Deep in the Fields of the Andromeda Halo: Discovery of the Pegasus VII Dwarf Galaxy in UNIONS
Abstract We present the newly discovered dwarf galaxy Pegasus VII (Peg VII), a member of the M31 subgroup which has been uncovered in the ri photometric catalogs from the Ultraviolet Near-Infrared Optical Northern Survey and confirmed with follow-up imaging from both the Canada–France–Hawaii Telescope and the Gemini-North Telescope. This system has an absolute V -band magnitude of −5.7 ± 0.2 mag and a physical half-light radius of 177 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>34</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>36</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> pc, which is characteristic of dynamically confirmed Milky Way satellite dwarf galaxies and about 5 times more extended than the most extended M31 globular clusters. Peg VII lies at a three-dimensional separation from M31 of 331 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> kpc, and a significant elongation ( ϵ ∼ 0.5) toward the projected direction of M31 could be indicative of a past tidal interaction, but additional investigation into the orbit, star formation history, and whether any gas remains in the galaxy is needed to better understand the evolution of Peg VII.
Authors
- E. A. Magnier (ORCID: https://orcid.org/0000-0002-7965-2815)
- Julio F. Navarro (ORCID: https://orcid.org/0000-0003-3862-5076)
- Michael J. Hudson (ORCID: https://orcid.org/0000-0002-1437-3786)
- Stephen Gwyn (ORCID: https://orcid.org/0000-0001-8221-8406)
- Alan W. McConnachie (ORCID: https://orcid.org/0000-0003-4666-6564)
- M. Gatto (ORCID: https://orcid.org/0000-0003-4636-6457)
- Simon E. T. Smith (ORCID: https://orcid.org/0000-0002-6946-8280)
- Christian R. Hayes (ORCID: https://orcid.org/0000-0003-2969-2445)
- K. C. Chambers
- Jean‐Charles Cuillandre (ORCID: https://orcid.org/0000-0002-3263-8645)
- Nicolas F. Martin (ORCID: https://orcid.org/0000-0002-1349-202X)
Institutions
- Herzberg Institute of Astrophysics (CA)
- Centre National de la Recherche Scientifique (FR)
- Space Telescope Science Institute (US)
- University of Hawaii System (US)
- University of Waterloo (CA)
- Perimeter Institute (CA)
- University of Victoria (CA)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- Université Paris-Saclay (FR)
- Astronomical Observatory of Capodimonte (IT)
- Observatoire astronomique de Strasbourg (FR)
- Astrophysique, Instrumentation et Modélisation (FR)
- Max Planck Institute for Astronomy (DE)
- Université Bourgogne Franche-Comté (FR)
- CEA Paris-Saclay (FR)
- Université de Strasbourg (FR)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-04-04
- DOI
- https://doi.org/10.3847/1538-4357/adb4f3
- Citations
- 3
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 2.31
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- Nuclear Safety and Security Commission
- Korea Astronomy and Space Science Institute
- Centre National de la Recherche Scientifique
- National Astronomical Observatory of Japan
- Ministério da Ciência, Tecnologia, Inovações e Comunicações
- Agencia Nacional de Investigación y Desarrollo
- Canadian Space Agency