STScI's 2020 Virtual Symposium - THE LOCAL GROUP: Assembly & Evolution

A. Calamida (calamida[at], E. Sacchi (esacchi[at], S. T. Sohn (tsohn[at]

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Our 2020 STScI Symposium, "The Local Group: Assembly and Evolution," was held on August 31–September 4, 2020. This was the first time an STScI conference was organized in a fully virtual format. The symposium had about 160 registered participants from 22 different countries. BlueJeans Events was used as the talk platform and Slack was used for most of the interactions including questions and answers, topical discussions, and poster sessions.

The symposium brought together the stellar populations and the galaxy evolution communities to address some of the most outstanding questions in the field, such as:

  1. How did the Milky Way system assemble and form?
  2. How similar/different are the Milky Way and M31 systems?
  3. What mechanisms drive the formation and evolution of the Local Group and its constituent galaxies?
  4. What can we learn about the Local Group by studying other groups and clusters in the local Universe?

The abstract selection process was completely anonymous, to avoid any potential biases the reviewers might have had. The submissions were processed through a Google form and fed to a Python pipeline that assigned material to the SOC for review. Details of the process and the results are discussed in the related Newsletter article. We believe our methodology resulted in a balanced and diverse program. This outstanding achievement resulted in our recommending similar anonymized abstract selection processes to be used in future conferences.

Originally, the on-site Symposium was scheduled for three days of about eight hours each; however, considering the virtual environment, the SOC decided to spread out the meeting to five days of about five hours each day. A total of 159 participants virtually attended the Symposium through our BlueJeans Event platform, but up to 226 people connected to the conference. There were a total of 68 talks: 7 invited (30 minutes each including questions), 39 regular (15 minutes each), and 22 short talks (5 minutes each). The talks were presented via Bluejeans Events, while questions and answers were communicated in a separate Slack channel for each talk session. There were 42 posters presented during the Symposium. Each poster had its dedicated Slack channel, where participants actively joined and chatted with the presenter. The last hour of each day (Monday–Thursday) was dedicated to a poster session. The Slack platform was also used to foster discussion among the participants through different channels, such as the "virtual cafeteria," or through small group calls. This method of combining two different platforms to support talks, posters, questions and discussions worked extremely well and most of the participants were satisfied according to our symposium exit survey (see below). A general Slack channel was available for participants to contact the SOC, and a private SOC channel helped greatly in coordinating and managing the meeting. These separate channels allowed participants to be free from using the BlueJeans chat so as not to compete with the presentations on the same platform.

The first couple of days were dedicated to the Milky Way and its assembly and formation history, and included two invited talks, one on the Galactic bulge and its globular clusters, and one on stellar streams in the halo. The other talks in this session presented a range of different results based on the chemistry, kinematics, and spatial distribution of stars in the Galaxy and models. It was shown that the Milky Way underwent different merger and interaction events with other satellite galaxies, which shaped the disk, bulge, and halo structure. Several presentations focused on stellar streams and how to use them as tools for understanding properties of the Milky Way's dark-matter halo. Dwarf galaxies, as well as individual halo stars were demonstrated to be useful as tracer objects of the Galactic potential. Other talks highlighted various properties of dwarf galaxies, including chemical compositions and how they help improve our understanding of the assembly of the Milky Way. These discoveries were possible thanks to not only the improvement of models, but also the availability of accurate photometric, spectroscopy, and kinematical measurements from surveys such as Gaia, APOGEE, SDSS, DES, and Skymapper.

Across two sessions, particular focus was put on the Magellanic System. There was a huge amount of exciting data on the Large and Small Magellanic Clouds, pointing out how this is probably the closest example of a merging in action, which can give us a fundamental counterpart to compare to theory and simulations. Moreover, we are seeing more and more how the LMC is massive enough and on an orbit such that it is inducing a significant disturbance in the Milky Way, which we can see signatures of in the stellar and dark-matter halos.

The M31 system was the main topic of the following session. M31 underwent a more violent, albeit qualitatively similar, level of merging history compared to the Milky Way. Some presentations focused on the origins of the planes of satellites found around both the Milky Way and M31, and compared these two systems.

One of our goals was to put our Local Group into a broader context to understand how typical it is, and find out what we are able to learn about it by studying other groups and clusters in the local Universe. For this reason, we also hosted several talks about future facilities and surveys, which will provide new high-quality data and unlock key details on these science topics.

Near the end of the Symposium, we asked the participants to fill out an exit survey and received 93 responses. The majority of participants reported that the video/audio connections were satisfactory, and that the 5‑hour daily schedule had worked fine. Noteworthily, the participants were mostly happy about using Slack as the platform for active discussion and posters.

The chairs would like to thank all the members of the SOC, the EPG and IT groups at STScI, and all the amazing people that helped us make this symposium a big success!