We present results from high--resolution cosmological hydrodynamical simulations of a Milky--Way-sized halo, aimed at studying the effect of feedback on the nature of gas accretion. Simulations include a model of inter-stellar medium and star formation, in which SN explosions provide effective thermal feedback. We distinguish between gas accretion onto the halo, which occurs when gas particles cross the halo virial radius, and gas accretion onto the central galaxy, which takes place when gas particles cross the inner one-tenth of the virial radius. Gas particles can be accreted through three different channels, depending on the maximum temperature value, $T_{\rm max}$, reached during the particles' past evolution: a cold channel for $T_{\rm max}<2.5 \times 10^5$ K, a hot one for $T>10^6$K, and a warm one for intermediate values of $T_{\rm max}$. We find that the warm channel is at least as important as the cold one for gas accretion onto the central galaxy. This result is at variance with previous findings that the cold mode dominates gas accretion at high redshift. We ascribe this difference to the different supernova feedback scheme implemented in our simulations. While results presented so far in the literature are based on uneffective SN thermal feedback schemes and/or the presence of a kinetic feedback, our simulations include only effective thermal feedback. We argue that observational detections of a warm accretion mode in the high--redshift circum-galactic medium would provide useful constraints on the nature of the feedback that regulates star formation in galaxies.
A Correlation between Star Formation Rate and Average Black Hole Accretion in Star-forming Galaxies (Proceeding of IAUS304: Multiwavelength AGN Surveys and Studies)
The bending of the star-forming main sequence traces the cold- to hot-accretion transition mass over 0<z<4
我们分析了恒星质量（M0）的变化，在那里恒星形成的主序列（MS）的弯曲发生在0<z<4。我们发现在0<z<1时M0~10^10Msun，然后在z=2时M0上升到~10^11Msun，然后保持平稳或向更高的红移缓慢增加。当转换成托管暗物质晕质量的M0值，我们表明，这种行为是非常一致的不断发展的冷到热吸积过渡质量，理论预测和定义的红移无关的Mshock在z <1.4 and by the rising Mstream at z>1.4（我们提出了一个修订与最新的模拟协议）。因此，我们认为MS弯曲主要是由于冷吸积的减少导致星系中可用冷气体的减少，并支持气体馈送理论的预测。特别是，在z>1处红移的快速上升的M0证实了冷流情景的证据。在这幅图中，在质量大于M0的星系中，逐渐减少燃料而不是突然抑制质量大于Mshock/Mstream的晕，会产生几乎恒定的恒星形成速率，而不是它们的淬灭，因此需要其他物理过程。与星系恒星质量函数中的膝盖M* 相比，M0在z<1.5时显着较低，在z>2时较高，这表明气体匮乏对星系质量分布的影响发生在早期（z>1.5-2）。MS内部星系成为膨胀主导的典型质量与M0的演变不同，这与膨胀形成是一个与冷吸积逐渐消失不同的过程的想法一致。
