Densities and mass assembly histories of the Milky Way satellites are not a challenge to $\Lambda$CDM

Abstract

We use the \texttt{GRUMPY} galaxy formation model based on a suite of zoom-in, high-resolution, dissipationless $\Lambda$ Cold Dark Matter ($\Lambda$CDM) simulations of the Milky Way (MW) sized haloes to examine total matter density within the half-mass radius of stellar distribution, ${\rho }_{\mathrm{tot}}(<r_{1/2})$, of satellite dwarf galaxies around the MW hosts and their mass assembly histories. We compare model results to ${\rho }_{\mathrm{tot}}(<r_{1/2})$ estimates for observed dwarf satellites of the Milky Way spanning their entire luminosity range. We show that observed MW dwarf satellites exhibit a trend of decreasing ${\rho }_{\mathrm{tot}}(<r_{1/2})$ with increasing stellar mass. This trend is in general agreement with the trend predicted by the model. None of the observed satellites are overly dense compared to the results of our $\Lambda$CDM-based model. We also show that although the halo mass of many satellite galaxies is comparable to the halo mass of the MW progenitor at $z>10$, at these early epochs halos that survive as satellites to $z=0$ are located many virial radii away from the MW progenitors and thus do not have a chance to merge with it. Our results show that neither the densities estimated in observed Milky Way satellites nor their mass assembly histories pose a challenge to the $\Lambda$CDM model. In fact, the broad agreement between density trends with the stellar mass of the observed and model galaxies can be considered as yet another success of the model.

arXiv comment9 pages, 4 figures, 1 table. Submitted to MNRAS

References in corpus (70)

• The NumPy array: a structure for efficient numerical computation
• A Universal Density Profile from Hierarchical Clustering
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Small-Scale Challenges to the $\Lambda$CDM Paradigm
• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Gas-regulation of galaxies: the evolution of the cosmic sSFR, the metallicity-mass-SFR relation and the stellar content of haloes
• Accurate masses for dispersion-supported galaxies
• A Universal Mass Profile for Dwarf Spheroidal Galaxies?
• Gravitationally Consistent Halo Catalogs and Merger Trees for Precision Cosmology
• The Faintest Dwarf Galaxies
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The unexpected diversity of dwarf galaxy rotation curves
• High-resolution mass models of dwarf galaxies from LITTLE THINGS
• The size - virial radius relation of galaxies
• Dark matter cores all the way down
• Stellar mass -- halo mass relation and star formation efficiency in high-mass halos
• NIHAO IV: Core creation and destruction in dark matter density profiles across cosmic time
• A Complete Spectroscopic Survey of the Milky Way Satellite Segue 1: The Darkest Galaxy
• The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater
• Milky Way Satellite Census. II. Galaxy--Halo Connection Constraints Including the Impact of the Large Magellanic Cloud
• A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters
• Metallicity-Dependent quenching of Star Formation at High Redshift in Small Galaxies
• A dark matter profile to model diverse feedback-induced core sizes of $\Lambda$CDM haloes
• Farthest Neighbor: The Distant Milky Way Satellite Eridanus II
• Segue 2: The Least Massive Galaxy
• Willman 1 - a probable dwarf galaxy with an irregular kinematic distribution
• The Relationship between Galaxy and Dark Matter Halo Size from z~3 to the present
• Spectroscopic Confirmation of the Dwarf Galaxies Hydra II and Pisces II and the Globular Cluster Laevens 1
• Discovery of two neighboring satellites in the Carina constellation with MagLiteS
• Proper Motions, Orbits, and Tidal Influences of Milky Way Dwarf Spheroidal Galaxies
• The Caterpillar Project: A Large Suite of Milky Way Sized Halos
• The detailed structure and the onset of galaxy formation in low-mass gaseous dark matter haloes
• Snake in the Clouds: A new nearby dwarf galaxy in the Magellanic bridge
• At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data
• Systematics in virial mass estimators for pressure-supported systems
• Too Big To Fail in Light of Gaia
• Kinematics of Antlia 2 and Crater 2 from The Southern Stellar Stream Spectroscopic Survey (S5)
• A Deeper Look at the New Milky Way Satellites: Sagittarius II, Reticulum II, Phoenix II, and Tucana III
• Two Ultra-Faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey
• Pristine Dwarf-Galaxy Survey I: A detailed photometric and spectroscopic study of the very metal-poor Draco II satellite
• Abundance matching with the mean star formation rate: there is no missing satellites problem in the Milky Way above ${\mathbf{M}}_{200}\sim 10^9{\mathbf{M}}_{\odot }$
• Phase Space Models of the Dwarf Spheroidal Galaxies
• Half-mass radii of quiescent and star-forming galaxies evolve slowly from 0 < z < 2.5: implications for galaxy assembly histories
• Birds of a Feather? Magellan/IMACS Spectroscopy of the Ultra-Faint Satellites Grus II, Tucana IV, and Tucana V
• Comparison of an approximately isothermal gravitational potentials of elliptical galaxies based on X-ray and optical data
• Knowing the unknowns: uncertainties in simple estimators of galactic dynamical masses
• Ships Passing in the Night: Spectroscopic Analysis of Two Ultra-Faint Satellites in the Constellation Carina
• On the dynamics of the Small Magellanic Cloud through high-resolution ASKAP HI observations
• Kinematics and Metallicities in the Bootes III Stellar Overdensity: a Disrupted Dwarf Galaxy?
• Portrait of a Dark Horse: a Photometric and Spectroscopic Study of the Ultra-faint Milky Way Satellite Pegasus III
• A Gaia DR 2 and VLT/FLAMES search for new satellites of the LMC
• Motivations for a Large Self-Interacting Dark Matter Cross Section from Milky Way Satellites
• Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-Faint Dwarf Galaxy in the Constellation Pegasus
• VLT Spectroscopy of Ultra-Faint Dwarf Galaxies. 1. Boötes I, Leo IV, Leo V
• The Pristine Dwarf-Galaxy survey - II. In-depth observational study of the faint Milky Way satellite Sagittarius II
• GRUMPY: a simple framework for realistic forward-modelling of dwarf galaxies
• A multi-epoch kinematic study of the remote dwarf spheroidal galaxy Leo II
• Starbursts in low-mass haloes at Cosmic Dawn. I. The critical halo mass for star formation
• Lessons from cosmic history: The case for a linear star formation -- H2 relation
• Bootes III is a disrupting dwarf galaxy associated with the Styx stellar stream
• The Pristine Dwarf-Galaxy survey -- III. Revealing the nature of the Milky Way globular cluster Sagittarius II
• Detailed chemical abundances of stars in the outskirts of the Tucana II ultra-faint dwarf galaxy
• Dwarf Galaxy Mass Estimators vs. Cosmological Simulations
• A Deeper Look at DES Dwarf Galaxy Candidates: Grus I and Indus II
• Red Clump stars in the Bootes III stellar system
• Spatial and orbital planes of the Milky Way satellites: unusual but consistent with $\Lambda$CDM
• Stellar kinematics of dwarf galaxies from multi-epoch spectroscopy: application to Triangulum II
• Milky Way satellite velocities reveal the Dark Matter power spectrum at small scales