S5 had its First Public Data Release on April 24, 2021. See the data section for more information.

About S5

Mapping stellar streams of the Milky Way with the Anglo-Australian Telescope

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 S5 Surveys

S5 pointing map


The main survey. The goal is to measure radial velocities and metallicities of stream members. S5 has mapped over 20 streams both inside and outside of DES footprint. We were the first spectroscopic observations of the DES streams.

Artist impression of The Milky Way


We use about a third of our 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.

(Credit: ESO/L. Calçada)
Low-z galaxy images


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.

(Credit: SDSS)
Artist impression of The Milky Way


We are also using Magellan/MIKE to obtain high-resolution spectra of bright stream members in order to derive stellar parameters and precise elemental abundances. These will enable us to understand the stream progenitors and chemical evolution.

(Credit: Jennifer Johnson • CC BY-SA-4.0)


Data Release 1

The First Public Data Release of the Southern Stellar Stream Spectroscopic Survey was on April 24, 2021. S5 DR1 contains data derived from all observations taken between 2018-2019. For details on target selection, data reduction, survey validation see Li et al. (2019) and see this PDF for documenation and column descriptions of S5 DR1.

DR1 can be downloaded from zenodo. There are two versions of the DR1: s5_pdr1.fits which contains all columns; and s5_pdr1_light.fits which only contains the small subset with the most frequently used columns.

If any data from this release is used for publication, please cite Li et al. (2019) for reference and include the following text in your acknowledgments:

Based on data acquired at the Anglo-Australian Telescope. We acknowledge the traditional owners of the land on which the AAT stands, the Gamilaraay people, and pay our respects to elders past and present.

Large data tables

We provide machine-readable versions of large tables published in our papers.

T. S. Li et al (2019) • The Overview paper

Ji et al (2020) • Chemical Abundances of Seven Stellar Streams

T. S. Li et al (2021) • Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream

There is a GitHub repository of data for this paper. This provides:

Reduced spectra

If you are interested in the S5 reduced spectra, please contact Ting Li.


  1. Shipp, N. et al (2019). Proper Motions of Stellar Streams Discovered in the Dark Energy Survey. The Astrophysical Journal (arXiv preprint)
  2. Li, T. S. et al (2019). The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science. Monthly Notices of the Royal Astronomical Society (arXiv preprint)
  3. Koposov, Sergey E. et al (2020). Discovery of a nearby 1700 km s-1 star ejected from the Milky Way by Sgr A*. Monthly Notices of the Royal Astronomical Society (arXiv preprint; Press coverage)
  4. Wan, Zhen et al (2020). The tidal remnant of an unusually metal-poor globular cluster. Nature (arXiv preprint; Press coverage)
  5. Ji, Alexander P. et al (2020). The Southern Stellar Stream Spectroscopic Survey (S5): Chemical Abundances of Seven Stellar Streams. The Astronomical Journal (arXiv preprint)
  6. Li, Ting S. et al (2021). Broken into Pieces: ATLAS and Aliqa Uma as One Single Stream. The Astrophysical Journal (arXiv preprint)
  7. Ji, Alexander P. et al (2021). Kinematics of Antlia 2 and Crater 2 from The Southern Stellar Stream Spectroscopic Survey (S5). In submission (arXiv preprint)
  8. Shipp, Nora et al (2021). Measuring the Mass of the Large Magellanic Cloud with Stellar Streams Observed by S5. In submission (arXiv preprint)
  9. Hansen, Terese T. et al (2021). S5: The Destruction of a Bright Dwarf Galaxy as Revealed by the Chemistry of the Indus Stellar Stream. The Astrophysical Journal (arXiv preprint)
  10. Casey, Andrew R. et al (2021). Signature of a massive rotating metal-poor star imprinted in the Phoenix stellar stream. In submission (arXiv preprint)

Press Coverage

S5 Membership

The S5 Collaboration consists of roughly 30 members spread across many institutions.

S5 is a collaboration between the members of the 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

S5 leadership team helps to coordinate the operational and scientific efforts of the collaboration.

Daniel Zucker

Daniel Zucker

Kyler Kuehn

Kyler Kuehn

Other team members

Denis Erkal

Denis Erkal

S5 Dynamical modeling coordinator

Alex Ji

Alex Ji

S5 HIRES coordinator

Sergey Koposov

Sergey Koposov

S5 Data release coordinator

Yao-Yuan Mao

Yao-Yuan Mao


Jeremy Mould

Jeremy Mould

Nora Shipp

Nora Shipp

S5 Proper motion coordinator

Jeffrey Simpson

Jeffrey Simpson

S5 Website coordinator


Sahar Allam, Eduardo Balbinot, Keith Bechtol, Vasily Belokurov, 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