Dark Star Clusters or Ultrafaint Dwarf Galaxies? Revisiting UMa3/U1

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

Dark Star Clusters or Ultrafaint Dwarf Galaxies? Revisiting UMa3/U1

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

Dark Star Clusters or Ultrafaint Dwarf Galaxies? Revisiting UMa3/U1

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10308 - Astronomy (including astrophysics,space science)

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Astrophysical Journal Letters

ISSN

2041-8205

e-ISSN

2041-8213

Svazek periodika

989

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

8

Strana od-do

L14

Kód UT WoS článku

001546484800001

EID výsledku v databázi Scopus

2-s2.0-105012750436