Dearth of dark matter or massive dark halo? Mass-shape-anisotropy degeneracies revealed by NMAGIC dynamical models of the elliptical galaxy NGC 3379

Abstract

Recent results from the Planetary Nebula Spectrograph (PN.S) survey have revealed a rapidly falling velocity dispersion profile in the nearby elliptical galaxy NGC 3379, casting doubts on whether this intermediate-luminosity galaxy has the kind of dark matter halo expected in LambdaCDM cosmology. We present a detailed dynamical study of this galaxy, combining long-slit spectroscopy, SAURON integral-field data, and PN.S velocities, reaching to more than seven effective radii (R_e). We construct spherical and axisymmetric dynamical models for these data with the flexible made-to-measure NMAGIC code, in a sequence of gravitational potentials with varying dark halo mass. We find that the data are consistent both with near-isotropic spherical systems dominated by the stellar mass, and with models in massive halos with strongly radially anisotropic outer parts (beta >~ 0.8 at 7R_e). Formal likelihood limits would exclude (at 1 sigma) the model with stars only, as well as halo models with v_circ(7R_e) >~ 250 km/s. A sequence of more realistic axisymmetric models of different inclinations and a small number of triaxial tests confirm the spherical results. All valid models fitting all the data are dynamically stable over Gyrs, including the most anisotropic ones. NGC 3379 may well have a dark matter halo as predicted by recent merger models within LambdaCDM cosmology, provided its outer envelope is strongly radially anisotropic. (abridged)

22 pages, 25 figures, revised version for MNRAS

References in corpus (7)

• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• Kinematic properties of early-type galaxy haloes using planetary nebulae
• Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies
• NMAGIC: Fast Parallel Implementation of a Chi-Squared-Made-to-Measure Algorithm for Modelling Observational Data
• Dark matter content and internal dynamics of NGC 4697: NMAGIC particle models from slit data and planetary nebulae velocities
• The Black Hole in NGC 3379: A Comparison of Gas and Stellar Dynamical Mass Measurements with HST and Integral-Field Data
• Constraining the Mass Profiles of Stellar Systems: Schwarzschild Modeling of Discrete Velocity Datasets

Cited by in corpus (30)

• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• The SAGES Legacy Unifying Globulars and GalaxieS Survey (SLUGGS): Sample definition, methods, and initial results
• Made-to-Measure models of the Galactic Box/Peanut bulge: stellar and total mass in the bulge region
• The PN.S Elliptical Galaxy Survey: the dark matter in NGC 4494
• The MASSIVE Survey - V. Spatially-Resolved Stellar Angular Momentum, Velocity Dispersion, and Higher Moments of the 41 Most Massive Local Early-Type Galaxies
• Small scatter and nearly-isothermal mass profiles to four half-light radii from two-dimensional stellar dynamics of early-type galaxies
• Sloshing in its cD halo: MUSE kinematics of the central galaxy NGC 3311
• Counter-dispersed slitless-spectroscopy technique: planetary nebula velocities in the halo of NGC 1399
• A discrete chemo-dynamical model of the giant elliptical galaxy NGC 5846: dark matter fraction, internal rotation and velocity anisotropy out to six effective radii
• Dynamical model of the Milky Way using APOGEE and Gaia data
• Discovery of Hot Gas in Outflow in NGC3379
• Kinematics of the diffuse intragroup and intracluster light in groups and clusters of galaxies in the Local Universe within 100 Mpc distance
• Dark Matter Density Profiles in Dwarf Galaxies: Linking Jeans Modeling Systematics and Observation
• The halo of M105 and its group environment as traced by planetary nebula populations: I. Wide-field photometric survey of planetary nebulae in the Leo I group
• Dark Matter Deprivation in Field Elliptical Galaxy NGC 7507
• The halo of M105 and its group environment as traced by planetary nebula populations: II. Using kinematics of single stars to unveil the presence of intragroup light around the Leo I galaxies NGC 3384 and M105
• New constraints on the central mass contents of Omega Centauri from combined stellar kinematics and pulsar timing
• The Fornax Cluster VLT Spectroscopic Survey IV -- Cold kinematical substructures in the Fornax core from COSTA
• The proper motion of stars in dwarf galaxies: distinguishing central density cusps from cores
• Basis function expansions for galactic dynamics: Spherical versus cylindrical coordinates
• Andromeda XXV -- a dwarf galaxy with a low central dark matter density
• Made-To-Measure Models of Self-Similar Triaxial Halos with Steep Inner Density Gradients
• Trial by FIRE: Probing the dark matter density profile of dwarf galaxies with GraphNPE
• GravSphere2: A higher-order Jeans method for mass-modeling spherical stellar systems
• HST Hα grism spectroscopy of ROLES: a flatter low-mass slope for the z~1 SSFR--mass relation
• Made-to-Measure Modelling of Globular Clusters
• The isolated elliptical galaxy NGC 5812 -- MOND or Dark Matter?
• COSTA: the COld STream finder Algorithm. Searching for kinematical substructures in the phase space of discrete tracers
• Kinematics of planetary nebulae in the outskirts of the elliptical galaxy NGC 4697