极环星系IIZw71多重结的长缝分光光度研究
Long-slit spectrophotometry of the multiple knots of the polar ring galaxy IIZw71
摘要：
我们进行了长缝光谱观测的恒星形成结沿极环的矮星系IIZw 71在光谱范围3500 - 10000埃采取的威廉厄歇尔望远镜（WHT）。光谱观测得到了可用的窄Halpha滤波器中星系光度测量的补充。我们测量了环的自转曲线，由此推断成星环内部的M/L_B = 3.9。我们测量了极光[OIII]线在两个最亮的结，使我们能够测量氧，硫，氮，氩和氖的化学丰度以下的直接方法。使用不同的经验校准器来估计最微弱的两个结中的氧丰度。获得的金属丰度是非常相似的所有节点，但低于以前在文献中报道的综合光谱。N/O丰度，从N2 O2参数，是显着恒定的环，表明当地的污染过程是不显眼的。使用STARLIGHT程序计算的合成恒星星族（SSP），我们研究了每个节点中恒星星族的年龄分布，发现在所有这些节点中，都有一个非常年轻的小于1000万年的人口，负责气体的电离，与其他人口超过10000万年，可能负责节点的化学演化。金属丰度和年龄分布在不同的节点之间的微小差异表明了一个共同的化学演化，可能与同伴星系IIZw 70的相互作用过程有关。
英文摘要：
We carried out long-slit spectroscopic observations of the star forming knots along the polar ring of the dwarf galaxy IIZw71 in the spectral range 3500 - 10000 angstroms taken with the William erschel Telescope (WHT). The spectroscopic observations were complemented with available photometry of the galaxy in the narrow Halpha filter. We measured the rotation curve of the ring, from which we infer a ratio M/L_B = 3.9 inside the star forming ring. We measured the auroral [OIII] line in the two brightest knots, allowing us to measure oxygen, sulphur, nitrogen, argon and neon chemical abundances following the direct method. Different empirical calibrators were used to estimate the oxygen abundance in the two faintest knots. The metallicities obtained are very similar for all the knots, but lower than previously reported in the literature from integrated spectra. The N/O abundance, as derived from the N2O2 parameter, is remarkably constant over the ring, indicating that local polution processes are not conspicuous. Using synthetic stellar populations (SSPs) calculated with the code STARLIGHT, we studied the age distribution of the stellar populations in each knot, finding that in all of them there is a combination of a very young population with less than 10 Myr, responsible for the ionisation of the gas, with other populations older than 100 Myr, probably responsible for the chemical evolution of the knots. The small differences in metallicity and the age distributions among the different knots are indicative of a common chemical evolution, probably related to the process of interaction with the companion galaxy IIZw70.
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