2MTF IV. A bulk flow measurement of the local Universe

Using the 2MASS near-infrared photometry and high-signal-to-noise HI 21-cm data from the Arecibo, Green Bank, Nancay, and Parkes telescopes, we calculate the redshift-independent distances and peculiar velocities of 2018 bright inclined spiral galaxies over the whole sky. This project is part of the 2MASS Tully-Fisher survey (2MTF), aiming to map the galaxy peculiar velocity field within 100 h⁻¹ Mpc, with an all-sky coverage apart from Galactic latitudes |b|<5◦. A χ2 minimization method was adopted to analyse the Tully–Fisher peculiar velocity field in J, H, and K bands, using a Gaussian filter. We combine information from the three wavebands, to provide bulk flow measurements of 310.9 ± 33.9 , 280.8 ± 25.0, and 292.3 ± 27.8 km s⁻¹ at depths of 20, 30, and 40 h⁻¹ Mpc, respectively. Each of these bulk flow vectors points in a direction similar to those found by previous measurements. At each of the three depths, the bulk flow magnitude is consistent with predictions made by the cold dark matter (CDM) model at the 1σ level. The maximum likelihood and minimum variance method were also used to analyse the 2MTF samples, giving similar results.