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THE IMPRINT OF DISSIPATION ON THE SHAPES OF MERGER REMNANT LOSVDs

机译:合并残余农具形状的耗散问题

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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 effectively parameterized 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/σ relations on the initial gas fraction f gas of the progenitor disks in 1:1 mergers, using Gadget-2 simulations including star formation, radiative cooling, and feedback from supernovae and active galactic nuclei. For f gas 15%, the overall correlation between h 3 and v/σ is weak, consisting of a flat negatively correlated component arising from edge-on viewing angles plus a steep positively correlated part from more face-on projections. The spread in v/σ values decreases toward high positive h 4, and there is a trend toward lower h 4 values as f gas increases from 0% to 15%. For f gas 20%, the (h 3, h 4)-v/σ distributions look quite different—there is a tight negative h 3-v/σ correlation, and a wide spread in v/σ values at all h 4, in much better agreement with observations. Re-mergers of the high-f gas remnants (representing dry mergers) produce slowly rotating systems with near-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.
机译:椭圆星系的性质与螺旋之间富含气体的合并的模拟残余物大致相符,从而促使人们更详细地研究这种形成机制对残余物分布函数的影响。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影响,这是由于气体中形成的嵌入式磁盘在合并过程中保留了其角动量,并且下降到中心的气体具有很强的中心质量浓度。高斯-赫尔米特矩h 3和h 4有效地参数化了与高斯性的偏差,这与LOSVD的偏度和峰度有关。我们使用Gadget-2模拟,包括恒星形成,辐射冷却和来自的反馈,量化了(h 3,h 4)-v /σ关系对1:1合并中祖盘初始气体分数f gas的依赖性。超新星和活跃的银河核。对于f气体15%,h 3和v /σ之间的整体相关性很弱,它由从侧面观察角度产生的平坦负相关分量以及从更多面对上投影引起的陡峭正相关部分组成。随着f气体从0%增加到15%,v /σ值的分布向高正h 4减小,并且趋向于向h 4更低。对于f气体20%,(h 3,h 4)-v /σ分布看起来很不一样-存在紧密的h 3-v /σ负相关性,并且在所有h 4时,v /σ值分布较广与观察结果更好地吻合。高f气体残留物的重新合并(代表干合并)产生具有近高斯LOSVD的缓慢旋转的系统。我们根据残留物的潜在轨道结构解释了所有这些趋势,这是由它们的耗散形成历史所塑造的。

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