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PreprintCC BY 4.0arXiv

Rubin Observatory Reveals a Dust-Shrouded Halo Globular Cluster in Ophiuchus

  • Aashay Pai
  • William Cerny
  • Andrew B. Pace
  • Alex Drlica-Wagner
  • Peter S. Ferguson
  • Marla Geha
  • Chin Yi Tan
  • Sasha N. Campana
  • Burçin Mutlu-Pakdil
  • Alexander H. Riley
  • Nora Shipp
  • Guy S. Stringfellow
Open at sourcePDFDOICite

Abstract

We present the discovery of the Milky Way satellite Rubin-GC1 (Rubin J1628-1735) using data from the NSF-DOE Vera C. Rubin Observatory's Early Data Preview 2. The system was discovered in the direction of the Galactic bulge with (l, b) ∼ (359∘, 21∘) in a region of high stellar density and a foreground reddening of E(B−V) ≈ 0.7. We simultaneously fit the morphology and isochrone parameters of Rubin-GC1, determining that it is a faint (MV = −2.4+0.5−0.7) and compact (r1/2 = 5+1−1 pc) Milky Way satellite at a distance of D⊙ = 31+3−3 kpc; its stellar population is intermediate-age (τ=9.2+1.2−0.7 Gyr) and moderately metal-rich ([Fe/H]iso=−0.73+0.04−0.04). Together, these properties suggest Rubin-GC1 is most likely a star cluster in the faint tail of the luminosity function of globular clusters surrounding the Milky Way. We identify a distinct proper motion signature from Rubin-GC1 in Gaia DR3, and from a comparison of the system's 5D phase space information to N-body models of the Sagittarius dwarf spheroidal galaxy's tidal stream, we determine that Rubin-GC1 is likely an accreted cluster associated with the Sagittarius leading arm. The discovery of Rubin-GC1 highlights the potential of Rubin to uncover faint, resolved satellites in dust-shrouded regions of the Milky Way, including remnants of the accretion events that have shaped the Galaxy's hierarchical assembly.

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Cite

BibTeXRIS
BibTeX
@misc{pai2026rubin,
  title = {{Rubin Observatory Reveals a Dust-Shrouded Halo Globular Cluster in Ophiuchus}},
  author = {Aashay Pai and William Cerny and Andrew B. Pace and Alex Drlica-Wagner and Peter S. Ferguson and Marla Geha and Chin Yi Tan and Sasha N. Campana and Burçin Mutlu-Pakdil and Alexander H. Riley and Nora Shipp and Guy S. Stringfellow},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.15872},
  eprint = {2609.15872},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.15872},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Rubin Observatory Reveals a Dust-Shrouded Halo Globular Cluster in Ophiuchus
AU  - Aashay Pai
AU  - William Cerny
AU  - Andrew B. Pace
AU  - Alex Drlica-Wagner
AU  - Peter S. Ferguson
AU  - Marla Geha
AU  - Chin Yi Tan
AU  - Sasha N. Campana
AU  - Burçin Mutlu-Pakdil
AU  - Alexander H. Riley
AU  - Nora Shipp
AU  - Guy S. Stringfellow
PY  - 2026
DA  - 2026/09/14
PB  - arXiv
DO  - 10.48550/arxiv.2609.15872
UR  - https://arxiv.org/abs/2609.15872
AB  - We present the discovery of the Milky Way satellite Rubin-GC1 (Rubin J1628-1735) using data from the NSF-DOE Vera C. Rubin Observatory's Early Data Preview 2. The system was discovered in the direction of the Galactic bulge with (l, b) ∼ (359^∘, 21^∘) in a region of high stellar density and a foreground reddening of E(B−V) ≈ 0.7. We simultaneously fit the morphology and isochrone parameters of Rubin-GC1, determining that it is a faint (M_V = −2.4^+0.5_−0.7) and compact (r_1/2 = 5^+1_−1 pc) Milky Way satellite at a distance of D_⊙ = 31^+3_−3 kpc; its stellar population is intermediate-age (τ=9.2^+1.2_−0.7 Gyr) and moderately metal-rich ([Fe/H]_iso=−0.73^+0.04_−0.04). Together, these properties suggest Rubin-GC1 is most likely a star cluster in the faint tail of the luminosity function of globular clusters surrounding the Milky Way. We identify a distinct proper motion signature from Rubin-GC1 in Gaia DR3, and from a comparison of the system's 5D phase space information to N-body models of the Sagittarius dwarf spheroidal galaxy's tidal stream, we determine that Rubin-GC1 is likely an accreted cluster associated with the Sagittarius leading arm. The discovery of Rubin-GC1 highlights the potential of Rubin to uncover faint, resolved satellites in dust-shrouded regions of the Milky Way, including remnants of the accretion events that have shaped the Galaxy's hierarchical assembly.
ER  -