The Hidden Baryonic Sector: Compact Remnants, Fractal Cold Gas, and the Non-Vacuum Dark Mass Budget

Papers #14 and #15 (combined) of the research programme "What If the Vacuum Gravitates Locally?" The vacuum capture model (Paper #12) identifies quantum vacuum energy as the dominant dark component inside galaxies (~80–90%), but finds a systematic 10–20% residual at intermediate radii (10–30 kpc) that must be baryonic. This paper quantifies that residual. Part A constructs a census of the Milky Way's compact stellar remnants — white dwarfs, neutron stars, stellar-mass black holes, brown dwarfs, and intermediate-mass black holes from direct collapse at z > 6 — by integrating the star-formation history over 13 Gyr with a metallicity-dependent initial mass function (fiducial high-mass slope α₃ = −1.5 at Z < 10⁻⁴ Z☉). Total remnant mass: M_rem ≈ (3.1 ± 1.5) × 10¹⁰ M☉, dominated (~60%) by black holes from metal-poor progenitors. Part B develops a fractal model for molecular hydrogen at T ≲ 10 K in the galactic halo, organized in self-similar cloudlets with filling factor f ~ 10⁻³ and fractal dimension D ≈ 2.3. Total cold-gas mass: M_gas ≈ (1.5 ± 0.8) × 10¹⁰ M☉. The combined baryonic dark sector, M_rem + M_gas ≈ (4.6 ± 1.7) × 10¹⁰ M☉, is consistent with the vacuum-model residual across the full range of σ_v allowed by rotation-curve measurements. A sensitivity analysis shows the required residual varies from ~2 × 10¹⁰ M☉ (at σ_v = 170 km/s) to ~9 × 10¹⁰ M☉ (at σ_v = 150 km/s), bracketing the available baryonic budget. Detectability predictions are provided for ngVLA (molecular absorption at ~3 K), SKA (HI 21-cm absorption, FRB dispersion variance), LISA (intermediate-mass black hole mergers at ~10⁻⁵ yr⁻¹ per galaxy), and Roman (microlensing toward M31). IMBH merger predictions are compared against current LIGO/Virgo O4 upper limits. No new particles, no new forces, no free parameters beyond the QCD-derived coupling α = 0.005. Recommended for submission to The Astrophysical Journal. Keywords: dark matter, baryonic mass, compact remnants, direct collapse black holes, cold molecular gas, fractal ISM, galactic halos, rotation curves, initial mass function, vacuum energy, missing mass, quantum vacuum, cosmology Related identifiers: Paper #12: The Vacuum Capture Model (doi:10.5281/zenodo.19020123) — establishes the vacuum baseline and the 15–20% residual quantified here Paper #3a: The Vacuum–Matter Coupling from Finite-Density QCD (doi:10.5281/zenodo.19017167) Paper #9: N-body Simulations with a Gravitating Vacuum Phase (doi:10.5281/zenodo.19014206) License: Creative Commons Attribution 4.0 International (CC BY 4.0) Resource type: Preprint Communities: Astronomy, Astrophysics, Cosmology Authors: Boris Kriger Institute of Integrative and Interdisciplinary Research, Department of Cosmology and Theoretical Physics ORCID: 0009-0001-0034-2903