The Spin Alignments in Galaxy Pairs as a Test of Bouncing Coupled Dark Energy

TL;DR

This study examines how coupled dark energy models, especially bouncing cDE, influence galaxy pair spin alignments, revealing a significant alignment signal only in the bouncing cDE model, thus providing a potential test for such theories.

Contribution

It demonstrates that spin alignments in galaxy pairs can serve as a unique observational test for bouncing coupled dark energy models, distinguishing them from other cosmologies.

Findings

SUGRA003 bouncing cDE model shows strong spin alignment signals.

Standard LCDM and other cDE models exhibit weak or no signals.

Spin alignment strength is independent of galaxy pair mass and separation.

Abstract

We investigate the effect of coupled dark energy (cDE) on the spin alignments in isolated pairs of galactic halos, using the publicly available data from the hydrodynamical cDE simulations (H-CoDECs) which were run for various cDE models such as EXP001, EXP002, EXP003 (with exponential potential and constant coupling), EXP008e3 (with exponential potential and exponential coupling) and SUGRA003 (with supergravity potential and negative constant coupling) as well as for a standard LCDM cosmology (with the WMAP7 parameters). Measuring the cosines of the angles between the spin axes in isolated pairs of galactic halos for each model and determining its probability density distribution, we show that for the SUGRA003 model with bouncing cDE the null hypothesis of no spin alignment in pairs of galactic halos is rejected at 99.999% confidence level. In contrast, the LCDM cosmology yields no significant signal of spin alignment and the other four cDE models also exhibit only weak signals of spin-alignments. The strength of the spin alignment signal is found to be almost independent of the total halo mass and separation distance in galaxy pairs. Showing also that no signal is detected from the Sloan Digital Sky Survey DR 7, we conclude that the spin alignments in galaxy pairs is in principle a unique test of bouncing cDE models.