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Tracing the outer disk of NGC 300: An ultraviolet view
Journal of Astrophysics and Astronomy ( IF 1.1 ) Pub Date : 2019-08-01 , DOI: 10.1007/s12036-019-9603-4
Chayan Mondal , Annapurni Subramaniam , Koshy George

We present an ultra-violet (UV) study of the galaxy NGC~300 using GALEX far-UV (FUV) and near-UV (NUV) observations. We studied the nature of UV emission in the galaxy and correlated it with optical, H~I and mid-infrared (3.6 $\mu$m) wavelengths. Our study identified extended features in the outer disk, with the UV disk extending up to radius 12 kpc ($>$2R$_{25})$. We estimated the FUV and NUV disk scale-length as 3.05$\pm$0.27 kpc and 2.66$\pm$0.20 kpc respectively. The scale-length in FUV is 2.3 times larger than that at 3.6 $\mu$m, and we also find the disk to gradually become flatter from longer to shorter wavelengths. We performed a statistical source subtraction to eliminate the background contaminants and identified 261 unresolved UV sources between the radii 5.3 kpc and 10 kpc (1 $\sim$ 2 R$_{25}$). The identified UV sources show an age range between 1 - 300 Myr with a peak at 25 Myr and a mass range between $10^3 M_{\odot}$ to $10^6 M_{\odot}$, estimated using starburst99 models. The north-eastern spiral arm is found to be populated by young low mass sources suggesting that the star formation in this spiral arm is a recent phenomenon. The UV emission beyond the R$_{25}$ radius has contribution from these low mass sources and is extended up to $\sim$ 2R$_{25}$ radius. We conclude that NGC~300 has an extended UV disk, mainly populated by young low mass sources. The star formation rate is measured to be $\sim$0.46 $M_{\odot}/yr$ which is comparable to its near optical twin M33.

中文翻译:

追踪NGC 300的外盘:紫外线视图

我们使用 GALEX 远紫外 (FUV) 和近紫外 (NUV) 观测对星系 NGC~300 进行了紫外 (UV) 研究。我们研究了星系中紫外线发射的性质,并将其与光学、H~I 和中红外 (3.6 $\mu$m) 波长相关联。我们的研究确定了外盘的扩展特征,紫外线盘延伸到半径 12 kpc ($>$2R$_{25})$。我们估计 FUV 和 NUV 磁盘尺度长度分别为 3.05$\pm$0.27 kpc 和 2.66$\pm$0.20 kpc。FUV 中的尺度长度是 3.6 $\mu$m 的 2.3 倍,我们还发现圆盘从更长的波长到更短的波长逐渐变平。我们进行了统计源减法以消除背景污染物,并在半径 5.3 kpc 和 10 kpc (1 $\sim$ 2 R$_{25}$) 之间确定了 261 个未解析的紫外线源。确定的紫外线源显示年龄范围在 1 - 300 Myr 之间,峰值为 25 Myr,质量范围在 $10^3 M_{\odot}$ 至 $10^6 M_{\odot}$ 之间,使用 starburst99 模型估计。发现东北螺旋臂上有年轻的低质量源,这表明该螺旋臂中的恒星形成是最近出现的现象。超出 R$_{25}$ 半径的紫外线辐射有来自这些低质量源的贡献,并扩展到 $\sim$ 2R$_{25}$ 半径。我们得出结论,NGC~300 有一个扩展的 UV 盘,主要由年轻的低质量源填充。恒星形成率测量为 $\sim$0.46 $M_{\odot}/yr$,与它的近光学孪生 M33 相当。发现东北螺旋臂上有年轻的低质量源,这表明该螺旋臂中的恒星形成是最近出现的现象。超出 R$_{25}$ 半径的紫外线辐射有来自这些低质量源的贡献,并扩展到 $\sim$ 2R$_{25}$ 半径。我们得出结论,NGC~300 有一个扩展的 UV 盘,主要由年轻的低质量源填充。恒星形成率测量为 $\sim$0.46 $M_{\odot}/yr$,与它的近光学孪生 M33 相当。发现东北螺旋臂上有年轻的低质量源,这表明该螺旋臂中的恒星形成是最近出现的现象。超出 R$_{25}$ 半径的紫外线辐射有来自这些低质量源的贡献,并扩展到 $\sim$ 2R$_{25}$ 半径。我们得出结论,NGC~300 有一个扩展的 UV 盘,主要由年轻的低质量源填充。恒星形成率测量为 $\sim$0.46 $M_{\odot}/yr$,与它的近光学孪生 M33 相当。主要由年轻的低质量来源居住。恒星形成率测量为 $\sim$0.46 $M_{\odot}/yr$,与它的近光学孪生 M33 相当。主要由年轻的低质量来源居住。恒星形成率测量为 $\sim$0.46 $M_{\odot}/yr$,与它的近光学孪生 M33 相当。
更新日期:2019-08-01
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