论文标题
两个处女座群集星形矮星系中的倒金属性梯度：最近合并的证据？
Inverted metallicity gradients in two Virgo cluster star-forming dwarf galaxies: evidence of recent merging?
论文作者
论文摘要
我们介绍了处女座群集（VCC135和VCC324）中两个星形矮星系的整体场光谱观测值，该星系在Calar Alto 3.5米望远镜上使用PMAS/PPAK获得。我们使用N2经验校准器来得出金属图。星系显示出阳性气体金属性梯度，这与通常在其他矮人或螺旋星系中发现的梯度相反。我们的梯度斜率分别为0.20 $ \ pm $ 0.06和0.15 $ \ pm $ 0.03 dex/$ r_e $ vcc135和vcc324。仅在少数非常孤立的星系或更高的红移（$ z> $ 1）中观察到这种趋势。人们认为它与从星际培养基中的金属贫困气体积聚有关，这种机制在像处女座这样的高密度环境中的可能性较小。我们将发射线观测值与深度光学图像相结合，以研究特殊的金属性梯度的起源。星系中的潜在下结构的存在以及形态诊断和电离气体运动学的分析表明，金属贫气气体向矮人的中央区域的流入可能与最近与气体富含气体的伴侣合并事件有关。
We present integral field spectroscopy observations of two star-forming dwarf galaxies in the Virgo cluster (VCC135 and VCC324) obtained with PMAS/PPak at the Calar Alto 3.5 meter telescope. We derive metallicity maps using the N2 empirical calibrator. The galaxies show positive gas metallicity gradients, contrarily to what is usually found in other dwarfs or in spiral galaxies. We measure gradient slopes of 0.20 $\pm$ 0.06 and 0.15 $\pm$ 0.03 dex/$R_e$ for VCC135 and VCC324, respectively. Such a trend has been only observed in few, very isolated galaxies, or at higher redshifts ($z >$ 1). It is thought to be associated with accretion of metal-poor gas from the intergalactic medium, a mechanism that would be less likely to occur in a high-density environment like Virgo. We combine emission line observations with deep optical images to investigate the origin of the peculiar metallicity gradient. The presence of weak underlying substructures in both galaxies and the analysis of morphological diagnostics and of ionised gas kinematics suggest that the inflow of metal-poor gas to the central regions of the dwarfs may be related to a recent merging event with a gas-rich companion.
