of the 2MRS flux dipole and the CMB dipole provides a value for the combination of the mass density and luminosity bias parameters Ω^0.6_m/b_L= 0.40 +/- 0.09.

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Roc Cutri

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