Gaussianization of peculiar velocities and bulk flow measurement. (arXiv:2105.04800v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Qin_F/0/1/0/all/0/1">Fei Qin</a>
The line-of-sight peculiar velocities are good indicators of the
gravitational fluctuation of the density field. Techniques have been developed
to extract cosmological information from the peculiar velocities in order to
test the cosmological models. These techniques include measuring cosmic flow,
measuring two-point correlation and power spectrum of the peculiar velocity
fields, reconstructing the density field using peculiar velocities. However,
some measurements from these techniques are biased due to the non-Gaussianity
of the estimated peculiar velocities. Therefore, we use the 2MTF survey to
explore a power transform that can Gaussianize the estimated peculiar
velocities. We find a tight linear relation between the transformation
parameters and the measurement errors of log-distance ratio. To show an example
for the implement of the Gaussianized peculiar velocities in cosmology, we
develop a bulk flow estimator and estimate bulk flow from the Gaussianized
peculiar velocities. We use 2MTF mocks to test the algorithm, we find the
algorithm yields unbiased measurements. We also find this technique gives
smaller measurement errors compared to other techniques. Under the Galactic
coordinates, at the depth of $30$ $h^{-1}$ Mpc, we measure a bulk flow of
$332pm27$ km s$^{-1}$ in the direction $(l,b)=(293pm 5^{circ}, 13pm
4^{circ})$. The measurement is consistent with the $Lambda$CDM prediction.
The line-of-sight peculiar velocities are good indicators of the
gravitational fluctuation of the density field. Techniques have been developed
to extract cosmological information from the peculiar velocities in order to
test the cosmological models. These techniques include measuring cosmic flow,
measuring two-point correlation and power spectrum of the peculiar velocity
fields, reconstructing the density field using peculiar velocities. However,
some measurements from these techniques are biased due to the non-Gaussianity
of the estimated peculiar velocities. Therefore, we use the 2MTF survey to
explore a power transform that can Gaussianize the estimated peculiar
velocities. We find a tight linear relation between the transformation
parameters and the measurement errors of log-distance ratio. To show an example
for the implement of the Gaussianized peculiar velocities in cosmology, we
develop a bulk flow estimator and estimate bulk flow from the Gaussianized
peculiar velocities. We use 2MTF mocks to test the algorithm, we find the
algorithm yields unbiased measurements. We also find this technique gives
smaller measurement errors compared to other techniques. Under the Galactic
coordinates, at the depth of $30$ $h^{-1}$ Mpc, we measure a bulk flow of
$332pm27$ km s$^{-1}$ in the direction $(l,b)=(293pm 5^{circ}, 13pm
4^{circ})$. The measurement is consistent with the $Lambda$CDM prediction.
http://arxiv.org/icons/sfx.gif
