IONIZED GAS IN SPIRAL AND IRREGULAR GALAXIES
IONIZED GAS IN SPIRAL AND IRREGULAR GALAXIES
复制标题
螺旋星系和不规则星系中的电离气体
DOI：
10.1086/147313
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发表时间：
1962
期刊：
影响因子：
--
通讯作者：
G. Burbidge
中科院分区：
文献类型：
--
作者：
E. Burbidge;G. Burbidge
本文描述了30多个旋涡星系和不规则星系的电离气体分布。从比较估计的相对强度的H α和STAN/分II！λ 6583的相对强度计算，得出的结论是，在星系的外部和旋臂，其中H α/STANII！λ 6583比值为-3，类似于该星系中的扩展H /sub II/ is区。研究证实了不规则星系的电离气体含量最高，并且通过SBc和SBb型的棒旋和Sc、Sbc、Sb和Sa型的正常旋，电离气体含量逐渐降低。在整个不规则星系中，在SBc和SBb星系以及某些Sbc和Sc星系的核和旋臂区域中，一定有相当数量的大质量发光恒星。其他Sc和Sbc星系的核和大多数Sb星系的核含有较少的电离气体比做螺旋臂区域。最引人注目的观测结果是，在许多后者星系的外部和核区域之间，H α和STAN/sub II/的强度比！λ 6583从约3减小到-1至0.1。这种反转在具有大的突出核和发达的核凸起的Sb和Sa星系中最为常见，但它出现在具有小核的Sc星系中。这可以用这些区域氢的普遍缺乏来解释，也可以用这样的假设来解释：在那些光主要来自K巨星的原子核中，辐射过程相对不重要，碰撞电离和激发发生在电子温度为20000 ~ 40000度的气体中，或者具有几个电子伏特的能量，因为这种激发可能是非热的。这些激发条件可能来自恒星的微粒辐射。这种对反常比率的解释是否被接受取决于主要通过线发射来维持如此高的电子温度以对抗冷却所需的能量供应的估计。这需要绝对测量发射线强度。（auth）«少
The distribution of ionized gas as deduced from the emission lines seen using the nebular spectrograph is described for more than 30 spiral and irregular galaxies. From the comparison of estimates of the relative intensities of H alpha and STAN/sub II! lambda 6583, with relative intensities computed by the usual techniques, it is concluded that the major regions of emission in the outer- parts of galaxies and in the spiral arms, where the H alpha /STANII! lambda 6583 ratio is --3, are similar to the extended H /sub II/ is regions in this galaxy. The investigation has substantiated the result that irregular galaxies have the highest propontion of ionized gas and that this decreases steadily through barred spirals of types SBc and SBb and normal spirals of types Sc, Sbc, Sb, and Sa. Throughout irregular galaxies and in the nuclear, as well as the spiral-arm, regions of SBc and SBb galaxies and some Sbc and Sc galaxies, there must be a considerable population of massive luminous stars. The nuclei of other Sc and Sbc galaxies and the nuclei in the majority of Sb galaxies contain less ionized gas than do the spiral-arm regions. The most striking observational result is thatmore » between the outer parts and the nuclear regions in many of the latter galaxies, the ratio of the strengths of H alpha and STAN/sub II/! lambda 6583 decreases from about 3 to --1 to 0.1. This reversal is most common in Sb and Sa galaxies having large prominent nuclei and well-developed nuclear bulges, but it appears in Sc galsxies having small nuclei. This can be explained either by a general deficiency of hydrogen in these regions or by supposing that radiative processes are comparatively unimportant in those nuclei where the light comes mainly from K giants, and that collisional ionization and excitation take place in the gas at an electron temperature of 20000 to 40000 deg , or having energies of a few electron volts, since such excitation may be non-thermal. These excitation conditions might arise through corpuscular radiation from stars. Whether such an explanation for the anomalous ratios is accepted depends on estimates of the energy supply required to maintain such a high electron temperature against cooling mainly by line emission. This requires absolute measurement of emission-line intensities. (auth)« less