论文标题

在NCG 1313中寻找模糊的年轻明星簇

Looking for obscured young star clusters in NCG 1313

论文作者

Messa, M., Calzetti, D., Adamo, A., Grasha, K., Johnson, K. E., Sabbi, E., Smith, L. J., Bajaj, V., Finn, M. K., Lin, Z.

论文摘要

使用最近获得的HST NIR观测值(J,PA $β$和H频段),我们研究了一个年轻的星团从其出生云中浮出水面所需的时间表。我们搜索已灭绝的星形簇,可能会嵌入其出生云中:1。h $α$/pa $β$灭绝的地区的紧凑源; 2。紧凑型HII区域,在PA $β$发射图中作为点样源出现。候选群集的NUV(光学 - 光度法)用于通过至少$-χ^2 $ sed宽和狭窄的贴合过程来得出其年龄,质量和灭绝。最终样本中的100个簇在范围内的质量$ \ rm \ log_ {10}(m/m_ \ odot)= 2.5-3.5 $和中度灭绝,$ \ rm e(b-v)\ lysesim1.0 $ mag。 专注于年轻的集群($ 0-6 $ MYR),我们得出了灭绝与年龄之间的弱相关性。几乎一半的簇具有低灭绝的损失,$ \ rm E(B-V)<0.25 $ mag已经很年轻($ \ le3 $ MYR),这表明从集群中迅速清除了灰尘。在h $α$和pa $β$中的变形(紧凑,部分或不存在)与群集年龄之间发现了更强的相关性(紧凑,部分或不存在)。 与特定的螺旋形态相关的簇的相对部分用于估计清除静态气云的典型时间尺度,导致3至5 Myr,$ \ sim1 $ myr比根据基于光学的群集研究的估计。这种差异暗示了光学上仅基于基于的研究,JWST将在未来几年中解决。

Using recently acquired HST NIR observations (J, Pa$β$ 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 H$α$/Pa$β$ extinctions; 2. compact HII regions that appear as point-like sources in the Pa$β$ emission map. The NUV--optical--NIR photometry of the candidate clusters is used to derive their ages, masses and extinctions via a least$-χ^2$ SED broad and narrow--band fitting process. The 100 clusters in the final samples have masses in the range $\rm \log_{10}(M/M_\odot)=2.5-3.5$ 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 ($\le3$ 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 H$α$ and Pa$β$) 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, $\sim1$ 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.

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