The core-cusp problem : a matter of perspective

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Genina , A , Benitez-Llambay , A , Frenk , C S , Cole , S , Fattahi , A , Navarro , J F , Oman , K A , Sawala , T & Theuns , T 2018 , ' The core-cusp problem : a matter of perspective ' , Monthly Notices of the Royal Astronomical Society , vol. 474 , no. 1 , pp. 1398-1411 . https://doi.org/10.1093/mnras/stx2855

Title: The core-cusp problem : a matter of perspective
Author: Genina, Anna; Benitez-Llambay, Alejandro; Frenk, Carlos S.; Cole, Shaun; Fattahi, Azadeh; Navarro, Julio F.; Oman, Kyle A.; Sawala, Till; Theuns, Tom
Other contributor: University of Helsinki, Department of Physics
Date: 2018-02
Language: eng
Number of pages: 14
Belongs to series: Monthly Notices of the Royal Astronomical Society
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stx2855
URI: http://hdl.handle.net/10138/233186
Abstract: The existence of two kinematically and chemically distinct stellar subpopulations in the Sculptor and Fornax dwarf galaxies offers the opportunity to constrain the density profile of their matter haloes by measuring the mass contained within the well-separated half-light radii of the two metallicity subpopulations. Walker and Penarrubia have used this approach to argue that data for these galaxies are consistent with constant-density 'cores' in their inner regions and rule out 'cuspy' Navarro-Frenk-White (NFW) profiles with high statistical significance, particularly in the case of Sculptor. We test the validity of these claims using dwarf galaxies in the APOSTLE (A Project Of Simulating The Local Environment) Lambda cold dark matter cosmological hydrodynamic simulations of analogues of the Local Group. These galaxies all have NFW dark matter density profiles and a subset of them develop two distinct metallicity subpopulations reminiscent of Sculptor and Fornax. We apply a method analogous to that of Walker and Penarrubia to a sample of 50 simulated dwarfs and find that this procedure often leads to a statistically significant detection of a core in the profile when in reality there is a cusp. Although multiple factors contribute to these failures, the main cause is a violation of the assumption of spherical symmetry upon which the mass estimators are based. The stellar populations of the simulated dwarfs tend to be significantly elongated and, in several cases, the two metallicity populations have different asphericity and are misaligned. As a result, a wide range of slopes of the density profile are inferred depending on the angle from which the galaxy is viewed.
Subject: galaxies: dwarf
galaxies: formation
galaxies: kinematics and dynamics
dark matter
COLD DARK-MATTER
DWARF SPHEROIDAL GALAXY
COSMOLOGICAL SIMULATIONS
DYNAMICAL FRICTION
EAGLE SIMULATIONS
DENSITY PROFILES
HALOES
FEEDBACK
EVOLUTION
UNIVERSE
115 Astronomy, Space science
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