NGC 628的PPAK宽场积分场光谱：I.单个星系上最大的光谱镶嵌图
PPAK Wide-field Integral Field Spectroscopy of NGC 628: I. The largest spectroscopic mosaic on a single galaxy
摘要：
本文介绍了一个宽视场的IFS观测结果，它包括11094个独立的光谱，覆盖了一个直径约6弧分的近圆形视场，在光波长范围内（3700- 7000 AA），每个光谱的采样率约为2.7弧秒。这个星系是PPAK IFS邻近星系巡天的一部分（PINGS，Rosales-Ortega等人，2009）。据我们所知，这是有史以来对单个邻近星系进行的最广泛的光谱调查。详细的流量校准，授予$\sim$\，0.2马格的分光光度精度。恒星星族的年龄显示出一个负梯度从内部（老）到外部（年轻）的地区。我们发现在中心~1 kpc区域的这种梯度的反转，在这个半径的环内存在一个稍微年轻的恒星星族。这种结构与一个在500秒差距的环核恒星形成区有关，在类似的螺旋星系中也有发现。从综合和空间分辨电离气体的研究，我们发现了一个中等的SFR ~ 2.4 Msun年$^{-1}$。氧丰度从星系内部到外部呈现明显的高金属丰度梯度，平均值为12 + log（O/H）~ 8.7。在星系的某些特定区域，物理性质的空间分辨分布显示出某种程度的结构，表明在单个\hh区域内存在真正的点对点变化。我们的结果是一致的由内而外的增长计划，与较强的恒星形成在外部地区，并与演化的恒星星族的内部。
英文摘要：
We present a wide-field IFS survey on the nearby face-on Sbc galaxy NGC 628, comprising 11094 individual spectra, covering a nearly circular field-of-view of ~6 arcmin in diameter, with a sampling of ~2.7 arcsec per spectrum in the optical wavelength range (3700--7000 AA). This galaxy is part of the PPAK IFS Nearby Galaxies Survey, (PINGS, Rosales-Ortega et al. 2009). To our knowledge, this is the widest spectroscopic survey ever made in a single nearby galaxy. A detailed flux calibration was applied, granting a spectrophotometric accuracy of $\sim$\,0.2 mag. The age of the stellar populations shows a negative gradient from the inner (older) to the outer (younger) regions. We found an inversion of this gradient in the central ~1 kpc region, where a somewhat younger stellar population is present within a ring at this radius. This structure is associated with a circumnuclear star-forming region at ~ 500 pc, also found in similar spiral galaxies. From the study of the integrated and spatially resolved ionized gas we found a moderate SFR of ~ 2.4 Msun yr$^{-1}$. The oxygen abundance shows a a clear gradient of higher metallicity values from the inner part to the outer part of the galaxy, with a mean value of 12~+~log(O/H) ~ 8.7. At some specific regions of the galaxy, the spatially resolved distribution of the physical properties show some level of structure, suggesting real point-to-point variations within an individual \hh region. Our results are consistent with an inside-out growth scheme, with stronger star formation at the outer regions, and with evolved stellar populations in the inner ones.
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