Velocity field derived from 2MASS Redshift Survey

In Lavaux, Tully, Mohayaee & Colombi (2008, MNRAS), we have derived the 3d peculiar velocities of galaxies of the 2MASS Redshift Survey using a dynamical model. This velocities can be used to make corrections to observed redshifts and/or derived absolute magnitudes for galaxies in other surveys.

In this page, I am making available an adaptively smoothed version of this peculiar velocities. I also include python scripts to derive line-of-sight peculiar velocities within the volume where velocities have been reconstructed (in that case a sphere of 100 Mpc/h) centered on the Local Group).

Bundled files

  • vr.nc is a data cube holding the velocity field (NetCDF format)
  • pupynere.py is a python module for accessing NetCDF files (original package is http://pypi.python.org/pypi/pupynere/). It is required by vel_model.py
  • vel_model.py exports one function: “compute_vr(cz, l, b)”. It returns the velocity field in the rest frame of the Local Sheet (see Tully & al, 2008, ApJ for the relationship with the Local Group rest frame). cz must also be provided in the rest frame of the Local Sheet. “l” and “b” are in Galactic coordinates.
  • demo.py is a simple program to show how to call this function

Please note: these are files compatible with Python 2.x and not Python 3.x.

Download link

These files may be downloaded from VelocityModel_2MRS.tar.gz.

Velocity field pictures

I am showing below the view of the velocity field and the underlying density field in supergalactic coordinates. The left panel is a zoom on the central part of the right panel. The Virgo cluster is clearly seen as the central red blob. Most of the matter is infalling in the direction of the Great Attractor which represented by the crowded green region.

Usage policy

If you use this velocity field please cite our paper:
“Cosmic Flow From Two Micron All-Sky Redshift Survey: the Origin of Cosmic Microwave Background Dipole and Implications for ΛCDM Cosmology”; Lavaux, G.; Tully, R. B.; Mohayaee, R.; Colombi, S.; The Astrophysical Journal, Volume 709, Issue 1, pp. 483-498 (2010); arXiV:0810.3658

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