# 2M++ Density and Peculiar Velocity Fields

v1.0

• "Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field", Carrick J., Turnbull S., Lavaux G. & Hudson M. J., MNRAS, 2015. ADS

# Coordinates

The density and peculiar velocity fields are both 257 3 cubes using the same coordinate system: configuration ("real") space (reconstructed so that the peculiar velocities are removed iteratively as described in Carrick et al 15), and smoothed with a Guassian of scale 4 Mpc/h.

Specifically i,j,k index the 257 3 data cube in Galactic Cartesian comoving coordinates X,Y,Z in Mpc/h, with k running fastest. The cell centres run from -200 to 200 Mpc/h so the grid spacing is 1.5625 Mpc/h

To convert Galactic X,Y,Z use:

X = (i-128)*400./256.
Y = (j-128)*400./256.
Z = (k-128)*400./256.

The centre of the cell [0,0,0] therefore corresponds to -200,-200,-200 and the origin (Local Group) is in the centre of cell [128,128,128].

The density $$\delta_g^*$$ is the luminosity-weighted density contrast.

The velocities are predicted peculiar velocities in the CMB frame in Galactic Cartesian coordinates, generated from the $$\delta_g^*$$ field with $$\beta^* = 0.43$$ and an external dipole $$V_\mathrm{ext} = [89,-131,17]$$ (Carrick et al Table 3) has already been added.