The stellar initial mass function of nearby young moving groups

¹ Departamento de Astronomía, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, CP 11400, Uruguay
² Steward Observatory and Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA
³ American Museum of Natural History, 200 Central Park W, New York, NY 10024, USA
⁴ Planétarium de Montréal, Montréal, Québec, Canada
⁵ Trottier Institute for Research on Exoplanets, Université de Montréal, Département de Physique, Montréal, Québec, Canada
⁶ Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada 22800, BC, Mexico

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 30 October 2025
Accepted: 27 December 2025

Abstract

Context. The solar neighbourhood is populated by nearby (<200 pc), young (<100 Myr) moving groups (NYMGs) of stars, whose origins are still a matter of debate. One plausible explanation is that they are remnants of individual stellar clusters and associations that are currently dispersing throughout the galactic disc.

Aims. We aim to derive the initial mass function (IMF) of a large sample of NYMGs.

Methods. We developed and applied an algorithm that uses photometric and astrometric data from Gaia DR3 to detect NYMGs as over-densities in a kinematic space, whose members distribute along young isochrones. We inferred individual masses from the photometry of both the detected and the previously known candidates. We estimated the IMFs for 33 groups, 30 of them for the first time, in an average mass range 0.1 < m/M_⊙ < 5, with some groups going as low as 0.02 M_⊙ and as high as 10 M_⊙. We parameterised these IMFs using a log-normal for m < 1 M_⊙ and a power-law for m > 1 M_⊙.

Results. We detected 4166 source candidate members of 44 known groups, including 2545 new candidates. We recovered 44-54% of the literature candidates and estimated a contamination rate from old field stars of 16-24%. The candidates of the detected groups distribute along young isochrones, which suggests that they are potential members of NYMGs. Parameterisations of both the average of the 3 3 IMFs based on our detections (m_c = 0.25 ± 0.17 M_⊙, σ_c = 0.45 ± 0.17, and α = −2.26 ± 0.09) and the one based on the known candidates from the literature (m_c = 0.22 ± 0.14 M_⊙, σ_c = 0.45 ± 0.17, and α = −2.45 ± 0.06) are in agreement with the IMF parameterisation of the solar neighbourhood and young stellar associations.

Conclusions. Our parameterisation of the average IMF, together with the distribution of the detected group members along young isochrones offer strong evidence suggesting that the NYMGs are remnants of individual stellar associations and clusters. We confirm that there are no systematic biases in our detection and in the literature in the range of 0.1 < m/M_⊙ < 10.