Substellar Science with the Euclid Space Mission

Project Information

SUBSTELLAR

Grant agreement ID: 101054354

DOI

10.3030/101054354

EC signature date 30 September 2022

Start date 1 January 2023

End date 31 December 2027

Funded under

• European Research Council (ERC)

Total cost

€ 2 495 625,00

EU contribution

€ 2 495 625,00

Coordinated by

INSTITUTO DE ASTROFISICA DE CANARIAS
Spain

Periodic Reporting for period 1 - SUBSTELLAR (Substellar Science with the Euclid Space Mission)

Reporting period: 2023-01-01 to 2025-06-30

Summary of the context and overall objectives of the project

SUBSTELLAR is an Advanced Grant awarded to Prof. Eduardo L. Martín (Instituto de Astrofísica de Canarias) by the European Research Council.

Substellar Science with the Euclid Space Mission (SUBSTELLAR) is a project aimed at mining the Euclid surveys for pushing the frontier of knowledge in substellar science.

The primary science goal of SUBSTELLAR is to reveal and investigate the faint objects that lurk in the darkness beyond the limits of stellar engines, using mainly the new data arriving from the ESA Euclid space mission.

Euclid is a space mission led by the European Space Agency (ESA) to conduct a deep, single-epoch survey of 15,000 deg2 of sky with visible and near-infrared photometry and spectroscopy, and 40 deg2 multi-epoch very deep surveys. Euclid was launched at July 1st 2023. The unprecedented combination of sensitivity, areal coverage, spatial resolution, data homogeneity and spectral information will naturally be of tremendous benefit to other areas of astrophysics.

Two Euclid Independent Legacy Science (ILS) programs have been designated by ESA to develop and pursue independent science programs that capitalise on the unique data products of the Euclid surveys.

SUBSTELLAR will re-use existing ground-based and space-based multi-wavelength data to complement the new data obtained with the Euclid space mission.

PROJECT CHALLENGES

The first challenge of the project is to identify, based on Euclid data, an unprecedented large number (>106) of very low mass (VLM) stars and substellar-mass objects (SMOs), including hard to find objects such as halo brown dwarfs and young free-floating planetary-mass objects. Specific pipelines will be developed to extract the utmost information from Euclid for faint infrared objects.

The second challenge is to discover very low-mass binaries and giant planets around VLM stars and SMOs using custom-made image analysis, astrometric monitoring and spectral fitting techniques.

The third challenge is to combine the information gathered from harnessing the previous two challenges to determine the VLM stellar and substellar luminosity function, infer the most likely low-mass end of the Initial Mass Function (IMF), and explore its degree of universality in different components of the Milky Way.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The main activities of the SUBSTELLAR project have focused on the preparation, verification and exploitation of Euclid datasets for substellar science. The project PI led one of the winning proposals in ESA´s competition for the Euclid Early Release Observation (ERO) program and our first results were included among the 16 open-access papers selected for the special issue “Euclid on Sky” published by Astronomy and Astrophysics on April 30, 2025. The main achievements presented in this paper has been to identify SMO benchmarks observed by Euclid in the very young Sigma Orionis open cluster, to use them to reject or confirm candidate members from the literature, to discover new members and to estimate the Substellar IMF of this cluster reaching to lower masses than ever before.

The SUBSTELLAR postdoc Marusa Zerjal was awarded 9 hours of 8.0-meter Very Large Telescope of the European Southern Observatory (Service Mode run 114.27NZ.001) to obtain follow-up near-infrared spectroscopic observations of dozens of substellar candidates identified using Euclid ERO data in the Messier 78 dark cloud in Orion. The observations were successfully carried out with the Very Large Telescope KMOS instrument at Paranal Observatory in Chile and are under analysis.

While the SUBSTELLAR team still busy working with ERO data and preparing additional papers, our activities have expanded to the analysis of the Euclid Quick Data Release 1 (Q1). Our main achievements based on Q1 will be presented in three papers led by SUBSTELLAR postdocs and two papers led by SUBSTELLAR students. The team analysis of Euclid´s NISP slitless spectra has confirmed the presence of over 1,000 ultracool dwarfs in the three deep fields.

These spectroscopically confirmed objects allow us to estimate that there are about 10,000 ultracool dwarfs in these fields that can be detected with Euclid photometry. Detailed analysis of the Euclid images has allowed us to discover new substellar binary systems and to carry out follow up observations using ground-based telescopes such as the 10.4-meter Gran Telescopio Canarias (GTC). The project PI has already been awarded 9 nights of observing time at the GTC with the EMIR and OSIRIS instruments for follow-up observations of Euclid discovered targets. The observations were carried out in December 2024 and June 2025. The SUBSTELLAR doctoral student Sara Muñoz Torres was trained to carry out the observations in visitor mode.

In parallel to the observational work, the SUBSTELLAR activity is also pushing the frontier of knowledge in the development of theoretical models. The SUBSTELLAR student Nafise Sedighi is working in producing the next generation of synthetic spectral library for SMOs with chemical composition different than that of the Sun.

SUBSTELLAR students Styliani Tsilia and Jerry Yun-Jan Zhang successfully participated in the Vatican Observatory Summer School 2025, and SUBSTELLAR student Nafise Sedighi has participated in the Bad Honnef Physics School on Exoplanet Atmospheres in July 2025. The SUBSTELLAR team is going to have a very important participation in September 2025 at the international conference “Brown Dwarfs keep their Cool: 30 years of Substellar Science” with six oral contributions and one invited review.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The potential impact of the SUBSTELLAR results is to confirm that Euclid´s performance is exceeding expectations and that it will open a new era in many branches of Astrophysics, including Substellar science. The ERO program led by the project has inspired additional Euclid observations in the Orion giant star-forming complex that were partially released in Q1 and will be included in the first major data release (DR1) that is planned for late 2026.

The key need of the project to ensure further uptake and success is anticipated to be a one-year extension to compensate for delays with the Euclid launch and operations and to obtain follow-up observations and complete theoretical analysis. This extension will be requested in due time. The PI of the project is planning to propose to ESA that specific data products produced by the SUBSTELLAR team are included in the Euclid Quick Data Release 3 (Q3) that is scheduled for spring of 2028.

Horsehead Nebula or Barnard 33