Ultra diffuse galaxies (UDGs) have the sizes of giant galaxies but the
luminosities of dwarfs. A key to understanding their origins comes from their
total masses, but their low surface brightnesses ($\mu(V) \geq$ 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 7 GCs we measure a mean systemic velocity $v_sys$
= 1071$^+14_-15$ km/s, thereby confirming a Virgo-cluster association. We
measure a velocity dispersion of 33$^+16_-10$ km/s within 8.1 kpc,
corresponding to an enclosed mass of $(4.5 2.8)\times10^9$ $M_ødot$
and a $g$-band mass-to-light ratio of $(M/L)_g = 106^+126_-54$. From the
cumulative mass curve, along with the GC numbers, we estimate a virial mass of
$\sim8\times10^10$ $M_ødot$, yielding a dark-to-stellar mass fraction of
$\sim3000$. We show that this UDG is an outlier in $M_star - M_\rm
halo$ 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.
Описание
[1602.04002] An overmassive Dark Halo around an Ultra-diffuse Galaxy in the Virgo Cluster
%0 Generic
%1 beasley2016overmassive
%A Beasley, Michael A.
%A Romanowsky, Aaron J.
%A Pota, Vincenzo
%A Navarro, Ignacio Martín
%A Delgado, David Martinez
%A Neyer, Fabian
%A Deich, Aaron L.
%D 2016
%K dark diffuse galaxies halos ultra
%T An overmassive Dark Halo around an Ultra-diffuse Galaxy in the Virgo
Cluster
%U http://arxiv.org/abs/1602.04002
%X Ultra diffuse galaxies (UDGs) have the sizes of giant galaxies but the
luminosities of dwarfs. A key to understanding their origins comes from their
total masses, but their low surface brightnesses ($\mu(V) \geq$ 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 7 GCs we measure a mean systemic velocity $v_sys$
= 1071$^+14_-15$ km/s, thereby confirming a Virgo-cluster association. We
measure a velocity dispersion of 33$^+16_-10$ km/s within 8.1 kpc,
corresponding to an enclosed mass of $(4.5 2.8)\times10^9$ $M_ødot$
and a $g$-band mass-to-light ratio of $(M/L)_g = 106^+126_-54$. From the
cumulative mass curve, along with the GC numbers, we estimate a virial mass of
$\sim8\times10^10$ $M_ødot$, yielding a dark-to-stellar mass fraction of
$\sim3000$. We show that this UDG is an outlier in $M_star - M_\rm
halo$ 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.
@misc{beasley2016overmassive,
abstract = {Ultra diffuse galaxies (UDGs) have the sizes of giant galaxies but the
luminosities of dwarfs. A key to understanding their origins comes from their
total masses, but their low surface brightnesses ($\mu(V) \geq$ 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 7 GCs we measure a mean systemic velocity $v_{\rm sys}$
= 1071$^{+14}_{-15}$ km/s, thereby confirming a Virgo-cluster association. We
measure a velocity dispersion of 33$^{+16}_{-10}$ km/s within 8.1 kpc,
corresponding to an enclosed mass of $(4.5 \pm 2.8)\times10^{9}$ $M_{\odot}$
and a $g$-band mass-to-light ratio of $(M/L)_g = 106^{+126}_{-54}$. From the
cumulative mass curve, along with the GC numbers, we estimate a virial mass of
$\sim8\times10^{10}$ $M_{\odot}$, yielding a dark-to-stellar mass fraction of
$\sim3000$. We show that this UDG is an outlier in $M_{\rm star} - M_{\rm
halo}$ 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.},
added-at = {2016-02-15T09:46:50.000+0100},
author = {Beasley, Michael A. and Romanowsky, Aaron J. and Pota, Vincenzo and Navarro, Ignacio Martín and Delgado, David Martinez and Neyer, Fabian and Deich, Aaron L.},
biburl = {https://www.bibsonomy.org/bibtex/20159ffc460ba9e563991a6980c0ec37c/miki},
description = {[1602.04002] An overmassive Dark Halo around an Ultra-diffuse Galaxy in the Virgo Cluster},
interhash = {f229d12444608e373da6f4f66ef04c82},
intrahash = {0159ffc460ba9e563991a6980c0ec37c},
keywords = {dark diffuse galaxies halos ultra},
note = {cite arxiv:1602.04002Comment: Accepted for publication in ApJ letters},
timestamp = {2016-02-15T09:46:50.000+0100},
title = {An overmassive Dark Halo around an Ultra-diffuse Galaxy in the Virgo
Cluster},
url = {http://arxiv.org/abs/1602.04002},
year = 2016
}