TY - JOUR

T1 - 2MTF VI. Measuring the velocity power spectrum

AU - Howlett, Cullan

AU - Staveley-Smith, Lister

AU - Elahi, Pascal J.

AU - Hong, Tao

AU - Jarrett, Tom H.

AU - Jones, David Heath

AU - Koribalski, Bärbel S.

AU - Macri, Lucas M.

AU - Masters, Karen L.

AU - Springob, Christopher M.

N1 - 18 pages, 14 figures, 3 tables. Accepted for publication in MNRAS

PY - 2017/11

Y1 - 2017/11

N2 - We present measurements of the velocity power spectrum and constraints on the growth rate of structure ƒσ8, at redshift zero, using the peculiar motions of 2,062 galaxies in the completed 2MASS Tully-Fisher survey (2MTF). To accomplish this we introduce a model for fitting the velocity power spectrum including the effects of non-linear Redshift Space Distortions (RSD), allowing us to recover unbiased fits down to scales k = 0.2 h Mpc-1 without the need to smooth or grid the data. Our fitting methods are validated using a set of simulated 2MTF surveys. Using these simulations we also identify that the Gaussian distributed estimator for peculiar velocities of Watkins & Feldman (2015) is suitable for measuring the velocity power spectrum, but sub-optimal for the 2MTF data compared to using magnitude fluctuations δm, and that, whilst our fits are robust to a change in fiducial cosmology, future peculiar velocity surveys with more constraining power may have to marginalise over this. We obtain scale-dependent constraints on the growth rate of structure in two bins, finding ƒσ8 = [0.55 +0.16 -0.13, 0.40 +0.16 -0.17] in the ranges k = [0.007-0.055, 0.55-0.150] h Mpc-1. We also find consistent results using four bins. Assuming scale-independence we find a value ƒσ8 = 0.51 +0.09 -0.08, a ∼16% measurement of the growth rate. Performing a consistency check of General Relativity (GR) and combining our results with CMB data only we find γ = 0.45 +0.10 -0.11, a remarkable constraint considering the small number of galaxies. All of our results are completely independent of the effects of galaxy bias, and fully consistent with the predictions of GR (scale-independent ƒσ8 and γ ≈ 0.55).

AB - We present measurements of the velocity power spectrum and constraints on the growth rate of structure ƒσ8, at redshift zero, using the peculiar motions of 2,062 galaxies in the completed 2MASS Tully-Fisher survey (2MTF). To accomplish this we introduce a model for fitting the velocity power spectrum including the effects of non-linear Redshift Space Distortions (RSD), allowing us to recover unbiased fits down to scales k = 0.2 h Mpc-1 without the need to smooth or grid the data. Our fitting methods are validated using a set of simulated 2MTF surveys. Using these simulations we also identify that the Gaussian distributed estimator for peculiar velocities of Watkins & Feldman (2015) is suitable for measuring the velocity power spectrum, but sub-optimal for the 2MTF data compared to using magnitude fluctuations δm, and that, whilst our fits are robust to a change in fiducial cosmology, future peculiar velocity surveys with more constraining power may have to marginalise over this. We obtain scale-dependent constraints on the growth rate of structure in two bins, finding ƒσ8 = [0.55 +0.16 -0.13, 0.40 +0.16 -0.17] in the ranges k = [0.007-0.055, 0.55-0.150] h Mpc-1. We also find consistent results using four bins. Assuming scale-independence we find a value ƒσ8 = 0.51 +0.09 -0.08, a ∼16% measurement of the growth rate. Performing a consistency check of General Relativity (GR) and combining our results with CMB data only we find γ = 0.45 +0.10 -0.11, a remarkable constraint considering the small number of galaxies. All of our results are completely independent of the effects of galaxy bias, and fully consistent with the predictions of GR (scale-independent ƒσ8 and γ ≈ 0.55).

KW - astro-ph.CO

KW - cosmology: observations

KW - large scale structure of the universe

KW - cosmological parameters

U2 - 10.1093/mnras/stx1521

DO - 10.1093/mnras/stx1521

M3 - Article

SN - 0035-8711

VL - 471

SP - 3135

EP - 3151

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

ER -