The central velocity dispersion of the Milky Way bulge
  Recent spectroscopic and photometric surveys are providing a comprehensive
view of the MW bulge stellar population properties with unprecedented accuracy.
This in turn allows us to explore the correlation between kinematics and
stellar density distribution, crucial to constraint the models of Galactic
bulge formation. GIBS revealed the presence of a velocity dispersion peak in
the central few degrees of the Galaxy by consistently measuring high velocity
dispersion in three central most fields. Due to suboptimal distribution of
these fields, all being at negative latitudes and close to each other, the
shape and extension of the sigma peak is poorly constrained. In this study we
address this by adding new observations distributed more uniformly and in
particular including fields at positive latitudes that were missing in
GIBS.MUSE observations were collected in four fields at
(l,b)=(0,+2),(0,-2),(+1,-1),(-1,+2). Individual stellar spectra were extracted
for a number of stars comprised between ~500 and ~1200, depending on the seeing
and the exposure time. Velocity measurements are done by cross-correlating
observed stellar spectra in the CaT region with a synthetic template, and
velocity errors obtained through Monte Carlo simulations, cross-correlating
synthetic spectra with a range of different metallicities and different noise
characteristics. We measure the central velocity dispersion peak within a
projected distance from the Galactic center of ~280pc, reaching sigma~140 km/s
at b=-1. This is in agreement with the results obtained previously by GIBS at
negative longitude. The central sigma peak is symmetric with respect to the
Galactic plane, with a longitude extension at least as narrow as predicted by
GIBS. As a result of the Monte Carlo simulations we present analytical
equations for the Rvel measurement error as a function of metallicity and SNR
for giant and dwarf stars.
