标题： 超新星反馈维持附近恒星形成星系气体湍流的证据 显示英文标题

标题： Evidence for supernova feedback sustaining gas turbulence in nearby star-forming galaxies

摘要： 众所周知，星系盘中的气体具有高度湍动性，但关于何种机制能够在能量上维持这种湍动性仍存在许多争议。 在可能的候选机制中，超新星（SN）爆发被认为是主要驱动力，但在恒星形成活动适度的区域，尤其是盘的外缘，是否足够仍存疑。 本文中，我们测量了超新星效率 $\eta$，即维持星系湍动所需的总超新星能量的比例，并验证了超新星确实可以成为唯一的驱动机制。 我们方法的关键创新之处在于考虑了气盘外缘膨胀引起的湍动耗散时间尺度的增加。 我们分析了10个附近恒星形成星系中的HI和CO分布及其运动学特性，以获得原子气体和分子气体单位面积动能的径向分布。 我们使用一个理论模型，利用从观测到的恒星形成率（SFR）面密度推断出的超新星湍动能以及气体热能之和来重现观测到的能量。 我们发现，在整个星系盘范围内，假设 $\eta$ 随星系中心半径保持恒定的情况下，我们的模型能够非常出色地再现观测到的动能。 考虑到恒星形成率面密度和原子气体相位的不确定性，我们得出样本星系的中值超新星效率分别为 $\langle \eta_\mathrm{atom} \rangle=0.015_{-0.008}^{+0.018}$ 对于原子气体和 $\langle \eta_\mathrm{mol} \rangle = 0.003_{-0.002}^{+0.006}$ 对于分子气体。 我们得出结论，超新星仅需它们能量的百分之几就可以维持附近星系中的气体湍动，且基本上不需要任何进一步的能量来源。 显示英文摘要

摘要： It is well known that gas in galaxy discs is highly turbulent, but there is much debate on which mechanism can energetically maintain this turbulence. Among the possible candidates, supernova (SN) explosions are likely the primary drivers but doubts remain on whether they can be sufficient in regions of moderate star formation activity, in particular in the outer parts of discs. In this paper, we measure the SN efficiency $\eta$, namely the fraction of the total SN energy needed to sustain turbulence in galaxies, and verify that SNe can indeed be the sole driving mechanism. The key novelty of our approach is that we take into account the increased turbulence dissipation timescale associated to the flaring in outer regions of gaseous discs. We analyse the distribution and kinematics of HI and CO in 10 nearby star-forming galaxies to obtain the radial profiles of the kinetic energy per unit area, for both the atomic gas and the molecular gas. We use a theoretical model to reproduce the observed energy with the sum of turbulent energy from SNe, as inferred from the observed star formation rate (SFR) surface density, and the gas thermal energy. We find that the observed kinetic energy is remarkably well reproduced by our model across the whole extent of the galactic discs, assuming $\eta$ constant with the galactocentric radius. Taking into account the uncertainties on the SFR surface density and on the atomic gas phase, we obtain that the median SN efficiencies for our sample of galaxies are $\langle \eta_\mathrm{atom} \rangle=0.015_{-0.008}^{+0.018}$ for the atomic gas and $\langle \eta_\mathrm{mol} \rangle = 0.003_{-0.002}^{+0.006}$ for the molecular gas. We conclude that SNe alone can sustain gas turbulence in nearby galaxies with only few percent of their energy and that there is essentially no need for any further source of energy.