棒对旋涡星系中央恒星形成的作用

The Effects of Bar Sturcture on the Central sSFR of Spiral Galaxies

使用了目前最大的棒旋星系样本之一,着重于研究旋涡星系中央的比恒星形成率(sSFR)和棒结构的关系。我们用1g sSFR=-11 a^(-1)作为星系宁静态和活跃态的分界,统计对比了棒旋星系和非棒旋星系中央的sSFR,发现相对于非棒旋星系,棒旋星系处于中央宁静态的比重更大,而在中央活跃态其恒星形成活动更剧烈。为消除星系样本恒星质量差异对星系中央sSFR统计结果的影响,获得控制样本,使棒旋星系和非棒旋星系具有相同的恒星质量分布。随后发现这两类星系在中央宁静态中的统计差异消失,而在中央活跃态棒旋星系的恒星形成活动依旧相对剧烈,尤其体现在长棒星系中。这说明棒结构对旋涡星系中央的恒星形成起到促进作用,且作用效果与棒的长短相关。

We investigate the effects of bars in spiral galaxies on galaxy central specific Star Formation Rate （sSFR） using a sample of over 9000 spiral galaxies drawn from Sloan Digital Sky Survey, with morphological classifications assigned by visual inspection. Our sample includes three types： none-barred galaxies and galaxies hosting long or short bars, respectively. By identifying star-forming and quiescent population, we find barred spiral galaxies tend to be central quiescent. However, the star-forming barred spiral galaxies tend to have stronger central star forming activities than the unbarred spiral galaxies. In order to find the connection between central sSFR and the presence of a bar within the spiral galaxy, we construct control samples where barred and unbarred ones are closely matched by stellar mass. We then find the same proportion of central quiescent galaxies for barred and unbarred ones. Furthermore, the star-forming barred ones still have stronger central star forming activities than the unbarred ones with the signal mainly coming from the long barred ones. These results demonstrate that bars may have no influence on central star quiescence, but bars can induce the central star formation in their host spiral galaxies where the effect are mainly contributed by long bars.