J-PLUS: Discovery and characterisation of ultracool dwarfs using Virtual Observatory tools

¹ Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
e-mail: esm@cab.inta-csic.es
² Spanish Virtual Observatory, Spain
³ Departmento de Astrofísica, Centro de Astrobiología (CSIC-INTA), Carretera de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
⁴ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, 44001 Teruel, Spain
⁵ Donostia International Physics Centre (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
⁶ IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
⁷ Observatorio Nacional – MCTIC (ON), Rua General José Cristino, 77, São Cristóvão, 20921-400 Rio de Janeiro, Brazil
⁸ Centro de Estudios de Física del Cosmos de Aragón (CEFCA) – Unidad Asociada al CSIC, Plaza San Juan 1, 44001 Teruel, Spain
⁹ University of Michigan, Department of Astronomy, 1085 South University Ave., Ann Arbor, MI 48109, USA
¹⁰ University of Alabama, Department of Physics and Astronomy, Gallalee Hall, Tuscaloosa, AL 35401, USA
¹¹ Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹² Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, C. Universitária, 05508-090 São Paulo, Brazil
¹³ Departamento de Ciencias Físicas, Universidad Andrés Bello, Fernández Concha 700, Las Condes, Santiago, Chile
¹⁴ Departamento de Física, Universidade Federal de Sergipe, Av. Marechal Rondon, s/n. São Cristóvão, 49100-000 Sergipe, SE, Brazil
¹⁵ Center for Space Science and Technology, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
¹⁶ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
¹⁷ Physics Department, Lancaster University, C35, Bailrigg, Lancaster LA1 4YW, UK

Received: 6 February 2019
Accepted: 7 May 2019

Abstract

Context. Ultracool dwarfs are objects with spectral types equal to or later than M7. Most of them have been discovered using wide-field imaging surveys. The Virtual Observatory has proven to be very useful for efficiently exploiting these astronomical resources.

Aims. We aim to validate a Virtual Observatory methodology designed to discover and characterise ultracool dwarfs in the J-PLUS photometric survey. J-PLUS is a multiband survey carried out with the wide-angle T80Cam optical camera mounted on the 0.83 m telescope JAST/T80 in the Observatorio Astrofísico de Javalambre. We make use of the Internal Data Release covering 528 deg².

Methods. We complemented J-PLUS photometry with other catalogues in the optical and infrared using VOSA, a Virtual Observatory tool that estimates physical parameters from the spectral energy distribution fitting to collections of theoretical models. Objects identified as ultracool dwarfs were distinguished from background M giants and highly reddened stars using parallaxes and proper motions from Gaia DR2.

Results. We identify 559 ultracool dwarfs, ranging from i = 16.2 mag to i = 22.4 mag, of which 187 are candidate ultracool dwarfs not previously reported in the literature. This represents an increase in the number of known ultracool dwarfs of about 50% in the region of the sky we studied, particularly at the faint end of our sensitivity, which is interesting as reference for future wide and deep surveys such as Euclid. Three candidates are interesting targets for exoplanet surveys because of their proximity (distances less than 40 pc). We also analysed the kinematics of ultracool dwarfs in our catalogue and found evidence that it is consistent with a Galactic thin-disc population, except for six objects that might be members of the thick disc.

Conclusion. The results we obtained validate the proposed methodology, which will be used in future J-PLUS and J-PAS releases. Considering the region of the sky covered by the Internal Data Release used in this work, we estimate that 3000–3500 new ultracool dwarfs will be discovered at the end of the J-PLUS project.