http://arxiv.org/abs/2210.07230
Rotation curves are the key observational manifestation of the dark matter distribution around late-type galaxies. In a halo model context, the precision of constraints on halo parameters is a complex function of the properties of the measurements as well as properties of the galaxy itself. Forthcoming surveys will resolve rotation curves to varying degrees of precision, or measure their integrated effect in the HI linewidth. To ascertain the relative significance of the relevant quantities for constraining halo properties, we study the information on halo mass and concentration as quantified by the Kullback-Leibler divergence of the kinematics-informed posterior from the uninformative prior. We calculate this divergence as a function of the different types of spectroscopic observation, properties of the measurement, galaxy properties and auxiliary observational data on the baryonic components. Using the SPARC sample, we find that fits to the full rotation curve exhibit a large variation in information gain between galaxies, ranging from 1 to 11 bits. This range is equivalent to the difference between the prior shrinking to a flat posterior that is only a factor of 2 smaller compared to a factor of 2000 smaller. It is predominantly caused by the vast differences in the number of data points and the size of velocity uncertainties between the SPARC galaxies. Out of the galaxy properties, only the degree of dark matter dominance is important. We also study the relative importance of the minimum HI surface density probed and the size of velocity uncertainties on the constraining power on the inner halo slope, finding the latter to be significantly more important. We spell out the implications of these results for optimising the strategy of galaxy surveys aiming to constrain galaxies’ dark matter distributions, highlighting spectroscopic precision as the most important factor.
T. Yasin, H. Desmond, J. Devriendt, et. al.
Fri, 14 Oct 22
28/75
Comments: 13 pages, 7 figures
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