Polytropic spheres modelling dark matter halos of dwarf galaxies

Abstract

Dwarf galaxies and their dark matter (DM) halos have the velocity curves of a different character than those in large galaxies. They are modelled by a simple pseudo iso-thermal model containing only two parameters that do not allow to obtain insight into physics of the DM halo. We would like to obtain some insight into the physical conditions in DM halos of dwarf galaxies by using a simple physically based model of DM halos. In order to treat a diversity of the dwarf galaxy velocity profiles in a unifying framework, we apply the polytropic spheres characterised by the polytropic index $n$ and the relativistic parameter $\sigma$ as a model of dwarf-galaxy DM halos and match the velocity of circular geodesics of the polytropes to the velocity curves observed in the dwarf galaxies from the LITTLE THINGS ensemble. We introduce three classes of the LITTLE THINGS dwarf galaxies in accord with the polytrope models, due to the different character of the velocity profile. The first class corresponds to polytropes having $n<1$ with linearly increasing velocity along with the whole profile, the second class has $1<n<2$ and the velocity profile becomes flat in the external region, the third class has $n>2$ and the velocity profile reaches a maximum and demonstrated a decline in the external region. The $\sigma$ parameter has to be strongly non-relativistic ($\sigma <10^{-8}$) for all dwarf galaxy models -- it varies for the models of each class, but these variations have a negligible influence on the character of the velocity profile. Our results indicate the possibility that at least two different kinds of dark matter are behind the composition of DM halos. The matches of the observational velocity curves are of the same quality as those obtained by the pseudo-isothermal, core-like models of dwarf galaxy DM halos.

arXiv commentAccepted for publication in Astronomy and Astrophysics

References in corpus (51)

• A Universal Density Profile from Hierarchical Clustering
• Gaia Data Release 2. Summary of the contents and survey properties
• Dark Matter Substructure in Galactic Halos
• Profiles of dark haloes: evolution, scatter, and environment
• Observational evidence for self-interacting cold dark matter
• Cold and Fuzzy Dark Matter
• Ultralight scalars as cosmological dark matter
• Neutron Star Structure and the Equation of State
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Cosmic Structure as the Quantum Interference of a Coherent Dark Wave
• How supernova feedback turns dark matter cusps into cores
• Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies
• H alpha rotation curves of Low Surface Brightness galaxies
• Cusp-core transformations in dwarf galaxies: observational predictions
• Mass loss from dwarf spheroidal galaxies: the origins of shallow dark matter cores and exponential surface brightness profiles
• The haloes of bright satellite galaxies in a warm dark matter universe
• High-resolution mass models of dwarf galaxies from LITTLE THINGS
• Fluid Dark Matter
• Stellar Feedback in Dwarf Galaxy Formation
• In disguise or out of reach: first clues about in-situ and accreted stars in the stellar halo of the Milky Way from Gaia DR2
• Core Formation in Dwarf Halos with Self Interacting Dark Matter: No Fine-Tuning Necessary
• Dark matter cores all the way down
• (Star)bursts of FIRE: observational signatures of bursty star formation in galaxies
• Dark matter heats up in dwarf galaxies
• Broad-Band Imaging of a Large Sample of Irregular Galaxies
• Reconstructing the Neutron-Star Equation of State from Astrophysical Measurements
• Influence of the relict cosmological constant on accretion discs
• General Relativistic Stars : Polytropic Equations of State
• The Resolved Structure and Dynamics of an Isolated Dwarf Galaxy: A VLT and Keck Spectroscopic Survey of WLM
• Light escape cones in local reference frames of Kerr-de Sitter black hole spacetimes and related black hole shadows
• The no-spin zone: rotation vs dispersion support in observed and simulated dwarf galaxies
• General relativistic polytropes with a repulsive cosmological constant
• High-mass twin stars with a multi-polytrope EoS
• Deep HST Imaging of Sextans A I. The Spatially Resolved Recent Star Formation History
• Eleven spherically symmetric constant density solutions with cosmological constant
• The Aptly Named Phoenix Dwarf Galaxy
• Turnaround radius in an accelerated universe with quasi-local mass
• Gravitational instability of polytropic spheres containing region of trapped null geodesics: a possible explanation of central supermassive black holes in galactic halos
• The Galactic Halo in Mixed Dark Matter Cosmologies
• Galaxy cluster lensing masses in modified lensing potentials
• Polytropic spheres containing regions of trapped null geodesics
• Cold or Warm? Constraining Dark Matter with Primeval Galaxies and Cosmic Reionization after Planck
• Constraining self-interacting dark matter with scaling laws of observed halo surface densities
• Charged reflecting stars supporting charged massive scalar field configurations
• Dwarf Galaxies in the Coma Cluster: I. Velocity Dispersion Measurements
• Perfect fluid spheres with cosmological constant
• Photon and neutrino redshift in the field of braneworld compact stars
• The Komar mass function in the de-Rham-Gabadadze-Tolley non-linear theory of massive gravity
• The Fundamental Line of the Local Group Satellites
• Connecting the local stellar halo and its dark matter density to dwarf galaxies via blue stragglers

Cited by in corpus (9)

• Confront $f(R,T)=\mathcal{R}+\beta T$ modified gravity with the massive pulsar PSR J0740+6620
• Extended Tolman III and VII solutions in $f(\mathcal{R},T)$ gravity: Models for neutron stars and supermassive stars
• Complexity factor of spherically anisotropic polytropes from gravitational decoupling
• Gravitational Cracking of General Relativistic Polytropes: a generalized scheme
• Double relativistic master polytrope for anisotropic matter
• Dark matter halos modeled by polytropic spheres influenced by the relict cosmological constant and trapping polytropes forming supermassive black holes
• Physically motivated fit to mass surface density profiles observed in galaxies
• Halo structure and lensing signatures of a polytropic dark matter fluid
• Static Charged Polytropic Spheres with a Cosmological Constant: Physical Acceptability and Trapped Orbits