Dark energy Constraints from different Local Group Histories
Abstract
The dynamics of the Local Group (LG), especially concerning the contributions of the Milky Way (MW) and Andromeda (M31) galaxies, is sensitive to the presence of dark energy. This work compares the evolution of the LG by considering it as a twobody problem in a homogeneous and isotropic expanding spacetime, i.e. the McVitte spacetime (McV) versus the spherically symmetric metric for LG dynamics with the Cosmological Constant, i.e. the De SitterSchwarzschild spacetime (DsS). Using the Timing Argument (which links LG dynamics to LG mass), calibrated by the IllustrisTNG simulations, we find that the McV spacetime predicts a lower mass for the LG: $\left(4.20 \pm 0.61\right) \cdot 10^{12} M_{\odot}$ for McV spacetime vs. $\left(4.65 \pm 0.75\right) \cdot 10^{12} M_{\odot}$ for DsS spacetime ($68 \% ,$ CL). Due to uncertainties in tangential velocity measurements, the masses are indistinguishable. However, with future astrometric measurements, we demonstrate that the predicted masses will be distinguishable, indicating different LG histories. By independently estimating the total mass of MW and M31, we compare the possible upper bounds for the Cosmological Constant in these scenarios. We find a tighter upper bound for the DsS spacetime model, $\Lambda < 3.3 \,\Lambda_{\text{CMB}}$, compared to $\Lambda < 8.4\, \Lambda_{\text{CMB}}$ for the McV spacetime (where $\Lambda_{\text{CMB}}$ is the mean value from Planck). Future astrometric measurements, such as those from JWST, hold the potential to independently detect dark energy for both spacetime models independent from Planck's value.
 Publication:

arXiv eprints
 Pub Date:
 January 2024
 DOI:
 10.48550/arXiv.2401.09546
 arXiv:
 arXiv:2401.09546
 Bibcode:
 2024arXiv240109546B
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Solar and Stellar Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 6 pages