Bulk flow and shear in the local Universe: 2MTF and COSMICFLOWS3
Abstract
The loworder kinematic moments of galaxies, namely bulk flow and shear, enables us to test whether theoretical models can accurately describe the evolution of the mass density field in the nearby Universe. We use the socalled ηMLE maximum likelihood estimator in logdistance space to measure these moments from a combined sample of the 2MASS TullyFisher (2MTF) survey and the COSMICFLOWS3 (CF3) compilation. Galaxies common between 2MTF and CF3 demonstrate a small zeropoint difference of 0.016 ± 0.002 dex. We test the ηMLE on 16 mock 2MTF survey catalogues in order to explore how well the ηMLE recovers the true moments, and the effect of sample anisotropy. On the scale size of 37 h^{1} Mpc, we find that the bulk flow of the local Universe is 259 ± 15 km s^{1} in the direction is (l, b) = (300 ± 4°, 23 ± 3°) (Galactic coordinates). The average shear amplitude is 1.7 ± 0.4 h km s^{1} Mpc^{1}. We use a variable window function to explore the bulk and shear moments as a function of depth. In all cases, the measurements are consistent with the predictions of the Λ cold dark matter (ΛCDM) model.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2019
 DOI:
 10.1093/mnras/sty2826
 arXiv:
 arXiv:1811.00822
 Bibcode:
 2019MNRAS.482.1920Q
 Keywords:

 surveys;
 galaxies: statistics;
 largescale structure of Universe;
 cosmology: observations;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 11 pages, 10+2 figures, published in MNRAS, Oct/2018