J-PLUS: Reconstructing the Milky Way disc's star formation history with 12-filter photometry

¹ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, 44001 Teruel, Spain
² Instituto de Astrofísica de Andalucía - Consejo Superior de Investigaciones Científicas (IAA-CSIC), Glorieta de la Astronomía S/N, 18008 Granada, Spain
³ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
⁴ NSF NOIRLab, Tucson, AZ 85719, USA
⁵ Department of Astronomy, Beijing Normal University, Beijing, 100875, PR China
⁶ Universidade Federal do Rio de Janeiro, Observatório do Valongo, Ladeira do Pedro Antônio, 43, Saúde CEP 20080-090 Rio de Janeiro, RJ, Brazil
⁷ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia, Michoacán 58089, Mexico
⁸ Unidad Asociada CEFCA-IAA, CEFCA, Unidad Asociada al CSIC por el IAA y el IFCA, Plaza San Juan 1, 44001 Teruel, Spain
⁹ Instituto de Astrofísica de Canarias, La Laguna, 38205 Tenerife, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, 38206 Tenerife, Spain
¹¹ Observatório Nacional - MCTI (ON), Rua Gal. José Cristino 77, São Cristóvão, 20921-400 Rio de Janeiro, Brazil
¹² University of Michigan, Department of Astronomy, 1085 South University Ave., Ann Arbor, MI 48109, USA
¹³ Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, 05508-090 São Paulo, Brazil
¹⁴ Donostia International Physics Centre (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
¹⁵ IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain

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

Received: 28 August 2025
Accepted: 26 November 2025

Abstract

Context. Wide-field, multi-filter photometric surveys enable the reconstruction of the Milky Way’s star formation history (SFH) on Galactic scales and provide complementary insights into disc assembly. The 12-filter system of the Javalambre Photometric Local Universe Survey (J-PLUS) is particularly suitable, as its colours trace stellar chemical abundances and help mitigate the age-metallicity degeneracy in colour-magnitude diagram fitting.

Aims. We aim to recover the SFH of the Milky Way disc and separate its chemically distinct components by combining J-PLUS DR3 photometry with Gaia astrometry. We also intend to test the potential of isochrone fitting to estimate ages and metallicities for individual stars as proxies for disc evolutionary trends.

Methods. We fitted magnitudes and parallaxes of 1.38 × 10⁶ stars using a Bayesian multiple-isochrone technique. The bright region of the colour-absolute-magnitude diagram (M_r ≤ 4.2 mag) constrains stellar ages, while the faint region provides an empirical metallicity prior that mitigates the age-metallicity degeneracy. Both PARSEC and BaSTI isochrones, in solar-scaled and α-enhanced versions, were adopted.

Results. The recovered SFH shows two sequences: an α-enhanced population forming rapidly between 12.5 and 8 Gyr ago, enriching from [M/H]~ −0.6 to 0.1 dex; and a solar-scaled sequence emerging ∼8 Gyr ago, dominating after ∼7 Gyr with slower enrichment and reaching solar metallicity by 3 Gyr. Metal-rich ([M/H] > 0) stars are confined to |z_GC| ≲ 1 kpc, whereas metal-poor ([M/H] < -0.5) stars reach |z_GC| ~ 2 kpc.

Conclusions. Simultaneous fitting of solar-scaled and α-enhanced isochrones reveals distinct formation epochs for the thin and thick discs. J-PLUS multi-filter photometry, combined with Gaia parallaxes, effectively mitigates age-metallicity degeneracies and enables detailed mapping of the Milky Way’s temporal and chemical evolution.