Micro galaxies in LCDM

Abstract

A fundamental prediction of the Lambda Cold Dark Matter (LCDM) cosmology is the centrally divergent cuspy density profile of dark matter haloes. Density cusps render CDM haloes resilient to tides, and protect dwarf galaxies embedded in them from full tidal disruption. The hierarchical assembly history of the Milky Way may therefore give rise to a population of micro galaxies; i.e., heavily stripped remnants of early accreted satellites, which may reach arbitrarily low luminosity. Assuming that the progenitor systems are dark matter dominated, we use an empirical formalism for tidal stripping to predict the evolution of the luminosity, size, and velocity dispersion of such remnants, tracing their tidal evolution across multiple orders of magnitude in mass and size. The evolutionary tracks depend sensitively on the progenitor distribution of stellar binding energies. We explore three cases that likely bracket most realistic models of dwarf galaxies: one where the energy distribution of the most tightly bound stars follows that of the dark matter, and two where stars are defined by either an exponential density or surface brightness profile. The tidal evolution in the size-velocity dispersion plane is quite similar for these three models, although their remnants may differ widely in luminosity. Micro galaxies are therefore best distinguished from globular clusters by the presence of dark matter; either directly, by measuring their velocity dispersion, or indirectly, by examining their tidal resilience. Our work highlights the need for further theoretical and observational constraints on the stellar energy distribution in dwarf galaxies.

updated to match accepted version

References in corpus (19)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Hundreds of Milky Way Satellites? Luminosity Bias in the Satellite Luminosity Function
• The Tidal Evolution of Local Group Dwarf Spheroidals
• Dark matter and cosmic structure
• Disruption of Dark Matter Substructure: Fact or Fiction?
• Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies
• Dark Matter Substructure in Numerical Simulations: A Tale of Discreteness Noise, Runaway Instabilities, and Artificial Disruption
• Scaling Relations and the Fundamental Line of the Local Group Dwarf Galaxies
• Kinematics of Antlia 2 and Crater 2 from The Southern Stellar Stream Spectroscopic Survey (S5)
• Testing Fundamental Physics with Distant Star Clusters: Analysis of Observational Data on Palomar 14
• An extended halo around an ancient dwarf galaxy
• The effect of a disc on the population of cuspy and cored dark matter substructures in Milky Way-like galaxies
• A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies
• Palomar 5 and its Tidal Tails: A Search for New Members in the Tidal Stream
• What sets the central structure of dark matter haloes?
• The tangential velocity excess of the Milky Way satellites
• Ursa Major III/UNIONS 1: the darkest galaxy ever discovered?
• The Normalization and Slope of the Dark Matter (Sub-)Halo Mass Function on Sub-Galactic Scales
• A novel JEAnS analysis of the Fornax dwarf using evolutionary algorithms: mass follows light with signs of an off-centre merger

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• Stellar Mass Segregation in Dark Matter Halos
• Dark Star Clusters or Ultra-Faint Dwarf galaxies? Revisiting UMa3/U1
• Ultra-Faint Milky Way Satellites Discovered in Carina, Phoenix, and Telescopium with DELVE Data Release 3
• A Relativistic Scalar Model for Fractional Interaction between Dark Matter and Gravity
• Collisional Dynamics of Stars and Dark Matter in Ultra-Faint Galaxies