暗物质主导星系中的慢棒
A slow bar in a dark matter dominated galaxy
摘要：
我们报告的低表面亮度的螺旋星系UGC 628的条形图案的速度欧米茄_p的估计。我们应用Tüve-Weinberg方法的高分辨率Halalpha速度和集成的发射图，这个暗物质占主导地位的星系。在CFHT使用光学法布里-珀罗干涉仪（FaNTOmM）进行观测。Tüssee-Weinberg方法估计UGC 628的条形图速度为（11.3 +/- 2.0）km/s/kpc，这是螺旋星系中最低的速度。棒和气体盘的共转半径Rc = 9.8（+2.9/-2.0）kpc，意味着R = Rc/Ab = 2.0（+0.5/-0.3），其中Ab是棒的半径。这个比值远远超出了通常的数值范围，即1.0< R <1.4，这是在高表面亮度棒星系的快棒中发现的。这意味着UGC 628中的酒吧很慢。通过数值模拟表明，当星系内部的质量分布由暗物质上的重子主导时，快棒仍然存在。我们的结果表明，星系中慢棒的存在可能与暗物质在质量分布中的主导地位有关。
英文摘要：
We report on an estimate of the bar pattern speed Omega_p for the low surface brightness spiral galaxy UGC 628. We applied the Tremaine-Weinberg method to high resolution Halpha velocity and integrated emission maps of this dark matter dominated galaxy. Observations were made at the CFHT using the optical Fabry-Perot interferometer, FaNTOmM. The Tremaine-Weinberg method estimates a bar pattern speed of (11.3 +/- 2.0) km/s/kpc for UGC 628, which is among the lowest values found for a spiral galaxy. The corotation radius Rc of the bar and the gaseous disc is Rc = 9.8 (+2.9/-2.0) kpc, implying a ratio R = Rc/Ab of 2.0 (+0.5/-0.3), where Ab is the bar radius. The ratio is well beyond the usual range of values, 1.0< R <1.4, found for fast bars of high surface brightness barred galaxies. It implies that the bar in UGC 628 is slow. As shown through the use of numerical simulations, fast bars survive when the inner mass distribution of galaxies is dominated by the baryons over the dark matter. Our result suggests that the presence of slow bars in galaxies is likely related to the dominance of dark matter over the mass distribution.
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