Constraining the Milky Way Mass profile with data driven distribution function using DESI DR2 halo stars

Abstract

We employ a novel data-driven dynamical modeling method, the empirical distribution function (emPDF), to constrain the Milky Way mass profile using a large sample of halo stars from the Dark Energy Spectroscopic Instrument Milky Way Survey (DESI MWS). The method does not assume any functional form of the tracer distribution. Deviations from the steady-state assumption and the effects of observational errors are further tested and calibrated using a number of realistic mock observations (AuriDESI). Applying the calibrated method to two classes of tracers in DESI, we derive a best-constrained virial mass and concentration of $\log M_{200c}/M_{\odot }=12.05_{-0.12}^{+0.21}{(}_{-0.18}^{+0.26})$ and $\log c_{200c}=1.20_{-0.16}^{+0.11}{(}_{-0.24}^{+0.20})$ for BHBs. For RR Lyrae stars we derive $\log M_{200c}/M_{\odot }=12.15_{-0.14}^{+0.22}{(}_{-0.19}^{+0.26})$ and $\log c_{200c}=1.16_{-0.12}^{+0.09}{(}_{-0.18}^{+0.16})$. The uncertainties quoted outside and within brackets are statistical and total errors including systematic errors calibrated from AuriDESI, respectively. The two tracer populations provide overall consistent measurements of the MW halo mass profile. Combining the halo star constraints with the independent constraint from satellite dynamics, we derive a robust and precise final measurement of the MW halo parameters of $\log M_{200c}/M_{\odot }=12.12_{-0.05}^{+0.05}{(}_{-0.04}^{+0.06})$ and $\log c_{200c}=1.16_{-0.03}^{+0.05}{(}_{-0.07}^{+0.05})$, with correlation coefficients of $\rho =-0.90(-0.54)$.

arXiv comment23 pages, 11 figures. This paper is a DESI Collaboration Key Project publication