Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy

摘要

SDSS J0905+57是一个红移值为0.7的小型大质量星爆星系，它在以对任何恒星形成星系来说已知最高的速度之一驱动着一股风。现在，在2毫米波段对这一星系所做的射电天文学观测显示，总分子气体的35%以高速度外流，延伸大约10"千秒差距"，其速度与来自恒星辐射压力的动量通量相一致。以前所知道的来自这种星系的外流延伸不到1"千秒差距"，并且只涉及总分子气体的一小部分。这一新发现表明，恒星形成的爆发过程能从一个星系的中心区域喷射出大量冷气体（用于恒星形成的原材料）,从而通过一个简单的反馈机制限制恒星质量的増长。%Recent observations have revealed that starburst galaxies can arive molecular gas outflows through stellar radiation pressure. Molecular gas is the phase of the interstellar medium from which stars form, so these outflows curtail stellar mass growth in galaxies. Previously known outflows, however, involve small fractions of the total molecular gas content and have typical scales of less than a kilopar-sec. In at least some cases, input from active galactic nuclei is dynamically important, so pure stellar feedback (the momentum return into the interstellar medium) has been considered incapable of rapidly terminating star formation on galactic scales. Molecular gas has been detected outside the galactic plane of the archetypal starburst galaxy M82 (refs 4 and 5), but so far there has been no evidence that star-bursts can propel substantial quantities of cold molecular gas to the same galactocentric radius (about 10 kiloparsecs) as the warmer gas that has been traced by metal ion absorbers in the circumgalactic medium. Here we report observations of molecular gas in a compact (effective radius 100 parsecs) massive starburst galaxy at red-shift 0.7, which is known to drive a fast outflow of ionized gas. We find that 35 per cent of the total molecular gas extends approximately 10 kiloparsecs, and one-third of this extended gas has a velocity of up to 1,000 kilometres per second. The kinetic energy associated with this high-velocity component is consistent with the momentum flux available from stellar radiation pressure. This demonstrates that nuclear bursts of star formation are capable of ejecting large amounts of cold gas from the central regions of galaxies, thereby strongly affecting their evolution by truncating star formation and redistributing matter.