S5 is a spectroscopic survey that began in 2018 using the 2dF/AAOmega spectrograph on the 3.9-metre Anglo-Australian Telescope at Siding Spring Observatory. The aim is to map the kinematics and chemistry of stellar streams in the Southern Hemisphere. The initial focus has been on recently identified streams within the footprint of the Dark Energy Survey (DES), with the eventual goal of surveying the entire southern sky.
The streams represent material tidally striped from dwarf galaxies and globular clusters and hence are essential dynamical probes of the dark matter distribution of the Milky Way, as well as providing a detailed snapshot of its accretion history.
The 350 science fibres of the 2dF fibre positioner, the precise photometry of DES DR1, and the superb proper motions from Gaia DR2 allow us to conduct an efficient spectroscopic survey to map these DES streams. In addition to the stream survey, we use spare fibres on each pointing to undertake a Milky Way halo survey, and a low-redshift galaxy survey.
The main survey. The goal is to measure radial velocities and metallicities of stream members. So far S5 has mapped 9 DES streams and 3 streams outside of DES; the former are the first spectroscopic observations of these recently discovered streams.
We are able to use some spare fibres for a Milky Way halo survey. This has the aim of observing interesting objects in the halo such as hyper-velocity stars, extremely metal-poor stars, RR Lyraes, and white dwarfs.
Nearby faint galaxies are difficult to distinguish from the far more numerous background galaxy population via photometry alone. The goal of including low-redshift (low-z) galaxy targets in S5 is to increase the number of spectroscopically confirmed low-z galaxies in order to better train photometric selection algorithms, and help build a statistic sample of very low-z galaxies.
We are using Magellan/MIKE to follow up bright stream members in order to derive detail elemental abundances. These will enable us to understand the stream progenitors and chemical evolution.
S5 is a collaboration between the members DES Milky Way Working Group and a group of Australian astronomers.
If you are interested in getting involved in S5, please contact Ting Li or other members in the S5 leadership team.
S5 leadership team helps to coordinate the operational and scientific efforts of the collaboration.
S5 Dynamical modeling coordinator
S5 High-resolution coordinator
S5 Data release coordinator
S5 Proper motion coordinator
S5 Website coordinator
Sahar Allam, Eduardo Balbinot, Keith Bechtol, Vasily Belokurov, Joss Bland-Hawthorn, Andrew Casey, Lara Cullinane, Gary Da Costa, Gayandhi De Silva, Alex Drlica-Wagner, Marla Geha, Dougal Mackey, Sarah Martell, Andrew Pace, Sanjib Sharma, Josh Simon, Douglas Tucker, Kathy Vivas, Zhen Wan, Risa Wechsler, Brian Yanny