Constraining Baryonic Feedback at z∼ 1 with the Hα Luminosity Function

@misc{rapoport2026constraining,
  title = {{Constraining Baryonic Feedback at $z\sim 1$ with the H$α$ Luminosity Function}},
  author = {Ivan Rapoport and Vincent Desjacques and Ehud Behar and Shmuel Bialy},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.30698},
  eprint = {2608.30698},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.30698},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Constraining Baryonic Feedback at z∼ 1 with the Hα Luminosity Function
AU  - Ivan Rapoport
AU  - Vincent Desjacques
AU  - Ehud Behar
AU  - Shmuel Bialy
PY  - 2026
DA  - 2026/08/31
PB  - arXiv
DO  - 10.48550/arxiv.2608.30698
UR  - https://arxiv.org/abs/2608.30698
AB  - Baryonic feedback remains one of the primary uncertainties in galaxy formation models because of its impact on the interstellar medium (ISM) and star formation. We investigate its effect on the Hα luminosity function (LF) using the Illustris and IllustrisTNG simulations, incorporating direction-dependent dust attenuation and a physically motivated treatment of the propagation of Lyman-series photons. We model three sources of Hα emission: star-forming H II regions, collisional excitation and recombination in the diffuse ISM, and AGN-induced photo-excitation of diffuse gas. The models are calibrated against observed Hα LFs at z∼ 1−1.5 using a single free parameter relating the star formation rate to the H II-region Hα luminosity. We find that emission from diffuse gas contributes ∼ 1%−10% of the total Hα luminosity in both simulation sets. AGN photo-excitation produces only a modest enhancement of the bright end of the LF, although it dominates the Hα emission of Illustris galaxies with L_Hα≳ 3×10^42 erg s^−1. The low-feedback IllustrisTNG simulations provide good agreement with the observed LFs for all emission models considered, whereas the high-feedback Illustris simulation fails to simultaneously reproduce the faint and bright ends of the LF at z∼ 1. This tension between Hα LFs and stacked kSZ measurements highlights the combined power of these probes for constraining the interplay between baryonic feedback, gas properties, and the physics governing emission-line galaxies.
ER  -