arXiv 1707.080852017-07-25astro-ph.GA

低表面亮度星系起源的动力学研究

Origin of low surface brightness galaxies: A dynamical study

Prerak Garg, Arunima Banerjee

备注：: 9 pages, 6 figures, 2 tables (Accepted for publication in the MNRAS)
DOI：: 10.1093/mnras/stx1918

摘要：

低表面亮度星系（LSB），尽管富含气体，但恒星形成率低，因此在自然界中表面亮度低。我们计算了Q $_{\rm{RW}}$，这是Romeo \& Wiegert（2011）提出的2分量盘稳定性参数，作为5个LSB样本的银河中心半径$R$的函数，其质量模型可从HI 21 cm放射性合成观测和R-波段光度测量中获得。我们发现，对于我们的样本LSB，Q $_{\rm{RW}}^{\rm{min}}$的中值，即Q $_{\rm{RW}}$在$R$上的最小值，在2.6和3.1之间，这高于早期研究中获得的高表面亮度星系（HSB）样本的Q $_{\rm{RW}}^{\rm{min}}$的中值1.8 $\pm$ 0.3。这清楚地表明，LSB比HSB具有更稳定的圆盘，这可以解释它们的低恒星形成率，以及可能的低表面亮度性质。有趣的是，如果盘只对暗物质晕的引力势作出反应，Q $_{\rm{RW}}$的计算值只会略微降低（Q $_{\rm{RW}}^{\rm{min}}$ $\sim$的中值为2.3 - 3），但如果盘只对自身引力作出反应，则$\sim$会降低2-3倍（Q $_{\rm{RW}}^{\rm{min}}$ $\sim$的中值为0.7 - 1.5）。这意味着暗物质晕在调节LSB中的盘稳定性方面至关重要，这可能对星系形成和演化的模型具有重要意义。

英文摘要：

Low Surface Brighness Galaxies (LSBs), inspite of being gas rich, have low star formation rates and are, therefore, low surface brightness in nature. We calculate Q$_{\rm{RW}}$, the 2-component disc stability parameter as proposed by Romeo \& Wiegert (2011), as a function of galactocentric radius $R$ for a sample of five LSBs, for which mass models, as obtained from HI 21cm radio-sythesis observations and R-band photometry, were available in the literature. We find that the median value of Q$_{\rm{RW}}^{\rm{min}}$, the minimum of Q$_{\rm{RW}}$ over $R$, lies between 2.6 and 3.1 for our sample LSBs, which is higher than the median value of 1.8 $\pm$ 0.3 for Q$_{\rm{RW}}^{\rm{min}}$ for a sampleof high surface brightness galaxies (HSBs) as obtained in earlier studies. This clearly shows that LSBs have more stable discs than HSBs, which could explain their low star formation rates and, possibly, their low surface brightness nature. Interestingly, the calculated values of Q$_{\rm{RW}}$ decrease only slightly (median Q$_{\rm{RW}}^{\rm{min}}$ $\sim$ 2.3 - 3) if the discs were taken to respond to the gravitational potential of the dark matter halo only, but reduce by $\sim$ a factor of 2-3 (median Q$_{\rm{RW}}^{\rm{min}}$ $\sim$ 0.7 - 1.5) if they respond to their self-gravity alone. This implies that the dark matter halo is crucial in regulating disc stability in LSBs, which may have important implications for models of galaxy formation and evolution.

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