The Phantom Dark Matter Halos of the Local Volume in the Context of Modified Newtonian Dynamics

We explore the predictions of Milgromian gravity (MOND) in the local universe by considering the distribution of the phantom dark matter (PDM) that would source the MOND gravitational field in Newtonian gravity, allowing an easy comparison with the dark matter framework. For this, we specifically deal with the quasi-linear version of MOND (QUMOND). We compute the stellar-to-(phantom)halo mass relation (SHMR), a monotonically increasing power law resembling the SHMR observationally deduced from spiral galaxy rotation curves in the Newtonian context. We show that the gas-to-(phantom)halo mass relation is flat. We generate a map of the Local Volume in QUMOND, highlighting the important influence of distant galaxy clusters, in particular Virgo. This allows us to explore the scatter of the SHMR and the average density of PDM around galaxies in the Local Volume, omega(PDM) approximate to 0.1, below the average cold dark matter density in a ?CDM universe. We provide a model of the Milky Way in its external field in the MOND context, which we compare to an observational estimate of the escape velocity curve. Finally, we highlight the peculiar features related to the external field effect in the form of negative PDM density zones in the outskirts of each galaxy, and test a new analytic formula for computing galaxy rotation curves in the presence of an external field in QUMOND. While we show that the negative PDM density zones would be difficult to detect dynamically, we quantify the weak-lensing signal they could produce for lenses at z similar to 0.3.

Automated summary

The study explores the predictions of Milgromian gravity (MOND) in the local universe by considering the distribution of phantom dark matter (PDM) to enable comparison with the dark matter framework. The analysis focuses on the stellar-to-(phantom)halo mass relation (SHMR) in the quasi-linear version of MOND (QUMOND), showing a monotonically increasing power law shape. A map of the Local Volume is generated in QUMOND, emphasizing the influence of distant galaxy clusters, particularly Virgo. Additionally, a model of the Milky Way in the MOND context is provided, along with testing a new analytic formula for computing galaxy rotation curves in the presence of an external field in QUMOND.