ABSTRACT

We investigate interaction effects in the stellar and gas kinematics, stellar population, and ionized gas properties of the interacting galaxy pair AM 1204−292,composed of NGC 4105 and NGC 4106. The data consist of long-slit spectra in the range 3000–7050 Å. The massive E3 galaxy NGC 4105 presents a flat stellar velocity profile, while the ionized gas is in strong rotation, suggesting an external origin. Its companion, NGC 4106, shows asymmetries in the radial velocity field, likely due to the interaction. The dynamics of the interacting pair were modelled using the P-Gadget3 treepm/sph code, from which we show that the system has just passed the first perigalacticum, which triggered an outbreak of star formation, currently at full maximum. We characterized the stellar population properties using the stellar population synthesis code starlight and, on average, both galaxies are predominantly composed of old stellar populations. NGC 4105 has a slightly negative age gradient, comparable with that of the most massive elliptical galaxies, but a steeper metallicity gradient. The SB0 galaxy NGC 4106 presents smaller radial variations in both age and metallicity in comparison with intermediate-mass early-type galaxies. These gradients have not been disturbed by interaction, since the star formation happened very recently and was not extensive in mass. Electron density estimates for the pair are systematically higher than those obtained in isolated galaxies. The central O/H abundances were obtained from photoionization models in combination with emission-line ratios, which resulted in 12 + log(O/H) = 9.03 ± 0.02 and 12 + log(O/H) = 8.69 ± 0.05 for NGC 4105 and NGC 4106, respectively.

中文翻译：

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相互作用系统AM 1204-292的物理性质和演变

摘要

我们研究了相互作用星系对AM 1204-292中由NGC 4105和NGC 4106组成的恒星和气体运动学，恒星种群和电离气体性质中的相互作用效应。数据包括3000-7050范围内的长缝光谱一种。巨大的E3星系NGC 4105呈现出平坦的恒星速度分布，而电离的气体强烈旋转，表明是外部起源。它的伴星NGC 4106可能由于相互作用而在径向速度场中显示不对称性。使用P-Gadget3 treepm / sph对相互作用对的动力学进行建模代码，从中我们可以看到系统刚刚通过了第一个银河系周，引发了恒星形成的爆发，目前已达到最大值。我们使用恒星族合成代码星光来表征恒星族属性而且，平均而言，两个星系均主要由古老的恒星族组成。NGC 4105的年龄梯度略微为负，可与大多数大型椭圆星系相提并论，但金属性梯度则较陡。与中等质量早期星系相比，SB0星系NGC 4106在年龄和金属性上都表现出较小的径向变化。这些梯度没有受到相互作用的干扰，因为恒星的形成是最近才发生的，并且质量并不广泛。该对电子密度的估计值系统地高于孤立星系中的电子密度估计值。中心O / H丰度是通过光电离模型与发射谱线比率获得的，得出NGC 4105的12 + log（O / H）= 9.03±0.02和12 + log（O / H）= 8.69±0.05和NGC 4106。