MOA-II Galactic Microlensing Constraints: The Inner Milky Way has a Low Dark Matter Fraction and a Near Maximal Disk

Abstract

Microlensing provides a unique tool to break the stellar to dark matter degeneracy in the inner Milky Way. We combine N-body dynamical models fitted to the Milky Way's Boxy/Peanut bulge with exponential disk models outside this, and compute the microlensing properties. Considering the range of models consistent with the revised MOA-II data, we find low dark matter fractions in the inner Galaxy: at the peak of their stellar rotation curve a fraction $f_v=(0.88\pm 0.07)$ of the circular velocity is baryonic (at $1\sigma$, $f_v>0.72$ at $2\sigma$). These results are in agreement with constraints from the EROS-II microlensing survey of brighter resolved stars, where we find $f_v=(0.9\pm 0.1)$ at $1\sigma$. Our fiducial model of a disk with scale length 2.6kpc, and a bulge with a low dark matter fraction of 12%, agrees with both the revised MOA-II and EROS-II microlensing data. The required baryonic fractions, and the resultant low contribution from dark matter, are consistent with the NFW profiles produced by dissipationless cosmological simulations in Milky Way mass galaxies. They are also consistent with recent prescriptions for the mild adiabatic contraction of Milky Way mass haloes without the need for strong feedback, but there is some tension with recent measurements of the local dark matter density. Microlensing optical depths from the larger OGLE-III sample could improve these constraints further when available.

14 pages, 13 figures, submitted to MNRAS

References in corpus (17)

• Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds
• Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 results
• The Local Dark Matter Density
• Baryon effects on the internal structure of LCDM halos in the EAGLE simulations
• The Structure of the Milky Way's Bar Outside the Bulge
• A Revised Model for the Formation of Disk Galaxies: Low Spin and Dark-Halo Expansion
• The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass
• Constraining the Galaxy's dark halo with RAVE stars
• Made-to-Measure models of the Galactic Box/Peanut bulge: stellar and total mass in the bulge region
• Weighing Galaxy Disks with the Baryonic Tully-Fisher Relation
• Weighing the local dark matter with RAVE red clump stars
• Evidence for a Turnover in the IMF of Low Mass Stars and Sub-stellar Objects: Analysis from an Ensemble of Young Clusters
• OGLE-III Microlensing Events and the Structure of the Galactic Bulge
• Microlensing constraints on the Galactic Bulge Initial Mass Function
• Modeling the Gas Flow in the Bar of NGC 1365
• Bringing the Galaxy's dark halo to life
• Microlensing optical depth as a function of source apparent magnitude

Cited by in corpus (16)

• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• No large population of unbound or wide-orbit Jupiter-mass planets
• The shape of the inner Milky Way halo from observations of the Pal 5 and GD-1 stellar streams
• Detection of the Keplerian decline in the Milky Way rotation curve
• A centrally heated dark halo for our Galaxy
• A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data
• Testing Bose-Einstein Condensate dark matter models with the SPARC galactic rotation curves data
• The Initial Mass Function of the Inner Galaxy Measured From OGLE-III Microlensing Timescales
• The structural evolution of galaxies with both thin and thick discs
• Migration and kinematics in growing disc galaxies with thin and thick discs
• 7.1 keV sterile neutrino dark matter constraints from a deep Chandra X-ray observation of the Galactic bulge Limiting Window
• Which Milky Way masses are consistent with the slightly declining 5-25 kpc rotation curve?
• A microlensing search of 700 million VVV light curves
• VVV Survey Microlensing: the Galactic Latitude Dependence
• Constraining the environment of compact binary mergers with self-lensing signatures
• The odd primordial halo of the Milky Way implied by Gaia. A shallow core, but a steep decline