4–6 October 2023

Osservatorio Astrofisico di Torino, Turin, Italy

GaiaUnlimited Community Workshop 2

The Gaia selection function and how to use the GaiaUnlimited tools


The workshop's theme is the Gaia selection function and how to use it. This event will be a three-day workshop and unconference, where we will discuss and learn from each other about the finer details of the Gaia selection function and how to build and use it in various contexts. Participants will be working with the new GaiaUnlimited selection function tools, for which we will assist as needed, and we will improve them based on the feedback we'll receive. We hope this workshop could lead to some new collaborations or initial joint studies. We want to dedicate a significant amount of time to unconference sessions and informal discussions.

New in this workshop: Selection function tools for subsamples of the Gaia data and for combinations of Gaia with other photometric and spectroscopic surveys.

This workshop is part of the GaiaUnlimited project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004110.



The Gaia Unlimited Team

  • Adrian Price-Whelan (Flatiron)
  • Alfred Castro-Ginard (Leiden)
  • Andy Casey (Monash)
  • Anthony Brown (Leiden)
  • David Hogg (NYU/ Flatiron/ MPIA Heidelberg)
  • Hans-Walter Rix (MPIA Heidelberg)
  • Morgan Fouesneau (MPIA Heidelberg)
  • Ron Drimmel (INAF-Torino)
  • Shourya Khanna (INAF-Torino)
  • Tristan Cantat-Gaudin (MPIA Heidelberg)
  • Vasily Belokurov (IoA Cambridge)
  • Evgeny Kurbatov (IoA Cambridge)


The registration is closed.

Adrian Price-Whelan (Flatiron Institute)
Alessandro Mazzi (Università di Bologna)
Alessandro Spagna (INAF-OATo)
Alex Golovin (Landessternwarte, Heidelberg University)
Alex Wallace (Monash University)
Alfred Castro Ginard (Leiden Observatory)
Anthony Brown (Leiden Observatory)
David W Hogg (New York University)
Diego Osvaldo Ochoa de la Cruz (IA-UNAM)
Dmitry Chulkov (INASAN, Moscow, Russia)
Eleonora Zari (MPIA)
Eloisa Poggio (Observatoire de la Côte d'Azur)
Erasmo Trentin (Leibniz Institut für Astrophysik Potsdam (AIP))
Hai-Feng Wang (Rome University and Fermi Centre)
John Mora (Inter-University Centre for Astronomy and Astrophysics)
Madeline Lucey (University of Pennsylvania)
Marta González (Valencia International University)
Mauricio Cruz Reyes (EPFL)
Morgan Fouesneau (Max Planck Institute for Astronomy)
Nestor Arsenov (Bulgarian Academy of Sciences, Institute of Astronomy)
Oren Ironi (Weizmann Institute of Science)
Paola Re Fiorentin (INAF - Osservatorio Astrofisico di Torino)
Payel Das (University of Surrey)
Richard D'Souza (Vatican Observatory)
Richard Smart (OATo INAF)
Ronald Drimmel (INAF - Osservatorio Astrofisico di Torino)
Sara Gelsumini (University of Bologna)
Sebastian Ratzenböck (University of Vienna, Department of Astrophysics)
Shanika Galaudage (Observatoire de la Côte d'Azur)
Shourya Khanna (INAF Torino)
Sill Verberne (Leiden Observatory)
Taavet Kalda (Max Planck Institute for Astronomy)
Tristan Cantat-Gaudin (Max Planck Institute for Astronomy)
Zofia Kaczmarek (Max Planck Institute for Astronomy)



08:30 - 09:00 Participants' arrival
Registration, name tags, etc.
09:00 - 09:10 boot-up
Welcome and opening remarks
09:10 - 10:40 Pitch cards
Individual one-slide introductions slide deck
10:40 - 11:00 Coffee break
11:00 - 12:00 Session 1 - The Gaia selection function & GaiaUnlimited project
Gaia Unlimited Overview
An empirical calibration of the Gaia DR3 selection function
Selection Function for Gaia Subsamples
12:00 - 13:30 Lunch break
13:40 - 13:50 Daily Unconference Planning
Unconference topic selection and room allocation
14:00 - 15:50 Unconference and Tutorials
Walk-through of GaiaUnlimited tools
15:50 - 16:10 Coffee break
16:10 - 17:00 Unconference and Tutorials
How to use the selection function in practice
Example of Gaia+APOGEE
Example of Red Clump stars
17:00 - 17:15 Wrap-up
Reports on the unconference sessions. Sharing results and feedback.


09:00 - 09:10 boot-up
09:10 - 09:50 Session 2 - Selection functions of combined surveys
All-sky Red Clump Catalogue Galactic Structure & Selection Functions (Gaia + 2MASS example)
Combining Gaia and APOGEE
09:50 - 10:00 Daily unconference planning
Unconference topic selection and room allocation
10:00 - 10:30 Unconference and Tutorials
Working out a basic example and introduction to probabilistic graphical models
10:30 - 11:00 Coffee break
11:00 - 11:00 Unconference and Tutorials
Working out a basic example and introduction to probabilistic graphical models (continued)
11:30 - 12:00 Session 3 - Selection function for binary stars
Binary systems
12:00 - 13:30 Lunch break
13:30 - 14:10 Session 4 - Contributed talks
Gaia subpopulation completes estimation with machine learning
14:10 - 15:45 Unconference and Tutorials
15:45 - 16:15 Coffee break
16:15 - 17:00 Session 5 - Contributed talks
Discovering hypervelocity stars in surveys (and intro to simulating Gaia data)
17:00 - 17:15 Wrap-up
Reports on the unconference sessions. Sharing results and feedback.
20:00 - Dinner at Le Putrelle


09:00 - 09:10 boot-up
09:10 - 09:50 Session 6 - Contributed talks
Visual binary stars with known orbits in Gaia EDR3
Selection function for hot stars in the Milky Way disk
09:50 - 10:00 Daily unconference planning
Unconference topic selection and room allocation
10:00 - 10:30 Unconference and Tutorials
XP selection function
Accounting for FoV pointing in M10 maps
10:30 - 11:00 Coffee break
11:00 - 12:00 Unconference and Tutorials
Colour terms, i.e. the effects of dust
Selection function uncertainties
12:00 - 13:30 Lunch break
13:30 - 13:40 Final logistics
13:40 - 14:15 Unconference and Tutorials
14:15 - 15:00 G-U feedback and Gaia SF perspective
GaiaUnlimited: feedback and perspectives, by Anthony Brown
15:00 - Conference closed


The workshop will take place at the Istituto Nazionale di Ricerca Metrologica (INRiM) — Laboratorio Alte Tensioni e Forti Correnti.


The INRiM is close to the physics department of the University of Turin, on the edge of the Parco del Valentino on the Po River. It is within easy reach by public transport from the main train stations in Turin.

Don't hesitate to contact us if you need assistance or have questions.


Istituto Nazionale di Ricerca Metrologica

Corso Massimo D'Azeglio 42

Turin, Italy


The workshop will start at 09:00 on Wednesday, October 4 2022, and finish at 16:00 on Friday, October 6 2022.

Participants are responsible for organizing their travel to Turin and should make their own accommodation arrangements (see below).


There is no conference fee. All events happening at the venue are covered, but we cannot offer travel or lodging support.


If you need help with childcare arrangements, don't hesitate to contact us.

Lunches & Coffee Breaks


Workshop dinner

Thursday evening (day 2) of the workshop we will have a social dinner. The venue is Le Putrelle and they have prepared a menu that will cost 37€ per person, drinks included. Payment can be by card or cash, and a receipt will be provided for reimbursement purposes. If you are travelling with others, they are welcome, but we will need to know ahead of time. In order to let the restaurant know exactly how many we will be, we ask that you confirm your participation (or not) by filling out this Google form by September 22.

Dinner starts at 20:00


We are committed to providing an accessible environment for all participants. If you need help or arrangements, don't hesitate to contact the organizers.

Participants will pay attention not to leave out information for some people in your audience. Some of us might not be able to see well, hear well, move well, speak well, or understand information presented in some ways well or at all. Everyone at the event will be open to diversity in the audience and any accessibility issues. The Web Accessibility Initiative provides some information & directions.

Covid-19 measures

Please read the safety measures and guidelines for this workshop.


Participants are responsible for making their own accommodation arrangements.

The venue is pretty much in the city center. There is a large number of lodging options within 20-30 min of walking distance. We do not have specific recommendations, you can use your favorite search engine to find a place.

don't hesitate to contact us if you have any questions.


This workshop is an in-person event with the option for remote participation. In addition, we will use:



You may need to apply for a visa to enter Italy. See this overview of visa requirements.

Feel free to contact the organizers if you need a letter of support.

Getting to Turin

Driving directions

The center of Torino is restricted access (ZTL; Zona traffico limitato). Check with your hotel to make sure that they have available parking, and whether you need a temporary permit to reach them.


The two main train stations are Porta Nuova and Porta Susa. Assuming you are staying in a hotel near Piazza Vittorio, the most convenient public transport lines from Porta Susa are tram 13 or 13/ (dir Gran Madre), bus 55 (dir. Farini), or bus 56 (dir Tabacchi), while from Porta Nuova you will want to take bus 61 (dir San Mauro), but be aware that the bus stop for this line is not directly in front of the station, but on the east side of the station along Via Nizza. For the name of the bus/tram stop nearest your hotel, please check the hotel's website. Or you can easily get a taxi.


Transportation from the airport to Torino can be done by taxi or bus. There are two bus services available, Arriva and Flibco. One way tickets are less than 10€, and it may be convenient to buy a two way ticket for your return to the airport.

The first, Arriva, has blue and green buses with "Torino Airport" written on the side, and they depart every fifteen minutes, with an additional express line that runs once an hour (last run at 15:10) and goes directly to the Porta Susa train station. Tickets can be purchased at the information booth in the arrivals area, or directly on the bus with credit card or bancomat.

The second, Flibco, has bright green buses, and runs once every 30 minutes. Tickets may be purchased online, via their Flibco app, at a dedicated Flibco desk in the arrivals area, or on the bus.

For further information on bus services to and from the airport see this page.

Taxi rides to the center of Torino cost about 40€

There is a train station at the airport, but it is not convenient for reaching the city center.

Local public transport

If you arrive by train, or take the bus from the airport to bring you to Torino, you will arrive at the main train station, Porta Susa. Google Maps should work fine for finding public transport to your hotel, or you can get a taxi from there. For arriving at the venue, if walking is not an option, then bus number 12 stops in front of the meeting venue (stop "Politecnico"). You can buy bus tickets either at news kiosks or tabaccherie (tobacco shops indicated with a "T") or with a convenient app called "GTT - TO Move".

There are also bicycles and electric scooters scattered about that can be rented if you have data roaming on your phone.

Getting to the venue

See the "Venue" menu item.

Code of conduct

During the community workshop, we require participants to follow the code of conduct for the workshop which can be found below. If you have any questions about the workshop, you can reach the organizing committee.

The organizers are dedicated to providing a harassment-free conference experience for everyone, regardless of gender, gender identity and expression, age, sexual orientation, disability, physical appearance, body size, race, ethnicity, religion (or lack thereof), or technology choices. We do not tolerate harassment, abusive behavior, or intimidation of conference participants in any form. As such, we follow the European Astronomical Society Council (EAS) Ethics Statement and Guidelines for Good Practice and expect all participants to read and abide by their statements.

In addition to a general Code of Conduct and Ethics, all participants must agree with our collaboration policy: i.e., to openly share their ideas, expertise, code, and interim results. Project development will proceed out in the open among participants.

Participants are encouraged to change gears, start new collaborations, and drop or combine projects. Any participant contributing significantly to a project can expect appropriate credit vessels (e.g., co-authorship).

We pledge to help the entire community follow the code of conduct, and to not remain silent when we see violations of the code of conduct. We will take action when members of our community violate this code such as notifying a workshop organizer or talking privately with the person. This code of conduct applies to all community situations online and offline, including the conference itself, mailing lists, forums, social media, social events associates with the conference, and one-to-one interactions.

Participants asked to stop any harassing behavior are expected to comply immediately. Attendees violating these rules may be asked to leave the event at the sole discretion of the conference organizers.