重力加热有助于使大量的Galerkin变红和死亡
Gravitational Heating Helps Make Massive Galaxies Red and Dead
摘要：
我们研究了四个模拟星系的热形成历史，这些星系在Naab等人（2007）中被展示出来，以再现椭圆星系的一些观测特性。星系中气体的温度随着红移的减小而稳步上升，尽管大部分气体的冷却时间比哈勃时间短。气体被重力加热过程加热并保持高温，这是通过从下落的恒星团释放势能来实现的。能量在下落的气体块与周围气体的超音速碰撞中以及通过卫星系统的动态捕获而耗散，从而引起将能量转移到周围气体的重力尾流。此外，下落的团块产生的动力学摩擦将暗物质挤出，使中心的暗物质密度从z=3到z=0降低了2倍。在星系的晚期形成历史（z<2）中，即使在没有超新星和活动星系核反馈的情况下，引力反馈释放的能量（E~ 5 × 10 ^{59}尔格）也足以在z~1形成红色和死亡的椭圆星系。
英文摘要：
We study the thermal formation history of four simulated galaxies that were shown in Naab et al. (2007) to reproduce a number of observed properties of elliptical galaxies. The temperature of the gas in the galaxies is steadily increasing with decreasing redshift, although much of the gas has a cooling time shorter than the Hubble time. The gas is being heated and kept hot by gravitational heating processes through the release of potential energy from infalling stellar clumps. The energy is dissipated in supersonic collisions of infalling gas lumps with the ambient gas and through the dynamical capturing of satellite systems causing gravitational wakes that transfer energy to the surrounding gas. Furthermore dynamical friction from the infalling clumps pushes out dark matter, lowering the central dark matter density by up to a factor of two from z=3 to z=0. In galaxies in which the late formation history (z<2) is dominated by minor merging and accretion the energy released (E~5x10^{59} ergs) from gravitational feedback is sufficient to form red and dead elliptical galaxies by z~1 even in the absence of supernova and AGN feedback.
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