High Dispersion Measure Fast Radio Bursts from Young, Dust-Poor H II Regions

@misc{diggins2026high,
  title = {{High Dispersion Measure Fast Radio Bursts from Young, Dust-Poor H II Regions}},
  author = {Eliza C. Diggins and Calvin Leung and Wenbin Lu},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.27779},
  eprint = {2608.27779},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.27779},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - High Dispersion Measure Fast Radio Bursts from Young, Dust-Poor H II Regions
AU  - Eliza C. Diggins
AU  - Calvin Leung
AU  - Wenbin Lu
PY  - 2026
DA  - 2026/08/27
PB  - arXiv
DO  - 10.48550/arxiv.2608.27779
UR  - https://arxiv.org/abs/2608.27779
AB  - Several repeating fast radio burst (FRB) sources exhibit host-frame dispersion measure (DM) excesses far exceeding those expected from the interstellar medium in their host galaxies, implying a substantial contribution from the sub-kiloparsec-scale local environment. These excesses are often attributed to an expanding supernova remnant; however, this canonical interpretation does not explain their apparent preference for low-metallicity dwarf galaxy hosts, suggesting that the mechanism producing the local DM is coupled to the properties of the host galaxy. In this work, we investigate whether the H II regions generated by young, massive stellar associations can simultaneously explain these DM excesses and their preferential association with low-metallicity dwarf galaxies. We develop a semi-analytic model for FRB-emitting neutron stars in cluster-forming molecular clouds and perform idealized one-dimensional radiation-hydrodynamic simulations using time-dependent ionizing luminosities from pySTARBURST99. Our findings indicate that high-mass (M_⋆ ∼ 10^5−10^6 M_⊙), young (≲ 10 Myr) stellar associations in low-metallicity environments (LMC-like or lower) can produce DM_HII ≳ 10^3 pc cm^−3 for FRBs that form early (≲ 5 Myr) and remain embedded in the ionized gas. The low-mass/metallicity preference arises from dust: absorption of the Lyman continuum suppresses the ionized column at higher metallicity, making extreme local DMs preferentially generated in dust-poor, low-metallicity environments. At cosmological distances, selection of a metal-rich, massive, and quiescent host galaxy sample where such extreme local contributions are likely to be suppressed may yield a cleaner FRB sample for using extragalactic DMs as tracers of the intervening intergalactic and circumgalactic media.
ER  -