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arXiv 1001.1409astro-ph.COastro-ph.GA
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椭圆星系中射电喷流方向的二分法

A dichotomy in radio jet orientations in elliptical galaxies

I. W. A. Browne, R. A. Battye

摘要:

我们研究了14302个r星等大于18的SDSS星系的光学等照度线位置角和射电等照度线位置角之间的相关性。所有的星系都是由扩展的FIRST射电源确定的。对于被动早型星系,我们区分从其他使用的颜色,浓度和它们的主成分,我们发现一个强大的统计校准的射电轴与光学短轴。由于无线电发射是由吸积驱动的核黑洞,我们认为,所观察到的相关性提供了新的见解椭圆星系的结构,例如,是否从其余的星系的核运动学解耦。我们的研究结果意味着,一个显着的一部分星系是扁球体,也许旋转支持,与他们的无线电发射对准恒星短轴。值得注意的是,射电长轴与光学短轴的相关性的强度取决于射电响度。FIRST射电流量密度与恒星总光之比低的天体,短轴相关性强,而较强的射电源则不强。这种分裂可能反映了不同的形成历史,我们认为这可能是一个新的表现形式,更好地了解慢旋转和快速旋转的椭圆形之间的二分法。

英文摘要:

We have investigated the correlations between optical and radio isophotal position angles for 14302 SDSS galaxies with r magnitudes brighter than 18. All the galaxies are identified with extended FIRST radio sources. For passive early-type galaxies, which we distinguish from the others by using the colour, concentration and their principal components, we find a strong statistical alignment of the radio axes with the optical minor axes. Since the radio emission is driven by accretion on to a nuclear black hole we argue that the observed correlation gives new insight into the structure of elliptical galaxies, for example, whether or not the nuclear kinematics are decoupled from the rest of the galaxy. Our results imply that a significant fraction of the galaxies are oblate spheroids, perhaps rotationally supported, with their radio emission aligned with the stellar minor axis. Remarkably, the strength of the correlation of the radio major axis with the optical minor axis depends on radio loudness. Those objects with a low ratio of FIRST radio flux density to total stellar light show a strong minor axis correlation while the stronger radio sources do not. This split may reflect different formation histories and we suggest this may be a new manifestation of the better known dichotomy between slow rotating and fast rotating ellipticals.

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