Additional velocity Distribution: A fast sample analysis for dark matter or modified gravity models

Abstract: We propose a new complementary and fast approach to study galaxy rotation curves straight from the sample data, instead of individual rotation curve fits. It is based on the difference between the observational rotation curve and the expected one from the baryonic matter, under certain normalization (𝛿𝑉2). The first step is to find the observational data distribution of 𝛿𝑉2, which is estimated from the observational data from a 2D kernel density estimation. The estimate is then contrasted with specific model predictions for the same baryonic data. Here we consider the following five models: Burkert profile, MOND, Palatini 𝑓(𝑅) gravity, Eddington-inspired-Born-Infeld (EiBI) model and general relativity with renormalization group effects (RGGR). We stress the following method properties: i) the method deals with the sample behaviour, not the individual galaxy fits: it provides quicker evaluation and it promptly presents sample properties; ii) it studies the form of the velocity curve added by the model, not its magnitude (typically, this implies one less parameter for the analysis); iii) it can be applied to modified gravity models even if the observational 3D baryonic matter distribution is not known: it is based on the baryonic velocity contribution to the rotation curve together with minimal hypothesis on the average 3D modeling. About the tested models, and considering the tests that the method can perform, the Burkert profile, MOND and RGGR have good sample behaviour, nonetheless, the method points out specific difficulties for these three cases. Palatini 𝑓(𝑅) and EiBI gravities cannot be used to replace dark matter and, if considered together with some dark matter halo, large amounts of the latter will be necessary.

astrophysicscondensed mattergeneral relativity and quantum cosmologyhigh energy physicsmathematical physicsclassical physicsgeneral physics

Audience: researchers in the topic

Theoretical physics seminar @ Tartu