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PreprintCC BY 4.0arXiv

Prospects for Near-Far Constraints on Reionization from Simulated LSST Observations of Milky Way Dwarf Galaxies and Stellar Streams

  • Aritra Kundu
  • Robyn Sanderson
  • Nora Shipp
  • Adrien Thob
  • Adam Lidz
  • Nondh Panithanpaisal
Open at sourcePDFDOICite

Abstract

The NSF-DOE Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will detect resolved stellar populations of intact dwarf galaxies and disrupted stellar streams in the Milky Way (MW) halo and beyond, opening a new avenue for near-field cosmology, particularly for constraining the faint galaxies during reionization. To interpret these data, we present and publicly release mock LSST catalogs of satellites, stellar streams, phase-mixed galaxies, and field galaxies around 13 MW-mass hosts in the FIRE-2 zoom-in simulations, generated with \textsf{py-ananke}. Using a surface brightness limit of μg ≤ 34 mag arcsec−2, we find that ≈29% of streams with M⋆ ≳ 5 × 105 M⊙ are detectable with tidal tails, while another ≈38% are detectable only through their bound progenitors and would appear as satellites. We estimate that ≈96% of satellites and ≈64% of field galaxies (out to ∼3.5 Mpc) with M⋆ ≳ 105 M⊙ are detectable, decreasing to ≈59\% and ≈42\% for M⋆ ≳ 104.5 M⊙ owing to resolution limits. Including streams detectable as satellites reproduces the radial distribution of observed MW satellites, suggesting that some observed satellites may be bound remnants of disrupted systems. Our mock galaxies match the sizes of observed satellites with MV ≲ −6. Star-formation histories computed from only the detectable stars broadly recover the simulated star-formation histories. As an application, we test the near-far technique for reconstructing the proto-MW ultraviolet luminosity function (UVLF) during reionization (z ≳ 6). Adding the detectable streams improves the recovered faint-end slope at z = 7 and reduces the halo-to-halo scatter by ≈33%.

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Cite

BibTeXRIS
BibTeX
@misc{kundu2026prospects,
  title = {{Prospects for Near-Far Constraints on Reionization from Simulated LSST Observations of Milky Way Dwarf Galaxies and Stellar Streams}},
  author = {Aritra Kundu and Robyn Sanderson and Nora Shipp and Adrien Thob and Adam Lidz and Nondh Panithanpaisal},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.36056},
  eprint = {2610.36056},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.36056},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Prospects for Near-Far Constraints on Reionization from Simulated LSST Observations of Milky Way Dwarf Galaxies and Stellar Streams
AU  - Aritra Kundu
AU  - Robyn Sanderson
AU  - Nora Shipp
AU  - Adrien Thob
AU  - Adam Lidz
AU  - Nondh Panithanpaisal
PY  - 2026
DA  - 2026/10/26
PB  - arXiv
DO  - 10.48550/arxiv.2610.36056
UR  - https://arxiv.org/abs/2610.36056
AB  - The NSF-DOE Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will detect resolved stellar populations of intact dwarf galaxies and disrupted stellar streams in the Milky Way (MW) halo and beyond, opening a new avenue for near-field cosmology, particularly for constraining the faint galaxies during reionization. To interpret these data, we present and publicly release mock LSST catalogs of satellites, stellar streams, phase-mixed galaxies, and field galaxies around 13 MW-mass hosts in the FIRE-2 zoom-in simulations, generated with \textsf{py-ananke}. Using a surface brightness limit of μ_g ≤ 34 mag arcsec^−2, we find that ≈29% of streams with M_⋆ ≳ 5 × 10^5 M_⊙ are detectable with tidal tails, while another ≈38% are detectable only through their bound progenitors and would appear as satellites. We estimate that ≈96% of satellites and ≈64% of field galaxies (out to ∼3.5 Mpc) with M_⋆ ≳ 10^5 M_⊙ are detectable, decreasing to ≈59\% and ≈42\% for M_⋆ ≳ 10^4.5 M_⊙ owing to resolution limits. Including streams detectable as satellites reproduces the radial distribution of observed MW satellites, suggesting that some observed satellites may be bound remnants of disrupted systems. Our mock galaxies match the sizes of observed satellites with M_V ≲ −6. Star-formation histories computed from only the detectable stars broadly recover the simulated star-formation histories. As an application, we test the near-far technique for reconstructing the proto-MW ultraviolet luminosity function (UVLF) during reionization (z ≳ 6). Adding the detectable streams improves the recovered faint-end slope at z = 7 and reduces the halo-to-halo scatter by ≈33%.
ER  -