The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B.G.; Gouliermis, D.A.; Dale, D.A.; Fumagalli, M.; Grebel, E.K.; Johnson, K.E.; Kahre, L.; Kennicutt, R.C.; Messa, M.; Pellerin, A.; Ryon, J.E.; Smith, L.J.; Shabani, F.; Thilker, D.; Ubeda, L.

doi:10.3847/1538-4357/aa6f15

The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B.G.; Gouliermis, D.A.; Dale, D.A.; Fumagalli, M.; Grebel, E.K.; Johnson, K.E.; Kahre, L.; Kennicutt, R.C.; Messa, M.; Pellerin, A.; Ryon, J.E.; Smith, L.J.; Shabani, F.; Thilker, D.; Ubeda, L.

Authors

K. Grasha

D. Calzetti

A. Adamo

H. Kim

B.G. Elmegreen

D.A. Gouliermis

D.A. Dale

Professor Michele Fumagalli michele.fumagalli@durham.ac.uk
Academic Visitor

E.K. Grebel

K.E. Johnson

L. Kahre

R.C. Kennicutt

M. Messa

A. Pellerin

J.E. Ryon

L.J. Smith

F. Shabani

D. Thilker

L. Ubeda

Abstract

We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ~40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

Citation

Grasha, K., Calzetti, D., Adamo, A., Kim, H., Elmegreen, B., Gouliermis, D., …Ubeda, L. (2017). The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies. Astrophysical Journal, 840(2), Article 113. https://doi.org/10.3847/1538-4357/aa6f15

Journal Article Type	Article
Acceptance Date	Apr 20, 2017
Online Publication Date	May 15, 2017
Publication Date	May 15, 2017
Deposit Date	May 26, 2017
Publicly Available Date	May 26, 2017
Journal	Astrophysical Journal
Print ISSN	0004-637X
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	840
Issue	2
Article Number	113
DOI	https://doi.org/10.3847/1538-4357/aa6f15