双子座IFU观测的环核恒星形成区年龄和金属丰度
Ages and metallicities of circumnuclear star formation regions from Gemini IFU observations
摘要：
目的：本文计算了旋涡星系NGC 6951和NGC 1097的环核恒星形成区的年龄和金属丰度，并探讨了这些区域的发射谱线相当低的原因。研究方法：我们使用Gemini GMOS-IFU获得的光学二维光谱数据和光电离模型网格来推导CNSFR的金属丰度和年龄。结果如下：我们发现恒星形成率在0.002-0.14 Msun/yr范围内，氧丰度为12+log（O/H）~8.8 dex，类似于位于银盘内部区域的大多数富金属星云。结论：我们的结论是，在CNSFR中观察到的非常低的发射线等效宽度是由连续谱的“污染”造成的，污染是由（1）底层凸起连续谱的贡献与（2）CNSFR中以前恒星形成的贡献相结合造成的。
英文摘要：
Aims: We derive the age and metallicity of circumnuclear star formation regions (CNSFRs) located in the spiral galaxies NGC6951 and NGC1097, and investigate the cause of the very low equivalent widths of emission lines found for these regions. Methods: We used optical two-dimensional spectroscopic data obtained with Gemini GMOS-IFUs and a grid of photoionization models to derive the the metallicities and ages of CNSFRs. Results: We find star formation rates in the range 0.002-0.14 Msun/yr and oxygen abundance of 12+log(O/H)~8.8 dex, similar to those of most metal-rich nebulae located in the inner region of galactic disks. Conclusions: We conclude that the very low emission-line equivalent widths observed in CNSFRs are caused by the ``contamination'' of the continuum by (1) contribution of the underlying bulge continuum combined with (2) contribution from previous episodes of star formation at the CNSFRs.
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