The Dawning of the Stream of Aquarius in RAVE
ArXiv 1012.2127 (2010)
Authors:
Mary EK Williams, Matthias Steinmetz, Sanjib Sharma, Joss Bland-Hawthorn, Roelof S de Jong, George M Seabroke, Amina Helmi, Kenneth C Freeman, James Binney, Ivan Minchev, Olivier Bienaymé, Rachel Campbell, Jon P Fulbright, Brad K Gibson, Gerard F Gilmore, Eva K Grebel, Ulisse Munari, Julio F Navarro, Quentin A Parker, Warren Reid, Arnaud Siebert, Alessandro Siviero, Fred G Watson, Rosemary FG Wyse, Tomaz Zwitter
Abstract:
We identify a new, nearby (0.5 < d < 10 kpc) stream in data from the RAdial
Velocity Experiment (RAVE). As the majority of stars in the stream lie in the
constellation of Aquarius we name it the Aquarius Stream. We identify 15
members of the stream lying between 30 < l < 75 and -70< b <-50, with
heliocentric line-of-sight velocities V_los~-200 km/s. The members are outliers
in the radial velocity distribution, and the overdensity is statistically
significant when compared to mock samples created with both the Besan\c{c}on
Galaxy model and newly-developed code Galaxia. The metallicity distribution
function and isochrone fit in the log g - T_eff plane suggest the stream
consists of a 10 Gyr old population with [m/H]~-1.0. We explore relations to
other streams and substructures, finding the stream cannot be identified with
known structures: it is a new, nearby substructure in the Galaxy's halo. Using
a simple dynamical model of a dissolving satellite galaxy we account for the
localization of the stream. We find that the stream is dynamically young and
therefore likely the debris of a recently disrupted dwarf galaxy or globular
cluster. The Aquarius stream is thus a specimen of ongoing hierarchical Galaxy
formation, rare for being right in the solar suburb.
