科研之友
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摘要
A study is presented of H i line observations of the nearby spiral galaxy NGC 3521 observed with the Very Large Array as part of The H i Nearby Galaxy Survey. Clearly evident in the H i data cube is the presence of an anomalous H i component that is both diffuse and slow rotating. The data cube is dynamically decomposed into regular and anomalous H i components. A mass of MH1 = 1.5 x 10(9) M-circle dot is estimated for the anomalous H i - 20 per cent of the total H i mass. Standard H i data products and rotation curves are produced for each dynamical component. In terms of circular rotation speed, the anomalous H i is found to lag the regular H i by similar to 25-125 km s(-1). Three-dimensional models are generated and used to determine the possible location of the anomalous H i. The results strongly suggest it to be distributed in a thick disc with a scale-height of a few kpc (similar to 3.5 kpc). It is concluded that the anomalous H i in NGC 3521 constitutes a slow-rotating halo gas component, consistent with similar findings for other nearby galaxies. A study of the radial distribution of the anomalous H i shows it to be spatially coincident with the inner regions of the stellar disc where the star formation rate is highest. It is most likely a galactic fountain that has deposited gas from the disc of the galaxy into the halo.
- 出版日期2014-2
