Arp 147环星系系统的SWIFT观测
SWIFT Observations of the Arp 147 Ring galaxy system
摘要：
我们目前的观察Arp 147，一个星系系统，包括一个碰撞产生的环星系和一个早期型星系，使用牛津SWIFT积分场摄谱仪（IFS）在200英寸的黑尔望远镜。我们从IFS数据中获得空间分辨的运动学，并使用这些来研究两个星系之间的相互作用。我们发现环的边缘到边缘的膨胀速度是225 +/- 8 km/s，这意味着碰撞时间的上限为50百万年。我们还计算出碰撞的撞击角度在33度到54度之间，其中0度意味着垂直碰撞。环星系是强烈的恒星形成与恒星的形成可能已经触发了两个星系之间的碰撞。我们测量一些关键的物理参数，在一个综合的和空间分辨的方式为环星系。使用观察到的B-I颜色和H-α等效宽度，我们得出结论，两个恒星组件（一个年轻的和一个老的人口）需要同时匹配两个观察到的量。我们限制了环中年轻恒星形成的年龄范围，光和质量分数，发现一个适度的年龄范围，小于三分之一的光分数，和一个可以忽略不计的（<1%）质量分数。我们假设，在环星系东南角观察到的较红的颜色可能对应于形成环的原始盘星系的核凸起，与东南象限的恒星质量占总数的30-50%一致。这个环在遭遇之前似乎是一个典型的盘状星系。环显示的电子密度与恒星形成HII区域的典型值一致。环的东半部的金属丰度比西半部高出约2倍。在环上测量的电离参数大致遵循先前观察到的金属丰度趋势。
英文摘要：
We present observations of Arp 147, a galaxy system comprising a collisionally-created ring galaxy and an early-type galaxy, using the Oxford SWIFT integral field spectrograph (IFS) at the 200-inch Hale telescope. We derive spatially resolved kinematics from the IFS data and use these to study the interaction between the two galaxies. We find the edge-to-edge expansion velocity of the ring is 225 +/- 8 km/s, implying an upper limit on the timescale for the collision of 50 Myrs. We also calculate that the angle of impact for the collision is between 33 degrees-54 degrees, where 0 degrees would imply a perpendicular collision. The ring galaxy is strongly star-forming with the star formation likely to have been triggered by the collision between the two galaxies. We measure some key physical parameters in an integrated and spatially resolved manner for the ring galaxy. Using observed B-I colours and the H-alpha equivalent widths, we conclude that two stellar components (a young and an old population) are required to simultaneously match both observed quantities. We constrain the age range, light and mass fractions of the young star formation in the ring, finding a modest age range, a light fraction of less than a third, and a negligible (<1%) mass fraction. We postulate that the redder colours observed in the SE corner of the ring galaxy could correspond to the nuclear bulge of the original disk galaxy from which the ring was created, consistent with the stellar mass in the SE quadrant being 30-50% of the total. The ring appears to have been a typical disk galaxy prior to the encounter. The ring shows electron densities consistent with typical values for star-forming HII regions. The eastern half of the ring exhibits a metallicity a factor of ~2 higher than the western half. The ionisation parameter, measured across the ring, roughly follows the previously observed trend with metallicity.
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