The young stellar population in NGC 247. Main properties and hierarchical clustering

MARIA JIMENA RODRIGUEZ; GUSTAVO BAUME; CARLOS FEINSTEIN

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2019 vol. 626

0004-6361

Aims. We seek to investigate the characteristics of the young stellar population in the spiral galaxy NGC 247. In particular, we focusedour attention in its hierarchical clustering distributions and the properties of the smallest groups.Methods. We used multiband Hubble Space Telescope (HST) data from three fields covering more than half of NGC 247 to selectthe young population. Then, through the path linkage criterion (PLC), we found compact young star groups and estimated theirfundamental parameters, such as their stellar densities, sizes, number of members, and luminosity function (LF) slopes. We alsoperformed a fractal analysis to determinate the clustering properties of this population. We built a stellar density map and dendrogramscorresponding to the galactic young population to detect large structures and depict their main characteristics.Results. We detect 339 young star groups, for which we compute a mean radius of ∼ 60 pc and a maximum size distribution between30 and 70 pc. We also obtain LF slopes with a bimodal distribution showing peaks at ∼ 0.1 and ∼ 0.2. We identify several candidatesfor HII regions that follow an excellent spatial correlation with the young groups found by the PLC. We observe that the youngpopulations are hierarchically organized, wherein the smaller and denser structures are within larger and less dense structures. Wenotice that all these groups present a fractal subclustering, following the hierarchical distribution observed in the corresponding stellardensity map. For the large young structures observed in this map, we obtain a fractal dimension of ∼ 1.6-1.8 using the perimeter-arearelation and cumulative size distribution. These values are consistent with a scenario of hierarchical star formation.