2026/05/31 by Ethan O. Nadler, Mustafa A. Amin, Risa H. Wechsler +4
Physics and Astronomy · #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph.CO #hep-ph
paper · pdf · doi:10.3847/2041-8213/ae8b9f
published as ApJL, 1006, 65 (2026) · 9 pages, 3 figures; updated to published version
arxiv created 2026/07/30 · openalex publication_date 2026/07/30 · arxiv updated 2026/07/31 · openalex created_date 2026/07/31 · openalex updated_date 2026/07/31
Abstract We generalize lower limits on the dark matter (DM) particle mass m derived from Milky Way (MW) satellite galaxy abundances to scenarios in which DM is an ultralight scalar field produced with a field power spectrum peaked at a subhorizon wavenumber k * . In these models, the DM field free-streams similarly to warm DM while also exhibiting significant small-scale wave interference effects. The resulting dimensionless density power spectrum shows two effects: (i) free-streaming suppression at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">fs</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">eq</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mo stretchy="false">[</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>a</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">eq</mml:mi> </mml:mrow> </mml:msub> <mml:mi>m</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mi>ln</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>a</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">eq</mml:mi> </mml:mrow> </mml:msub> <mml:mi>m</mml:mi> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo stretchy="false">]</mml:mo> </mml:math> ; and (ii) Poisson-like enhancement related to wave interference at k ≳ 10 −2 k * , which saturates near the Jeans scale k J ∼ k eq /( k * / a eq m ). Comparing these predictions with established constraints on a free-streaming cutoff in the linear matter power spectrum from the MW satellite population and assuming that warm ultralight DM does not change the form of the galaxy–halo connection relative to cold DM, we obtain m > 6 × 10 −18 eV ( k * /10 4 Mpc −1 ) for k * > 10 4 Mpc −1 at 95% confidence. For smaller k * , Poisson-noise enhancement on MW satellite scales weakens the constraint, yielding <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>m</mml:mi> <mml:mo>></mml:mo> <mml:mn>6</mml:mn> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>18</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">eV</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">Mpc</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> for k * < 10 4 Mpc −1 at 95% confidence.