Bibcode
Beasley, M. A.; Romanowsky, Aaron J.; Pota, Vincenzo; Martin Navarro, I.; Martinez Delgado, David; Neyer, Fabian; Deich, Aaron L.
Referencia bibliográfica
The Astrophysical Journal Letters, Volume 819, Issue 2, article id. L20, 7 pp. (2016).
Advertised on:
3
2016
Número de citas
156
Número de citas referidas
147
Descripción
Ultra-diffuse galaxies (UDGs) have the sizes of giants but the
luminosities of dwarfs. A key to understanding their origins comes from
their total masses, but their low surface brightnesses (μ (V)
≥slant 25.0) generally prohibit dynamical studies. Here, we report
the first such measurements for a UDG (VCC 1287 in the Virgo cluster),
based on its globular cluster system dynamics and size. From seven GCs
we measure a mean systemic velocity vsys =
{1071}-15+14 km s‑1, thereby
confirming a Virgo cluster association. We measure a velocity dispersion
of {33}-10+16 km s‑1 within 8.1
kpc, corresponding to an enclosed mass of (4.5 ± 2.8) ×
109M⊙ and a g-band mass-to-light ratio of
{({\text{}}M/L)}g={106}-54+126 within
an effective radius. From the cumulative mass curve, along with the GC
numbers, we estimate a virial mass of ∼8 ×
1010M⊙, yielding a dark-to-stellar mass
fraction of ∼3000. We show that this UDG is an outlier in
Mstar–Mhalo relations, suggesting extreme
stochasticity in relatively massive star-forming halos in clusters.
Finally, we discuss how counting GCs offers an efficient route to
determining virial masses for UDGs.