The Impact of Star Formation on the Interstellar Medium in Dwarf Galaxies. II. The Formation of Galactic Winds
The Impact of Star Formation on the Interstellar Medium in Dwarf Galaxies. II. The Formation of Galactic Winds
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恒星形成对矮星系星际介质的影响。
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
C. Martin
中科院分区：
文献类型：
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作者：
C. Martin
14 个矮星系和 M82 的 Hα 发射图像和长缝中阶梯光栅光谱已被用来识别电离气体的膨胀壳层。在 12 个矮星中发现了超级壳（半径 >300 pc）。测量的壳尺寸和膨胀速度限制了气泡的寿命和功率需求。较大气泡的动态年龄通常约为 10 Myr，年龄超过 20 Myr 的电离壳很少见。在此期间，需要相当于 100-10,000 次超新星爆炸的能量来驱动扫出空腔的激波锋。目前的恒星形成率足以满足这些功率要求。许多炮弹将以超音速突破周围的 H I 层，但预计的膨胀速度通常小于逃逸速度的下限。一些壳层材料可能会永久地从NGC 1569等一些星系中逸出。无论是否与星系结合，这些流出物可能在调节恒星形成速率方面发挥着重要作用，并预计将显着影响星系的化学演化。这些壳以与当前银河系恒星形成速率相当甚至更高的速率将气体从盘中提起。只有当它们的工作周期比圆盘的旋转周期长得多时，它们才会取代大部分星际气体。
Images and long-slit echelle spectra of the Hα emission from 14 dwarf galaxies and M82 have been used to identify expanding shells of ionized gas. Supershells (radius >300 pc) are found in 12 of the dwarfs. The measured shell sizes and expansion speeds constrain the ages and power requirements of the bubbles. The dynamical age of the larger bubbles is typically about 10 Myr, and ionized shells older than 20 Myr are rare. An energy equivalent to 100-10,000 supernova explosions over this period is needed to drive the shock front that sweeps out the cavity. The current star formation rates are high enough to meet these power requirements. Many of the shells will break through the surrounding layer of H I supersonically, but the projected expansion speeds are typically less than the lower limits on the escape velocity. Some of the shell material may permanently escape from a few galaxies such as NGC 1569. Whether bound to the galaxy or not, these outflows probably play an important role in regulating the star formation rate and are expected to significantly influence the chemical evolution of the galaxies. The shells lift gas out of the disk at rates comparable to, or even greater than, the current galactic star formation rates. They will displace a substantial fraction of the interstellar gas only if their duty cycle is much longer than the rotational period of the disk.