J-PLUS: a catalogue of globular cluster candidates around the M 81/M 82/NGC 3077 triplet of galaxies

Chies-Santos, Ana L.; de Souza, Rafael S.; Caso, Juan P.; Ennis, Ana I.; de Souza, Camila P. E.; Barbosa, Renan S.; Chen, Peng; Javier Cenarro, A.; Ederoclite, Alessandro; Cristóbal-Hornillos, David; Hernández-Monteagudo, Carlos; López-Sanjuan, Carlos; Marín-Franch, Antonio; Moles, Mariano; Varela, Jesús; Vázquez Ramió, Héctor; Dupke, Renato; Sodré, Laerte; Angulo, Raul E.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society

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Globular clusters (GCs) are proxies of the formation assemblies of their host galaxies. However, few studies exist targeting GC systems of spiral galaxies up to several effective radii. Through 12-band Javalambre Photometric Local Universe Survey (J-PLUS) imaging, we study the point sources around the M 81/M 82/NGC 3077 triplet in search of new GC candidates. We develop a tailored classification scheme to search for GC candidates based on their similarity to known GCs via a principal component analysis projection. Our method accounts for missing data and photometric errors. We report 642 new GC candidates in a region of 3.5 deg2 around the triplet, ranked according to their Gaia astrometric proper motions when available. We find tantalizing evidence for an overdensity of GC candidate sources forming a bridge connecting M 81 and M 82. Finally, the spatial distribution of the GC candidates (g - i) colours is consistent with halo/intra-cluster GCs, i.e. it gets bluer as they get further from the closest galaxy in the field. We further employ a regression-tree-based model to estimate the metallicity distribution of the GC candidates based on their J-PLUS bands. The metallicity distribution of the sample candidates is broad and displays a bump towards the metal-rich end. Our list increases the population of GC candidates around the triplet by threefold, stresses the usefulness of multiband surveys in finding these objects, and provides a testbed for further studies analysing their spatial distribution around nearby (spirals) galaxies.