NGC185发射线布居的深谱
Deep spectroscopy of the emission-line populations in NGC185
摘要：
矮星系是了解星系形成和演化的关键，因为它们构成了最丰富的星系群。由于恒星的形成而引起的畸变比及其变化是化学演化模型的关键约束。因此，在本宇宙的矮星系中确定这些丰度是极其重要的。然而，这些物体本质上是暗淡的，只能从非常接近的星系中获得对其演化的观测约束。NGC 185是M31的四颗最亮的矮星伴星之一，但与NGC 147、NGC 205和NGC 221（M32）不同的是，它含有大量的气体和尘埃。我们在双子座用GMOS-N获得了NGC 185的H $α$发射布居的深光谱观测。因此，除了先前在银河系中发现并在文献中报道的明亮行星状星云（PNE）外，我们还发现了其他更暗的PNE。然后，我们重新计算了最亮的电子的电子温度和化学丰度，并首次推导出它们的电子密度。我们的PN人口属性的特征解释的NGC 185的化学演化，这表明它已经遭受了显着的化学富集在过去的$\sim$ 8 Gyr。我们还发现了银河系中的第一颗共生星，并揭示了位于NGC 185中心附近的已知超新星遗迹的性质。
英文摘要：
Dwarf galaxies are crucial to understand the formation and evolution of galaxies, since they constitute the most abundant galaxy population. Abundance ratios and their variations due to star formation are key constraints to chemical evolution models. The determination of these abundances in the dwarf galaxies of the Local Universe is thus of extreme importance. However, these objects are intrinsically faint and observational constraints to their evolution can be obtained only for very nearby galaxies. NGC 185 is one of the four brightest dwarf companions of M31, but unlike than the other three, NGC 147, NGC 205, and NGC 221 (M32) it has an important content of gas and dust. We obtained deep spectroscopic observations of the H$α$ emitting population of NGC 185 using GMOS-N at Gemini. As a result, in addition to the bright planetary nebulae (PNe) previously found in the galaxy and reported in the literature, we found other, much fainter, PNe. We then re-calculated the electron temperatures and chemical abundances of the brightest ones, and derived, for the first time, their electron densities. Our characterisation of the PN population properties is interpreted in terms of the chemical evolution of NGC 185, which suggests that it has suffered a significant chemical enrichment within the last $\sim$8 Gyr. We also discovered the first symbiotic star in the galaxy and enlightened the properties of a known supernova remnant located close to the centre of NGC 185.
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