耗散对合并残余LOSVDs形状的影响
The imprint of dissipation on the shapes of merger remnant LOSVDs
摘要：
椭圆星系的性质与螺旋星系之间富含气体合并的模拟残留物大致一致，这激发了对这种形成机制对残留物分布函数的影响进行更详细的研究。气体对合并残余物的视线速度分布（LOSVD）的非高斯形状有很大的影响，这是由于在合并过程中保留角动量的气体形成的嵌入盘，以及落在中心的气体的强中心质量浓度。与高斯性的偏差由高斯-厄米矩h_3和h_4参数化，这与LOSVD的偏度和峰度有关。利用Gadget-2模拟，包括恒星形成、辐射冷却以及超新星和活动星系核的反馈，我们量化了（h_3，h_4）-v/sigma关系对1：1合并中原始盘初始气体分数的依赖性.对于气体分数f_gas < ~15%，h_3和v/sigma之间的整体相关性较弱，由边缘视角引起的平坦负相关分量加上正面投影引起的陡峭正相关部分组成。随着气体分数从0增加到15%，v/sigma值的分布向高正h_4减小，并且有向低h_4减小的趋势。当f_gas > ~20%时，（h_3，4）- v/sigma分布看起来完全不同--h_3- v/sigma存在紧密的负相关，在所有h_4处v/sigma值分布很广，与观测结果更一致。高f_气体残余物的再合并（干合并）产生具有接近高斯LOSVD的缓慢旋转系统。我们解释所有这些趋势的残留物的基本轨道结构，塑造他们的耗散形成的历史。
英文摘要：
The properties of elliptical galaxies are broadly consistent with simulated remnants of gas-rich mergers between spirals, motivating more detailed studies of the imprint of this formation mechanism on the remnant distribution function. Gas has a strong impact on the non-Gaussian shapes of the line-of-sight velocity distributions (LOSVDs) of the merger remnant, owing to the embedded disk that forms out of the gas that retains its angular momentum during the merger, and the strong central mass concentration from the gas that falls to the center. The deviations from Gaussianity are parametrized by the Gauss-Hermite moments h_3 and h_4, which are related to the skewness and kurtosis of the LOSVDs. We quantify the dependence of the (h_3,h_4)-v/sigma relations on the initial gas fraction of the progenitor disks in 1:1 mergers, using Gadget-2 simulations including star formation, radiative cooling, and feedback from supernovae and AGN. For gas fractions f_gas < ~15% the overall correlation between h_3 and v/sigma is weak, consisting of a flat negatively correlated component arising from edge-on viewing angles plus a steep positively correlated part from face-on projections. The spread in v/sigma values decreases toward high positive h_4, and there is a trend toward lower h_4 as the gas fraction increases from 0 to 15%. For f_gas > ~20% the (h_3,4)- v/sigma distributions look quite different - there is a tight negative h_3- v/sigma correlation, and a wide spread in v/sigma values at all h_4, in better agreement with observations. Re-mergers of the high-f_gas remnants (dry mergers) produce slowly rotating systems with nearly Gaussian LOSVDs. We explain all of these trends in terms of the underlying orbit structure of the remnants, as molded by their dissipative formation histories.
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