The Impact of Molecular Hydrogen Cooling on the Galaxy Formation Threshold

Abstract

We study the impact of molecular (${\mathrm{H}}_2$) and atomic (HI) hydrogen cooling on the galaxy formation threshold. We calculate the fraction of dark matter (DM) halos that exceeds a critical mass required for star formation, $M_{\mathrm{crit}}(z)$, as a function of their peak mass. By convolving analytic halo mass accretion histories (MAHs) with models for $M_{\mathrm{crit}}(z)$, we predict that halos with peak virial masses below $\sim 10^8{M}_{\odot }$ can form stars before reionization through ${\mathrm{H}}_2$ cooling. These halos remain dark when only HI cooling and reionization are modeled. However, less than $\approx 10\%$ of halos with peak masses below $\sim 10^7{M}_{\odot }$ ever exceed $M_{\mathrm{crit}}(z)$, even when ${\mathrm{H}}_2$ cooling is included; this threshold is primarily set by relative streaming motion between DM and baryons imprinted at recombination. We obtain similar results using subhalo MAHs from an extremely high-resolution cosmological DM--only zoom-in simulation of a Milky Way (MW) analog (particle mass $6.3\times 10^3{M}_{\odot }$). Based on the abundance of MW satellites, these results imply that at least some known ultra-faint dwarf galaxies formed through ${\mathrm{H}}_2$ cooling. This work sharpens predictions for the galaxy formation threshold and demonstrates how its essential features emerge from the underlying distribution of halo growth histories.

arXiv comment10 pages, 7 figures. Updated to published version

References in corpus (58)

• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• Statistical Properties of X-ray Clusters: Analytic and Numerical Comparisons
• How Do Galaxies Get Their Gas?
• The Rockstar Phase-Space Temporal Halo Finder and the Velocity Offsets of Cluster Cores
• The Formation of the First Star in the Universe
• Concentrations of Dark Halos from their Assembly Histories
• How small were the first cosmological objects?
• Multi-scale initial conditions for cosmological simulations
• Gravitationally Consistent Halo Catalogs and Merger Trees for Precision Cosmology
• The Birth of a Galaxy: Primordial Metal Enrichment and Stellar Populations
• Relative velocity of dark matter and baryonic fluids and the formation of the first structures
• Destruction of Molecular Hydrogen During Cosmological Reionization
• The Birth of a Galaxy - III. Propelling reionisation with the faintest galaxies
• Simulations of Pregalactic Structure Formation with Radiative Feedback
• Second-Generation Objects in the Universe: Radiative Cooling and Collapse of Halos with Virial Temperatures Above 10^4 Kelvin
• Formation of the First Stars
• Primordial Star Formation under the Influence of Far Ultraviolet Radiation: 1540 Cosmological Halos and the Stellar Mass Distribution
• The Photo-Evaporation of Dwarf Galaxies During Reionization
• Uncertainties in H2 and HD Chemistry and Cooling and their Role in Early Structure Formation
• An accurate physical model for halo concentrations
• The accretion history of dark matter halos III: A physical model for the concentration-mass relation
• The First Galaxies: Assembly, Cooling and the Onset of Turbulence
• A Cosmic UV/X-ray Background Model Update
• Population III star formation in a Lambda CDM universe, II: Effects of a photodissociating background
• Galaxy Formation and Reionization: Key Unknowns and Expected Breakthroughs by the James Webb Space Telescope
• Milky Way Satellite Census. II. Galaxy--Halo Connection Constraints Including the Impact of the Large Magellanic Cloud
• Be it therefore resolved: Cosmological Simulations of Dwarf Galaxies with Extreme Resolution
• Impact of the Relative Motion between the Dark Matter and Baryons on the First Stars
• Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1
• Suppression of H_2 Cooling in the Ultraviolet Background
• H_2 Cooling of Primordial Gas Triggered by UV Irradiation
• Connecting the first galaxies with ultra faint dwarfs in the Local Group: chemical signatures of Population~III stars
• The detailed structure and the onset of galaxy formation in low-mass gaseous dark matter haloes
• The Influence of Streaming Velocities on the Formation of the First Stars
• When did Population III star formation end?
• The influence of streaming velocities and Lyman-Werner radiation on the formation of the first stars
• Cradles of the first stars: self-shielding, halo masses, and multiplicity
• Quantifying scatter in galaxy formation at the lowest masses
• Legacy of star formation in the pre-reionization universe
• Going, going, gone dark: Quantifying the scatter in the faintest dwarf galaxies
• Coming of Age in the Dark Sector: How Dark Matter Haloes grow their Gravitational Potential Wells
• The critical dark matter halo mass for Population III star formation: dependence on Lyman-Werner radiation, baryon-dark matter streaming velocity, and redshift
• The Impact of HD Cooling on the Formation of the First Stars
• Symphony: Cosmological Zoom-in Simulation Suites over Four Decades of Host Halo Mass
• How low does it go? Too few Galactic satellites with standard reionization quenching
• GRUMPY: a simple framework for realistic forward-modelling of dwarf galaxies
• Starbursts in low-mass haloes at Cosmic Dawn. I. The critical halo mass for star formation
• Forecasts for Galaxy Formation and Dark Matter Constraints from Dwarf Galaxy Surveys
• A self-consistent semi-analytic model for Population III star formation in minihalos
• LYRA III: The smallest Reionization survivors
• Modelling the cosmological Lyman-Werner background radiation field in the Early Universe
• Milky Way-est: Cosmological Zoom-in Simulations with Large Magellanic Cloud and Gaia-Sausage-Enceladus Analogs
• A-SLOTH reveals the nature of the first stars
• Tracing stars in Milky Way satellites with A-SLOTH
• First estimate of the local value of the baryonic streaming velocity
• External Enrichment of Minihalos by the First Supernovae
• Fully Coupled Simulation of Cosmic Reionization. III. Stochastic Early Reionization by the Smallest Galaxies

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• Tiny galaxies and dark substructures: exploring the "dark" subhaloes in TNG50
• Born to be Starless: Revisiting the Missing Satellite Problem
• New insights on low-mass dark matter subhalo tidal tracks via numerical simulations
• DELVE Milky Way Satellite Galaxy Census I: Satellite Population and Survey Selection Function in DES, DELVE, and Pan-STARRS
• Impact of baryons on the population of Galactic subhalos and implications for dark matter searches
• Simulation based inference of the ionization history from the 2D 21 cm power spectrum
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