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- Menon, Shyam H., et al.
(författare)
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The dependence of the hierarchical distribution of star clusters on galactic environment
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 507:4, s. 5542-5566
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Tidskriftsartikel (refereegranskat)abstract
- We use the angular two-point correlation function (TPCF) to investigate the hierarchical distribution of young star clusters in 12 local (3–18 Mpc) star-forming galaxies using star cluster catalogs obtained with the Hubble Space Telescope (HST) as part of the Treasury Program Legacy ExtraGalactic UV Survey. The sample spans a range of different morphological types, allowing us to infer how the physical properties of the galaxy affect the spatial distribution of the clusters. We also prepare a range of physically motivated toy models to compare with and interpret the observed features in the TPCFs. We find that, conforming to earlier studies, young clusters (T≲10Myr) have power-law TPCFs that are characteristic of fractal distributions with a fractal dimension D2, and this scale-free nature extends out to a maximum scale lcorr beyond which the distribution becomes Poissonian. However, lcorr, and D2 vary significantly across the sample, and are correlated with a number of host galaxy physical properties, suggesting that there are physical differences in the underlying star cluster distributions. We also find that hierarchical structuring weakens with age, evidenced by flatter TPCFs for older clusters (T≳10Myr), that eventually converges to the residual correlation expected from a completely random large-scale radial distribution of clusters in the galaxy in ∼100Myr. Our study demonstrates that the hierarchical distribution of star clusters evolves with age, and is strongly dependent on the properties of the host galaxy environment.
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| 2. |
- Messa, Matteo, et al.
(författare)
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Looking for Obscured Young Star Clusters in NGC 1313
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 909:2
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Tidskriftsartikel (refereegranskat)abstract
- Using recently acquired Hubble Space Telescope NIR observations (J, Pa beta, and H bands) of the nearby galaxy NGC 1313, 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 H alpha/Pa beta extinctions or (2) compact H II regions that appear as point-like sources in the Pa beta emission map. The NUV-optical-NIR photometry of the candidate clusters is used to derive their ages, masses, and extinctions via a least-chi(2) spectral energy distribution broad- and narrowband fitting process. The 100 clusters in the final samples have masses in the range log10(M M-circle dot) = 2.5-3.5 and moderate extinctions, E(B - V) less than or similar to 1.0 mag. Focusing on the young clusters (0-6Myr), we derive a weak correlation between extinction and age of the clusters. Almost half of the clusters have low extinctions, E(B - V) < 0.25 mag, already at very young ages (<= 3Myr), 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 H alpha and Pa beta) and cluster age. Relative fractions of clusters associated with a specific nebular morphology are used to estimate the typical timescales for clearing the natal gas cloud, resulting in between 3 and 5Myr, similar to 1Myr older than what was estimated from NUV-optical-based cluster studies. This difference hints at a bias for optical-only-based studies, which James Webb Space Telescope will address in the coming years.
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