NGC 1569是一个附近的矮不规则星系,在1000万年到4000万年前经历了一次强烈的恒星形成爆发。我们目前的意见,达到表面亮度比以前的无线电连续观测和第一无线电连续极化观测微弱2至80倍。这些观测使我们能够探测NGC 1569的磁场与其其余星际介质的关系。我们确认存在一个扩展的无线电连续晕在20厘米,并看到第一次的无线电连续功能与西方Halalpha臂在波长短于20厘米。这个星系的光谱指数趋势支持这个星系中有对流风的理论。我们得出的总磁场强度的38 microG的中心区域和10-15 microG的晕。星系中心的磁场很大程度上是随机的;均匀磁场约为3-9 microG,在晕中最强。我们发现,磁压力是相同的数量级,但在一般情况下,一个小的因素比其他组成部分的星际介质在这个星系。NGC 1569中的均匀磁场与H α泡和细丝密切相关。我们认为,一个超新星驱动的发电机可能在这个星系中运行。从NGC 1569流出的热气体显然塑造了磁场,但磁场反过来可能通过将气体引导出星系盘来帮助流出。像NGC 1569这样具有扩展射电连续晕的矮星系可能在磁化星系际介质中发挥重要作用。
英文摘要:
(abridged) NGC 1569 is a nearby dwarf irregular galaxy which underwent an intense burst of star formation 10 to 40 Myr ago. We present observations that reach surface brightnesses two to eighty times fainter than previous radio continuum observations and the first radio continuum polarization observations. These observations allow us to probe the relationship of the magnetic field of NGC 1569 to the rest of its interstellar medium. We confirm the presence of an extended radio continuum halo at 20 cm and see for the first time the radio continuum feature associated with the western Halpha arm at wavelengths shorter than 20cm. The spectral index trends in this galaxy support the theory that there is a convective wind at work in this galaxy. We derive a total magnetic field strength of 38 microG in the central regions and 10-15 microG in the halo. The magnetic field is largely random in the center of the galaxy; the uniform field is ~3-9 microG and is strongest in the halo. We find that the magnetic pressure is the same order of magnitude but, in general, a factor of a few less than the other components of the interstellar medium in this galaxy. The uniform magnetic field in NGC 1569 is closely associated with the Halpha bubbles and filaments. We suggest that a supernova-driven dynamo may be operating in this galaxy. The outflow of hot gas from NGC 1569 is clearly shaping the magnetic field, but the magnetic field in turn may be aiding the outflow by channeling gas out of the disk of the galaxy. Dwarf galaxies with extended radio continuum halos like that of NGC 1569 may play an important role in magnetizing the intergalactic medium.
We present new observations with the Atacama Large Millimeter/sub-millimeter Array of the 122um and 205um fine-structure line emission of singly-ionised nitrogen in a strongly lensed starburst galaxy at z=2.6. The 122/205um [NII] line ratio is sensitive to electron density, n_e, in the ionised interstellar medium, and we use this to measure n_e~300cm^-3 averaged across the galaxy. This is over an order of magnitude higher than the Milky Way average, but comparable to localised Galactic star-forming regions. Combined with observations of the atomic carbon (CI(1-0)) and carbon monoxide (CO(4-3))…
Studying the interstellar medium of HII/BCD galaxies using IFU spectroscopy
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