标题： 浅暗物质密度分布盘状矮星系的潮汐搅拌：向矮椭圆星系的转化增强 显示英文标题

标题： Tidal Stirring of Disky Dwarfs with Shallow Dark Matter Density Profiles: Enhanced Transformation into Dwarf Spheroidals

摘要： （精简版）本星系群（LG）矮椭球星系（dSphs）的起源仍然是一个谜。 潮汐搅拌模型提出，类似现今矮漩涡星系（dIrr）的晚期旋转型矮星系可以通过与银河系大小的宿主星系相互作用而转变为dSphs。 利用无碰撞N体模拟，我们首次研究了潮汐搅拌如何依赖于祖先盘状矮星系中心恒星区域内的暗物质（DM）密度分布。 具体来说，我们探索了矮星系DM密度剖面的各种渐近内坡度gamma（rho \propto r^{-γ} 当r -> 0时）。 对于给定的主轨道内，嵌入核心状密度分布（gamma = 0.2）和温和密度尖峰（gamma = 0.6）的暗物质晕中的旋转支持矮星系，其转化为dSphs的可能性和效率显著高于具有更陡峭DM密度剖面（gamma = 1）的对应物。 这种浅层DM分布类似于观测到的dIrrs，强调了潮汐搅拌作为本星系群形态-密度关系的合理模型。 当gamma <1时，单次近日点经过可以诱导dSph形成，并且低偏心率或大近日点距离轨道上的盘状矮星系能够转化为dSphs；这些新结果使潮汐搅拌模型能够解释几乎所有的已知dSphs，无论它们距离宿主星系有多远。 一部分gamma <1的旋转支持矮星系最终被主星系破坏；那些幸存下来的dSphs通常轨道偏心率较低和/或近日点距离较大，相对于典型的冷暗物质（CDM）卫星轨道而言。 后者可能解释了一些经典本星系群dSphs（如Fornax、Leo I、Tucana和Cetus）相当奇特的轨道。 显示英文摘要

摘要： (Abridged) The origin of dSphs in the Local Group (LG) remains an enigma. The tidal stirring model posits that late-type, rotationally-supported dwarfs resembling present-day dwarf irregular (dIrr) galaxies can transform into dSphs via interactions with Milky Way-sized hosts. Using collisionless N-body simulations, we investigate for the first time how tidal stirring depends on the dark matter (DM) density distribution in the central stellar region of the progenitor disky dwarf. Specifically, we explore various asymptotic inner slopes gamma of the dwarf DM density profiles (rho \propto r^{-gamma} as r -> 0). For a given orbit inside the primary, rotationally-supported dwarfs embedded in DM halos with core-like density distributions (gamma = 0.2) and mild density cusps (gamma = 0.6) demonstrate a substantially enhanced likelihood and efficiency of transformation into dSphs compared to their counterparts with steeper DM density profiles (gamma = 1). Such shallow DM distributions are akin to those of observed dIrrs, highlighting tidal stirring as a plausible model for the LG morphology-density relation. When gamma <1, a single pericentric passage can induce dSph formation and disky dwarfs on low-eccentricity or large-pericenter orbits are able to transform into dSphs; these new results allow the tidal stirring model to explain the existence of virtually all known dSphs across a wide range of distances from their hosts. A subset of rotationally-supported dwarfs with gamma <1 are eventually disrupted by the primary; those that survive as dSphs are generally on orbits that are biased towards lower eccentricities and/or larger pericenters relative to those of typical CDM satellites. The latter could explain the rather peculiar orbits of several classic LG dSphs such as Fornax, Leo I, Tucana, and Cetus.