[Paper Review] Constraining Dark Matter models with extremely distant galaxies

M. Castellano, N. Menci+5 more|arXiv (Cornell University)|Mar 29, 2019

Dark Matter and Cosmic Phenomena4 citations

TL;DR

This paper uses the observed number density of ultra-faint, high-redshift galaxies from the Hubble Frontier Field to constrain alternative dark matter (DM) models. By comparing the predicted maximum halo number density in DM scenarios with the observed galaxy counts—under the conservative condition that galaxies cannot outnumber their host dark matter halos—it derives robust, baryonic-physics-independent limits on warm and fuzzy dark matter, strongly disfavoring fuzzy DM with masses below 10⁻²¹ eV and tightening constraints on keV-scale thermal and sterile neutrino DM candidates.

ABSTRACT

The investigation of distant galaxy formation and evolution is a powerful tool to constrain dark matter scenarios, supporting and in some cases surpassing other astrophysical and experimental probes. The recent completion of the Hubble Frontier Fields (HFF) programme combining ultra-deep Hubble Space Telescope observations and the magnification power of gravitational lensing produced by foreground galaxy clusters has enabled the detection of the faintest primordial galaxies ever studied. Here we show how the number density of such primordial galaxies allows to constrain a variety of DM models alternative to CDM. In particular, it provides stringent limits on the mass of thermal WDM candidates, on the parameter space of sterile neutrino production models, and on other DM scenarios featuring particles in the keV mass range which is also supported by recent detections of a 3.5keV X-ray line. These constraints are robust and independent of the baryonic physics modeling of galaxy formation and evolution. Fuzzy DM (ultralight DM particles) results strongly disfavored.

Motivation & Objective

• To provide robust, baryonic-physics-independent constraints on alternative dark matter models using the number density of high-redshift galaxies.
• To test whether the observed abundance of faint, lensed galaxies at z ≈ 6 can rule out or limit non-Cold Dark Matter scenarios.
• To evaluate the viability of keV-scale thermal WDM, sterile neutrinos, and ultralight fuzzy DM in light of recent HFF observations.
• To improve upon existing astrophysical bounds by leveraging the extreme sensitivity of the Hubble Frontier Field to faint, high-redshift sources.

Proposed method

• Uses the Hubble Frontier Field (HFF) survey to measure the UV luminosity function (LF) of ultra-faint, lensed galaxies down to M_UV = -12.5 at z ≈ 6.
• Applies the condition that the observed galaxy number density (φ_obs) cannot exceed the maximum predicted number density of dark matter halos (φ̄) to constrain DM models.
• Computes the halo mass function (dφ/dlogM) for various DM models using the extended Press-Schechter formalism and power spectrum suppression due to free streaming.
• For WDM, derives constraints based on the thermal relic mass m_X by comparing φ̄(m_X) to φ_obs, assuming free-streaming suppresses small-scale structure.
• For sterile neutrinos, evaluates both resonant (RP) and decay (SD) production mechanisms, constraining mixing angles and Yukawa couplings via the φ̄ ≥ φ_obs condition.
• For fuzzy DM, computes the cumulative halo mass function for varying particle masses (m_ψ) and derives lower bounds on m_ψ from the observed galaxy density.

Experimental results

Research questions

• RQ1 What constraints can be placed on the mass of thermal warm dark matter (WDM) particles using the number density of high-redshift galaxies?
• RQ2 How do the observed galaxy counts in the Hubble Frontier Field constrain sterile neutrino production models with keV-scale masses?
• RQ3 To what extent does the observed abundance of faint high-redshift galaxies disfavor ultralight fuzzy dark matter (FDM) with masses around 10⁻²² eV?
• RQ4 How do these constraints compare to those derived from Lyman-α forest data or X-ray line detections, and what advantages does the HFF method offer?
• RQ5 How robust are these constraints to uncertainties in lensing magnification and source redshift estimation in the HFF data?

Key findings

• The thermal WDM particle mass is constrained to m_X ≥ 2.9 keV at 1σ and m_X ≥ 2.4 keV at 2σ confidence level, based on the observed galaxy number density.
• For sterile neutrinos with a mass of 7.1 keV that could explain the 3.5 keV X-ray line, the resonant production mixing angle is constrained to -11.4 ≤ log(sin²(2θ)) ≤ -10.2 at 1σ.
• The Yukawa coupling y for sterile neutrino production via decay (SD model) is constrained to y ≥ 9×10⁻⁹ at 2σ confidence level.
• Fuzzy dark matter with particle mass m_ψ < 10⁻²¹ eV is strongly disfavored, with a lower limit of m_ψ ≥ 10⁻²¹ eV at 3σ confidence level.
• The constraints are robust and independent of baryonic physics modeling, offering a conservative and complementary probe to hydrodynamical simulations and X-ray observations.
• Future improvements from JWST, with deeper imaging and larger samples reaching M_UV ≈ -11, are expected to significantly tighten these constraints.