追踪M81中的螺旋密度波
Tracing spiral density waves in M81
摘要：
我们使用斯皮策IRAC 3.6和4.5微米的近红外数据从斯皮策红外附近星系巡天（SINGS），光学B，V和I和2 MASS Ks波段数据产生的质量表面密度图的M81。IRAC的3.6和4.5微米数据，虽然占主导地位的老恒星星族的排放，是由年轻的恒星和PAH排放的小规模污染校正。I波段数据被用来产生一个质量表面密度图的B-V颜色校正，贝尔和德容的方法。我们将每个质量图拟合一个凸起和指数圆盘，并减去这些分量以揭示非轴对称质量表面密度。从剩余的质量地图，我们能够提取的振幅和相位的密度波，使用方位角配置文件。气体的响应是通过在8微米IRAC波段的尘埃排放来观察的，这使得恒星密度波和气体冲击的相位之间可以进行比较。这个角度偏移和半径之间的关系表明，螺旋结构是相当长的寿命，并允许共转的位置被确定。
英文摘要：
We use SPITZER IRAC 3.6 and 4.5micron near infrared data from the Spitzer Infrared Nearby Galaxies Survey (SINGS), optical B, V and I and 2MASS Ks band data to produce mass surface density maps of M81. The IRAC 3.6 and 4.5micron data, whilst dominated by emission from old stellar populations, is corrected for small-scale contamination by young stars and PAH emission. The I band data are used to produce a mass surface density map by a B-V colour-correction, following the method of Bell and de Jong. We fit a bulge and exponential disc to each mass map, and subtract these components to reveal the non-axisymmetric mass surface density. From the residual mass maps we are able to extract the amplitude and phase of the density wave, using azimuthal profiles. The response of the gas is observed via dust emission in the 8micron IRAC band, allowing a comparison between the phase of the stellar density wave and gas shock. The relationship between this angular offset and radius suggests that the spiral structure is reasonably long lived and allows the position of corotation to be determined.
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