我們利用鹿林一米望遠鏡(LOT)拍攝了三個螺旋星系，M51、M83和M101的Hα影像；接著我們將這些影像和近紅外波段－2MASS的Ks影像做比較。這麼做的原因是為了要比較在星系的旋臂上，和旋臂間的空隙區域的Hα/K的比值。我們發現，在旋臂上，Hα/K的比值的確比在旋臂間的空隙區域來的高；由於Ks波段影像代表的是的星系中密度波的分佈，也就是說，在密度波分佈的區域，有較高的恆星形成率。另外，我們也發現了恆星形成區域(HII區域)大部分分佈在星系密度波分佈區域的前緣。上述兩個結果都暗示著，在我們所觀測的星系中，密度波是激發恆星形成的主要機制。 We have obtained Hαimages of three nearby face-on galaxies, M51, M83 and M101, by using the Lulin One-meter Telescope (LOT). We then compared these images to the near-infrared Ks band data which is obtained from the 2MASS catalog, in order to determine the Hα/K ratio of galaxies’ K-band arm regions and inter-arm regions. We have found that there is a significant enhancement of Hα/K ratio in K-band arm region, which refers to the location of the density wave. We have also found that the distribution of the HII regions locate on the leading edge of the K-band arms. Both evidences hint that the density wave is the dominant mechanism of star formation in these spiral galaxies, which is in agreement with the large-scale shock scenario, which predicts a high star formation efficiency in arm regions.
