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Hubble Space Telescope NICMOS Imaging of the Cores of M31 and M32

机译:哈勃太空望远镜NICMOS对M31和M32核的成像

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We present 1.1, 1.6, and 2.2 μm images of the cores of the Local Group galaxies M31 and M32 obtained with the Near Infrared Camera and Multi-Object Spectrometer of the Hubble Space Telescope (HST). These images are also compared with optical images of the galaxies obtained with the HST Wide Field Planetary Camera 2 (WFPC2). In M31, the nucleus remains distinctly asymmetric in all of the infrared bands, with no evidence of concentrated dust, although the distinction between the two nuclei, P1 and P2, is not as strong as in the WFPC2 and earlier WF/PC-1 images. This result is nonetheless consistent with the model of the nucleus as an eccentric stellar disk produced by the dynamical influence of a central supermassive black hole. Several individual M giant stars are detected within ~3'' of the nuclei and may represent stars that have escaped from the disk and phase-mixed around the nuclear center of mass. In M32 we also do not find strong evidence of dust, and the brightness profiles within the central ~1'' of the infrared images can be fitted by a power law of the same form as that fitted to the optical images. The infrared color profiles of the central few arcseconds of M32 show no strong gradients and indicate a population dominated by K giant stars. This is consistent with recent ground-based spectroscopy and photometry of the core region, which similarly show no strong gradients in age or metallicity within its stellar population.
机译:我们展示了用哈勃太空望远镜(HST)的近红外照相机和多目标光谱仪获得的本地群星系M31和M32核心的1.1、1.6和2.2μm图像。还将这些图像与使用HST广角行星相机2(WFPC2)获得的星系的光学图像进行比较。在M31中,尽管两个核P1和P2之间的区别不如WFPC2和早期WF / PC-1图像中的强,但在所有红外波段中,核仍明显不对称,没有尘埃集中的迹象。 。但是,这个结果与由中心超大质量黑洞的动力学影响产生的偏心恒星盘核模型是一致的。在原子核的〜3''范围内检测到了几颗M星,它们代表了从圆盘逸出并围绕核质心相混合的恒星。在M32中,我们也没有发现明显的灰尘迹象,并且红外图像中心〜1''内的亮度分布可以通过幂律来拟合,该幂律的形式与光学图像相同。 M32中心几弧秒的红外颜色轮廓没有显示出强烈的渐变,并指示了以K个巨星为主的种群。这与最近的核心区域的地面光谱学和光度学是一致的,后者在其恒星种群中同样没有显示出年龄或金属性的强烈梯度。

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