Star formation history of early-type galaxies in low density environments - II. Kinematics
Star formation history of early-type galaxies in low density environments - II. Kinematics
复制标题
低密度环境中早期型星系的恒星形成历史 - II.
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
C. Chiosi
中科院分区：
文献类型：
--
作者：
M. Longhetti;R. Rampazzo;A. Bressan;C. Chiosi
这篇论文是另外两篇论文的伴侣，一篇致力于测量谱线强度指数（Longhetti et al. 1997a），另一篇致力于通过比较观测到的指数和新的光谱光度模型的预测来追溯早期星系样本的恒星形成历史（Longhetti et al. 1997b）。51个低密度环境中的早期星系样本由两个星系子集组成：Malin & Carter（1983）星表中的21个壳星系（其中一个显示双核，被认为是两个独立的天体）和Reduzzi & Rampazzo（1995）星表中的30个孤立相互作用对成员。大多数物体都显示出精细的结构。本文收集了核的运动数据，以及恒星和气体组分的速度和速度色散曲线，这些曲线与星系中心的距离有关。星系的日心系统速度与RC3的数据比较在km s-1以内，而它们的中心速度色散分别与Gonzalez（1993）、Davies等人（1987）和Carter等人（1988）的数据比较在km s-1、km s-1和km s-1以内。讨论了我们的速度和速度色散曲线与一些作者的速度和速度色散曲线的详细比较。22个壳星系核中有9个显示出发射线，其中4个，根据文献中的数据，具有liner特征的线比。30对中有10对显示发射线。RR 331a有一个类似塞弗特的核，而其余星系的([O III] λ 5007)/Hβ比率是低电离区的特征。在一小部分物体中，发射分量可以在中心值之外检测到。样本中没有一个物体显示出气体和恒星成分的反向旋转。这两个组成部分似乎是相互关联的，尽管有证据表明，在两个例子中，气体和恒星位于不同的平面上。后一种现象可能与吸积事件有关。RR 331a中央部分的发射谱线显示了发射谱线剖面中的次级成分。e2400100有两个核嵌在星系的主体中。恒星速度曲线的u型曲线显示了两个原子核持续的相互作用。最后，结合壳星系的吸积/合并起源假说，讨论了壳星系的轮廓。
The present paper is a companion of two others dedicated one to the measurement of the line–strength indices (Longhetti et al. 1997a) and the second to trace back the star formation history of a sample of early–type galaxies by comparing observed indices to the predictions of new spectro–photometric models (Longhetti et al. 1997b). The sample of 51 early-type galaxies in low density environments is composed of two sub-sets of galaxies: 21 shell galaxies from the Malin & Carter (1983) catalogue (one of which shows double nucleous and has been considered as two separate objects) and 30 members of isolated interacting pairs from the Reduzzi & Rampazzo (1995) catalogue. Most of the objects show fine structures. The paper collects nuclear kinematic data together with the velocity and velocity dispersion curves of the stellar and gaseous components as a function of the distance from the galaxies centres. The galaxies heliocentric systemic velocity compares within km s-1 with RC3 data, while their central velocity dispersion compares within km s-1 , km s-1 and km s-1 with Gonzalez (1993), Davies et al. (1987) and Carter et al. (1988) respectively. The detailed comparison between our velocity and velocity dispersion curves and those from several authors is discussed. 9 out of 22 shell galaxies nuclei show emission lines, 4 of which, using data in the literature, have line ratios characteristic of LINERs. 10 members of pairs out of 30 show emission lines. RR 331a has a Seyfert like nucleus, while for the remaining galaxies the ([O III] λ 5007)/Hβ ratio is characteristic of low ionization regions. In a small fraction of the objects the emission component is detectable outside the central value. None of the objects in the sample shows counter-rotation of the gaseous versus the stellar component. The two components appear associated, although, in two cases there is evidence that gas and stars lie on different planes. This latter phenomenon could be associated to accretion events. Emission lines in the central part of the RR 331a show a secondary component in the emission lines profile. E 2400100 has two nuclei embedded in the main body of the galaxy. The U-shape profile of the stellar velocity profile shows the ongoing interaction of the two nuclei. profile of shell galaxies is, finally, discussed in relation to the hypothesis of the accretion/merging origin of these galaxies.