Dark Star Clusters or Ultrafaint Dwarf Galaxies? Revisiting UMa3/U1
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F25%3A10509920" target="_blank" >RIV/00216208:11320/25:10509920 - isvavai.cz</a>
Result on the web
<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=GY8sy.nLvu" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=GY8sy.nLvu</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.3847/2041-8213/adf320" target="_blank" >10.3847/2041-8213/adf320</a>
Alternative languages
Result language
angličtina
Original language name
Dark Star Clusters or Ultrafaint Dwarf Galaxies? Revisiting UMa3/U1
Original language description
Owing to sparse spectroscopic observations, the classification of faint satellites as either dark-matter-dominated dwarf galaxies or self-gravitating star clusters remains unresolved. The recently discovered Ursa Major III/UNIONS 1 (UMa3/U1) object, with its measured velocity dispersion, provides a rare observational anchor in this regime. Despite its cluster-like compactness, its inferred dynamical mass-to-light ratio (M-Dyn/L) suggests a dark-matter-dominated nature, prompting interpretations of UMa3/U1 as a microgalaxy, though current measurements remain inconclusive. Thousand-level M-Dyn/L values are not unique to galaxies; self-gravitating dark star clusters (DSCs) can reach comparable levels via energy injection driven by a centrally segregated black hole subsystem (BHSub), which accelerates the evaporation of luminous stars and leads to a supervirial appearance with elevated velocity dispersion. To assess whether UMa3/U1 is a DSC, we conducted direct N-body simulations and identified a model that successfully reproduces both its compact structure and elevated M-Dyn/L, supporting a self-gravitating cluster origin. We find the cluster entered the DSC phase around 4 Gyr ago, with its luminous stars expected to be depleted within the next 1 Gyr, followed by the gradual disruption of the central BHSub over the subsequent Gyr. We broaden our analysis by mapping DSC evolutionary tracks in the size versus total luminosity (L) and M-Dyn/L-L spaces, showing that DSCs occupy a region overlapping with faint, ambiguous satellites. In the M-Dyn/L-L diagram, DSCs trace a transitional channel bridging globular clusters and dwarf galaxies as they rise from M-Dyn/L approximate to 2 to 10(4) M-circle dot/L-circle dot.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10308 - Astronomy (including astrophysics,space science)
Result continuities
Project
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Continuities
I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace
Others
Publication year
2025
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Astrophysical Journal Letters
ISSN
2041-8205
e-ISSN
2041-8213
Volume of the periodical
989
Issue of the periodical within the volume
1
Country of publishing house
US - UNITED STATES
Number of pages
8
Pages from-to
L14
UT code for WoS article
001546484800001
EID of the result in the Scopus database
2-s2.0-105012750436