Our galaxy, the Milky Way, belongs to a supercluster of galaxies known as Laniakea. The main goal of this project is to estimate its gravitational backreaction or, in other words, to understand how (if at all) the latter influences our Cosmological inference. We propose a toy model where Laniakea is described as a triaxially expanding homogeneous ellipsoid, with constant expansion rate along the principal axes. To build the model we use the CF4 reconstruction of the peculiar velocity field in the local Universe, and the recently update definition of Laniakea obtained from it. In this page you will find some of our results from this paper, and some supplementary material, including interactive plots, which did not fit there. I Hope you enjoy them!

Best fit Ellipsoid

The Ellipsoid which best fits Laniakea Surface:

Radial Velocities

The reconstructed radial peculiar velocity field inside Laniakea, computed with respect to the centre of our best fit ellipsoid:

Theoretical prediction

The quadrupolar prediction for the radial peculiar velocity field inside Laniakea predicted by the triaxial anisotropic expansion:

Residuals

The residuals, in units of standard deviations, between the reconstructed radial peculiar velocity field and the theoretical prediction for a constant dispersion of 170 km/s :

3D Corrections induced in Pantheon+

The relative corrections induced by our effective model on the luminosity distance of the Pantheon+ type Ia Supernovae used for the determination of the Hubble constant. The purple diamond indicates the position of the Milky Way

2D Corrections induced in Pantheon+

The relative corrections induced by our effective model on the luminosity distance of the Pantheon+ Supernovae used for the determination of the Hubble constant projected in the sky, as a function of RA and DEC. The size of the dots reflects their distance from the observer

2D Corrections induced on Surface Brightness Fluctuations

The relative corrections induced by our effective model on the luminosity distance of a sample of Surface Brightness Fluctuations projected in the sky, as a function of RA and DEC. The size of the dots reflects their distance from the observer