视环状星系SDSS J075234 .33+292049.8的性质
On the Nature of the Apparent Ring Galaxy SDSS J075234.33+292049.8
摘要：
一个在联机数据库中被归类为星系并在巡天图像上显示为遥远的环星系的物体是极环星系的一个罕见情况，其环仅略微倾斜于中心体的赤道平面。SDSS成像显示，环的直径约为36千秒差距。SDSS数据与长缝分光观测和俄罗斯科学院6米望远镜获得的法布里-珀罗干涉仪H-β测绘相结合。我们得出了复杂的形态，这个假定的环星系的SDSS图像的组合，并从中心体和环的运动学行为，并确定了恒星星族组成的两个组件SDSS的颜色，光谱和演化恒星合成模型。环金属丰度略低于丰度。该系统的总光度和总质量并不极端，但相当高的M/L~（20）表明存在大量的暗物质。提出了该目的的两种替代解释：（1）由在中心杆的端部处的两个半圆形且紧密的螺旋臂形成的环，环材料具有翘曲或旋进。因此，这个天体可以被解释为一个极端的SBa（R）星系，或者（2）一个极环星系，其中内部的天体是一个S 0，环比中心的天体要亮得多。这个复合天体与NGC 4650 A星系类似，是一个极区成分仅略微倾斜于中心天体赤道面的罕见天体。支持（和反对）这两种解释的论点给出和讨论，与第二种选择更容易接受。
英文摘要：
(abridged) An object classified as a galaxy in on-line data bases and revealed on sky survey images as a distant ring galaxy is a rare case of polar ring galaxy where the ring is only slightly inclined to the equatorial plane of the central body. SDSS imaging indicates that the diameter of the ring is about 36 kpc. The SDSS data was combined with long-slit spectroscopic observations and with Fabry-Perot Interferometer H-beta mapping obtained at the Russian Academy of Sciences 6-m telescope. We derived the complex morphologies of this presumed ring galaxy from a combination of SDSS images and from the kinematical behaviour of the central body and of the ring, and determined the stellar population compositions of the two components from SDSS colours, spectroscopy, and evolutionary stellar synthesis models. The ring metallicity is slightly under-abundant. The total luminosity and the total mass of the system are not extreme, but the rather high M/L~20 indicates the presence of large amounts of dark matter. Two alternative explanations of this object are proposed (1) a ring formed by two semi-circular and tight spiral arms at the end of a central bar with a warp or precession of the ring material. The object could, therefore, be explained as an extreme SBa(R) galaxy, or (2) a Polar Ring Galaxy where the inner object is an S0 and the ring is significantly more luminous than the central object. The compound object would then be similar to the NGC 4650A galaxy, being a rare object with a polar component only modestly inclined to the equatorial plane of the central body. Arguments for (and against) both explanations are given and discussed, with the second alternative being more acceptable.
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