Early-type galaxies in low-density environments: NGC 6876 explored through its globular cluster system

ENNIS, ANA I; BASSINO, LILIA P; CASO, JUAN P; DE BÓRTOLI, BRUNO J

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2019 vol. 488 p. 770 - 781

0035-8711

We presentthe results of a photometric study of the early-type galaxy NGC 6876 and thesurrounding globular cluster system (GCS). The host galaxy is a massiveelliptical, the brightest of this type in the Pavo Group. According to itsintrinsic brightness (Mv ~ -22.7), it is expected to belong to agalaxy cluster instead of a poor group. Observational material consists of g´,r´, i´ images obtained with the Gemini/GMOS camera. The selected globularcluster (GC) candidates present a clear bimodal colour distribution atdifferent galactocentric radii, with mean colours and dispersions for themetal-poor ("blue") and metal-rich ("red") typical of oldGCs. The red subpopulation dominates close to the galaxy centre, in addition tothe radial projected distribution showing that they are more concentratedtowards the galaxy centre. The azimuthal projected distribution shows anoverdensity in the red subpopulation in the direction of a trail observed inX-ray that could be evidence of interactions with its spiral neighbour NGC6872. The turn-over of the luminosity function gives an estimated distancemodulus (m - M) ≈ 33.5 and the total population amounts to 9400 GCs, i.e. aquite populous system. The halo mass obtained using the number ratio (i.e. thenumber of GCs with respect to the baryonic and dark mass) gives a total of  10^13, meaning it is a very massive galaxy,given the environment.