Modeling Nearly Spherical Pure-bulge Galaxies with a Stellar Mass-to-light Ratio Gradient under the ΛCDM and MOND Paradigms. II. The Orbital Anisotropy of Slow Rotators within the Effective Radius
Modeling Nearly Spherical Pure-bulge Galaxies with a Stellar Mass-to-light Ratio Gradient under the ΛCDM and MOND Paradigms. II. The Orbital Anisotropy of Slow Rotators within the Effective Radius
复制标题
DOI：
10.3847/1538-4357/ab09fd
复制
发表时间：
2019-02
期刊：
影响因子：
--
通讯作者：
K. Chae;M. Bernardi;R. Sheth
中科院分区：
文献类型：
--
作者：
K. Chae;M. Bernardi;R. Sheth
本文研究了24个纯球星系中恒星速度色散在有效半径Re内的各向异性，其中16个是运动学慢旋星系。我们允许球面各向异性参数β径向变化，并允许通过前面介绍的参数K在恒星质光比（M/L）中存在径向梯度。SR的中值各向异性取决于K如下：a = 0.19 ± 0.05，B = −0.13 ± 0.07（ΛCDM）或a = 0.21 ± 0.05，B = −0.26 ± 0.08（MOND），其中βm是指径向平均量。在ΛCDM范式下，这种缩放与的缩放有关，其中fDM是指在r = Re的球体内的暗物质（DM）分数。对于K = 0（常数M/L），我们得到了径向有偏的结果，与以前的结果一致.然而，边缘化超过0 < K < 1.5产生各向同性是优选的。这种各向同性隐藏了βm与运动学特征相关的事实，例如反向旋转核心（CRC），运动学上不同的核心（KDC）和低层速度（LV）;具有LV的SR可能是径向偏置的，而具有CRC的SR可能是切向偏置的，而具有KDC的SR是中间的。现有的宇宙学模拟使我们能够从动力学结构和形成历史的角度定性地理解这些结果，尽管存在定量的紧张关系。更现实的宇宙学模拟，特别是考虑到M/L梯度，可能需要更好地理解SR。
We investigate the anisotropy of the stellar velocity dispersions within the effective radius, Re, in 24 pure-bulge galaxies, 16 of which are kinematic slow rotators (SRs). We allow the spherical anisotropy parameter β to be radially varying and allow a radial gradient in the stellar mass-to-light ratio (M⋆/L) through the parameter K introduced earlier. The median anisotropy for SRs depends on K as follows: with a = 0.19 ± 0.05, b = −0.13 ± 0.07 (ΛCDM) or a = 0.21 ± 0.05, b = −0.26 ± 0.08 (MOND), where βm refers to the radially averaged quantity. Under the ΛCDM paradigm, this scaling is tied to a scaling of , where fDM refers to the dark matter (DM) fraction within a sphere of r = Re. For K = 0 (constant M⋆/L), we obtain radially biased results with , consistent with previous results. However, marginalizing over 0 < K < 1.5 yields with ; isotropy is preferred. This isotropy hides the fact that βm is correlated with kinematic features such as counterrotating cores (CRCs), kinematically distinct cores (KDCs), and low-level velocities (LVs); SRs with LVs are likely to be radially biased, while SRs with CRCs are likely to be tangentially biased, and SRs with KDCs are intermediate. Existing cosmological simulations allow us to understand these results qualitatively in terms of their dynamical structures and formation histories, although there are quantitative tensions. More realistic cosmological simulations, particularly allowing for M⋆/L gradients, may be required to better understand SRs.