An Optical and H I Study of NGC 5850: Victim of a High-Speed Encounter?
An Optical and H I Study of NGC 5850: Victim of a High-Speed Encounter?
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NGC 5850 的光学和 H I 研究：高速相遇的受害者？
DOI：
10.1086/300193
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
G. Purcell
中科院分区：
文献类型：
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作者：
J. Higdon;R. Buta;G. Purcell
我们目前的光学CCD表面测光和VLA H I观测的NGC 5850，最大和最明亮的棒旋的内环品种在天空中。宽带图像揭示了许多形态学的特点，特别是在旋臂。结构不对称性在H I中更为明显，最明显的是大规模的气体向核的西部和西北部位移。（3.3 ± 0.1）× 109 M的氢原子主要集中在突出的光环和微弱的旋臂中，在凸起和旋臂间区域氢表面密度（H_2H_I）很低.我们在核环的西南半部分检测到大约2 × 107 M的H I。旋臂外的H I表面密度迅速下降，我们没有发现大尺度潮汐特征或大于0.05 M Tpc-2（3 σ）的扩展气盘的证据。总的来说，强度加权的H I速度场看起来相当规则，但仍然显示出明显的偏离圆形旋转，我们归因于一个扭曲的椭圆形盘和跨臂的流运动。在20厘米处的射电连续辐射主要是由一个微弱的凸起部分，峰值在光学核。未检测到旋臂。在整个NGC 5846星系群中没有X射线辐射，而NGC 5850的光学和H I形态非常相似，这表明该星系特殊形态的原因是由于致密的星系际介质的冲压压力剥离。我们将其归因于与大质量椭圆星系NGC 5846的高速相遇。我们确定了一个被破坏的外部伪环的特殊的旋臂。NGC 5850中的星星形成相对于其他中间场螺旋并没有增强，也没有大量的气体被输送到核中。这可能归因于最近（约2亿年）相互作用的性质。
We present optical CCD surface photometry and VLA H I observations of NGC 5850, one of the largest and brightest barred spirals of the inner ring variety in the sky. The broadband images reveal numerous morphological peculiarities, particularly in the spiral arms. Structural asymmetries are more obvious in H I, the most pronounced being a large-scale displacement of gas to the west and northwest of the nucleus. Most of the (3.3 ± 0.1) × 109 M☉ of atomic hydrogen is concentrated in the prominent optical ring and faint spiral arms, with very low H I surface densities (ΣH I) in the bulge and interarm regions. We detect approximately 2 × 107 M☉ of H I in the southwestern half of the nuclear ring. The H I surface density drops rapidly outside the arms, and we find no evidence for either large-scale tidal features or an extended gas disk above 0.05 M☉ pc-2 (3 σ). Overall, the intensity-weighted H I velocity field appears fairly regular, yet still shows clear deviations from circular rotation that we attribute to a warped oval disk and streaming motions across the arms. Radio continuum emission at 20 cm is dominated by a faint bulge component that peaks at the optical nucleus. The spiral arms are not detected. The absence of extended X-ray emission throughout the NGC 5846 group and the close similarity between NGC 5850's optical and H I morphologies argue against ram pressure stripping through a dense intergalactic medium as the cause of the galaxy's peculiar morphology. We attribute it instead to a high-speed encounter with the massive elliptical galaxy NGC 5846. We identify the peculiar spiral arms as a disrupted outer pseudoring. Star formation in NGC 5850 has not been enhanced relative to other intermediate field spirals, nor have significant gas masses been transported to the nucleus. This may be attributed to the recent (≲200 Myr) nature of the interaction.