The kinematics and spatial distribution of stellar populations in E+A galaxies
The kinematics and spatial distribution of stellar populations in E+A galaxies
复制标题
DOI：
10.1111/j.1365-2966.2009.14836.x
复制
发表时间：
2009-03
影响因子：
4.8
通讯作者：
M. Pracy;H. Kuntschner;W. Couch;C. Blake;K. Bekki;F. Briggs
中科院分区：
文献类型：
--
作者：
M. Pracy;H. Kuntschner;W. Couch;C. Blake;K. Bekki;F. Briggs
我们使用8.1米双子南望远镜的双子座多目标光谱仪（GMOS）仪器获得空间分辨的双色成像和积分场单元（IFU）光谱的10个附近（z = 0.04-0.20）的“E+A”星系的样本从2度场星系红移调查。这些星系被选中位于各种环境中，从孤立的系统到丰富的星系团。使用我们的成像数据测量的表面亮度剖面显示，我们的样品的等照度剖面一般是r 1/4样的，与早期类型的星系为主的样品一致。在我们的样本中，只有一个星系在等照度线轮廓中具有明显的指数（“盘状”）分量。所有具有早期哈勃类型形态分类的星系都进一步强调了这一点，并且一旦对E+A阶段发生的短暂增亮进行校正，它们在中心速度色散-绝对星等平面上的行为与费伯-杰克逊关系一致。此外，三分之二的样本显示出正在进行的或最近的潮汐相互作用/合并的明确证据，如潮汐尾和扰动形态的存在所证明的。虽然我们样本中的所有星系都具有相对蓝色的总综合颜色（与它们的E+A状态保持一致），但它们显示出颜色梯度的多样性，拥有相对于外部区域更红，更蓝或颜色模糊的中央核心区域。E+A光谱很好地拟合了年轻恒星的光谱，年轻恒星的光是如此占主导地位，以至于不可能量化潜在的老恒星的存在。与最近的其他发现一致，几乎没有证据表明巴尔末吸收线等效宽度在中心几千秒差距（<4 kpc）内存在径向梯度，尽管由于IFU数据的空间范围有限，我们无法在更大的半乳心半径处搜索先前报告的径向梯度。在运动学上，最引人注目的特性是在我们所有的E+A星系中看到的显著而明确的旋转，它通常靠近光度长轴。这与Norton等人的发现相反，他在附近的E+A星系的一个非常相似的样本中几乎没有发现旋转的证据。我们还清楚地表明，我们的E+A星系，在所有情况下，但一种情况下，一致的是“快速走廊”，根据其内部角动量每单位质量测量的半径和椭圆率的函数。我们认为，在这些星系的扰动形态和显着的旋转相结合，支持他们的生产通过富含气体的星系合并和相互作用。大部分的快速旋转反对同等质量的合并是占主导地位的祖先的E+A人口。
We have used the Gemini Multi-Object Spectragraph (GMOS) instrument on the 8.1-m Gemini-South Telescope to obtain spatially resolved two-colour imaging and integral field unit (IFU) spectroscopy of a sample of 10 nearby (z = 0.04-0.20) 'E+A' galaxies selected from the Two Degree Field Galaxy Redshift Survey. These galaxies have been selected to lie in a variety of environments from isolated systems to rich clusters. Surface brightness profiles measured using our imaging data show the isophotal profiles of our sample are generally r 1/4 -like, consistent with a sample dominated by early-type galaxies. Only one galaxy in our sample has an obvious exponential ('disc-like') component in the isophotal profile. This is further underscored by all galaxies having early Hubble-type morphological classifications, and showing a behaviour in the central velocity dispersion-absolute magnitude plane that is consistent with the Faber―Jackson relation, once the transitory brightening that occurs in the E+A phase is corrected for. In addition, two-thirds of our sample shows clear evidence of either ongoing or recent tidal interactions/mergers, as evidenced by the presence of tidal tails and disturbed morphologies. While all the galaxies in our sample have total integrated colours that are relatively blue (in keeping with their E+A status), they show a diversity of colour gradients, possessing central core regions that are either redder, bluer or indistinct in colour relative to their outer regions. The E+A spectra are well fitted by that of a young stellar population, the light from which is so dominant that it is impossible to quantify the presence of the underlying old stellar population. Consistent with other recent findings, there is little evidence for radial gradients in the Balmer absorption line equivalent widths over the central few kiloparsecs (<4 kpc), although we are unable to search for the previously reported radial gradients at larger galactocentric radii due to the limited spatial extent of our IFU data. Kinematically, the most striking property is the significant and unambiguous rotation that is seen in all our E+A galaxies, with it being generally aligned close to the photometric major axis. This is contrary to the findings of Norton et al., who found little or no evidence for rotation in a very similar sample of nearby E+A galaxies. We also clearly demonstrate that our E+A galaxies are, in all but one case, consistent with being 'fast rotators', based on their internal angular momentum per unit mass measured as a function of radius and ellipticity. We argue that the combination of disturbed morphologies and significant rotation in these galaxies supports their production via gas-rich galaxy mergers and interactions. The large fraction of fast rotators argues against equal mass mergers being the dominant progenitor to the E+A population.