2020/11/18 by M. Messa, D. Calzetti, A. Adamo +7 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/abe0b5
29 pages (20 figures, 5 tables) + appendix (6 pages, 6 figures, 1 table). Submitted, feedback/comments are welcome
arxiv created 2020/11/18 · arxiv updated 2021/03/17
Using recently acquired HST NIR observations (J, Paβ and H bands) of the nearby galaxy NGC1313, we investigate the timescales required by a young star cluster to emerge from its natal cloud. We search for extincted star clusters, potentially embedded in their natal cloud as either: 1. compact sources in regions with high Hα/Paβ extinctions; 2. compact HII regions that appear as point-like sources in the Paβ emission map. The NUV--optical--NIR photometry of the candidate clusters is used to derive their ages, masses and extinctions via a least-χ2 SED broad and narrow--band fitting process. The 100 clusters in the final samples have masses in the range \rm log10(M/M_\odot)=2.5-3.5 and moderate extinctions, \rm E(B-V)\lesssim1.0 mag. Focusing on the young clusters (0-6 Myr) we derive a weak correlation between extinction and age of the clusters. Almost half of the clusters have low extinctions, \rm E(B-V)<0.25 mag, already at very young ages (≤3 Myr), suggesting that dust is quickly removed from clusters. A stronger correlation is found between the morphology of the nebular emission (compact, partial or absent, both in Hα and Paβ) and cluster age. Relative fractions of clusters associated with a specific nebular morphology is used to estimate the typical timescales for clearing the natal gas cloud, resulting between 3 and 5 Myr, ∼1 Myr older than what estimated from NUV--optical--based cluster studies. This difference hints to a bias for optically--only based studies, which JWST will address in the coming years.