Internal dynamics and stellar content of eight ultra-diffuse galaxies in the Coma cluster prove their evolutionary link with dwarf early-type galaxies. (arXiv:1901.05489v1 [astro-ph.GA])

Internal dynamics and stellar content of eight ultra-diffuse galaxies in the Coma cluster prove their evolutionary link with dwarf early-type galaxies. (arXiv:1901.05489v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chilingarian_I/0/1/0/all/0/1">Igor V. Chilingarian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Afanasiev_A/0/1/0/all/0/1">Anton V. Afanasiev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grishin_K/0/1/0/all/0/1">Kirill A. Grishin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fabricant_D/0/1/0/all/0/1">Daniel Fabricant</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moran_S/0/1/0/all/0/1">Sean Moran</a>

Ultra-diffuse galaxies (UDGs) are spatially extended low surface brightness
stellar systems with regular elliptical-like morphology. They are found in
large numbers in galaxy clusters and groups, but their formation and evolution
remain poorly understood because their low surface brightnesses have made
studies of their internal dynamics and dark matter content challenging. Here we
present spatially resolved velocity profiles, stellar velocity dispersions,
ages and metallicities of 8 UDGs in the Coma cluster. We use
intermediate-resolution spectra obtained with Binospec, the MMT’s new
high-throughput optical spectrograph. We derive dark matter fractions between
50% and 90% within the half-light radius using Jeans dynamical models. Two
galaxies exhibit major axis rotation, two others have highly anisotropic
stellar orbits, and one shows signs of triaxiality. In the Faber–Jackson and
mass–metallicity relations, the 8 UDGs fill the gap between cluster dwarf
elliptical (dE) and fainter dwarf spheroidal (dSph) galaxies. Overall, observed
properties of all 8 UDGs can be explained by a combination of internal
processes (supernovae feedback) and environmental effects (ram-pressure
stripping, interaction with neighbors). These observations suggest that UDGs
and dEs are members of the same galaxy population.

Ultra-diffuse galaxies (UDGs) are spatially extended low surface brightness
stellar systems with regular elliptical-like morphology. They are found in
large numbers in galaxy clusters and groups, but their formation and evolution
remain poorly understood because their low surface brightnesses have made
studies of their internal dynamics and dark matter content challenging. Here we
present spatially resolved velocity profiles, stellar velocity dispersions,
ages and metallicities of 8 UDGs in the Coma cluster. We use
intermediate-resolution spectra obtained with Binospec, the MMT’s new
high-throughput optical spectrograph. We derive dark matter fractions between
50% and 90% within the half-light radius using Jeans dynamical models. Two
galaxies exhibit major axis rotation, two others have highly anisotropic
stellar orbits, and one shows signs of triaxiality. In the Faber–Jackson and
mass–metallicity relations, the 8 UDGs fill the gap between cluster dwarf
elliptical (dE) and fainter dwarf spheroidal (dSph) galaxies. Overall, observed
properties of all 8 UDGs can be explained by a combination of internal
processes (supernovae feedback) and environmental effects (ram-pressure
stripping, interaction with neighbors). These observations suggest that UDGs
and dEs are members of the same galaxy population.

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