对反常BCD Mrk 996的VLT VIMOS研究：电离气体运动学和丰度绘图
A VLT VIMOS study of the anomalous BCD Mrk 996: mapping the ionised gas kinematics and abundances
摘要：
利用高分辨率光学VLT VIMOS积分场单位谱学对蓝致密矮星系Mrk 996进行了研究。Mrk 996显示多分量线发射，大多数线轮廓由窄的中心高斯组成，具有基础的宽分量。宽HI Balmer分量在距核1”.5半径内分裂成两个单独的宽分量;这些归因于双臂微型螺旋。从Hα窄组分得到的Mrk 996的旋转曲线在3 kpc的半径范围内得出总质量为5 × 10^8 Msol。高激发能、高临界密度的[O III] 4363和[N II] 5755谱线仅从内部区域检测到，并且纯粹以宽分量形式存在，这意味着不寻常的激发条件。表面亮度，径向速度，和FWHM地图的几个排放组件。对宽发射线和窄发射线区域进行了单独的物理分析。我们推导出窄谱线气体的电子温度上限为10，000 K，电子密度为170 cm^-3，这是正常H II区的典型值。对于宽谱线分量，我们估计温度为11，000 K，电子密度为10^7 cm^-3。宽线发射区显示相对于窄线区的~20的N/H富集因子，但推断没有He/H、O/H、S/H或Ar/H富集。主导线激发机制是光电离的~3000 WR星和~ 150，000 O型星估计存在于核心。这确实是一个特殊的BCD，在核心有非常密集的气体区，恒星流出和可能的激波前沿渗透到这些气体区，有助于激发宽线发射。[摘要]
英文摘要：
A study of the blue compact dwarf (BCD) galaxy Mrk 996 based on high resolution optical VLT VIMOS integral field unit spectroscopy is presented. Mrk 996 displays multi-component line emission, with most line profiles consisting of a narrow, central Gaussian with an underlying broad component. The broad HI Balmer component splits into two separate broad components inside a 1".5 radius from the nucleus; these are attributed to a two-armed mini-spiral. The rotation curve of Mrk 996 derived from the Hαnarrow component yields a total mass of 5x10^8 Msol within a radius of 3 kpc. The high excitation energy, high critical density [O III] 4363 and [N II] 5755 lines are only detected from the inner region and exist purely in broad component form, implying unusual excitation conditions. Surface brightness, radial velocity, and FWHM maps for several emission components are presented. A separate physical analysis of the broad and narrow emission line regions is undertaken. We derive an upper limit of 10,000 K for the electron temperature of the narrow line gas, together with an electron density of 170 cm^-3, typical of normal H II regions. For the broad line component, we estimate a temperature of 11,000 K and an electron density of 10^7 cm^-3. The broad line emission regions show a N/H enrichment factor of ~20 relative to the narrow line regions, but no He/H, O/H, S/H, or Ar/H enrichment is inferred. The dominant line excitation mechanism is photoionisation by the ~3000 WR stars and ~150,000 O-type stars estimated to be present in the core. This is indeed a peculiar BCD, with extremely dense zones of gas in the core, through which stellar outflows and possible shock fronts permeate contributing to the excitation of the broad line emission. [Abridged]
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