与3C 236射电活动再点燃相耦合的幕式恒星形成
Episodic Star Formation Coupled to Reignition of Radio Activity in 3C 236
摘要：
我们提出了哈勃太空望远镜的紫外和光学成像的射电星系3C 236，其遗迹4兆秒差距的射电喷流瓣和内部2千秒差距的CSS射电源的AGN活动的多个时代的证据。我们的数据证实了存在四个明亮的结的FUV发射在一个弧形沿边缘的内部环核尘埃盘在星系的核心，以及FUV发射与核本身的空间。我们将这些解释为最近或正在形成的恒星。我们目前的测光这些结，以及估计的内部消光源使用的Balmer减量SDSS光谱。我们估计的年龄的结比较我们的消光校正测光与恒星星族合成模型。我们发现与尘埃盘共空间的四个结是年轻的，大约10^7年。核中的FUV辐射可能是由于大约10^9年前触发的恒星形成事件。我们认为，年轻的10^7岁的结源于恒星形成的一个插曲，这与导致射电活动重新点燃的事件大致相同，创造了CSS源。核心中年龄为10^9年的恒星可能与上一个时期的活动有关，该时期产生了4 Mpc的残余源，然后被耗尽或中断所切断。考虑到核尘埃的扰动形态和“老”和“年轻”射电源的双-双形态，这些节点的年龄为活动星系核/星暴的连接提供了证据。我们认为活动星系核的燃料供应由于一次小的合并事件而中断了约10^7年，现在已经恢复，由此产生的非定常气体流向核很可能是导致新一幕的坠星诱导恒星形成和多个时期的射电活动的原因。
英文摘要：
We present Hubble Space Telescope UV and optical imaging of the radio galaxy 3C 236, whose relic 4 Mpc radio jet lobes and inner 2 kpc CSS radio source are evidence of multiple epochs of AGN activity. Our data confirm the presence of four bright knots of FUV emission in an arc along the edge of the inner circumnuclear dust disk in the galaxy's nucleus, as well as FUV emission cospatial with the nucleus itself. We interpret these to be sites of recent or ongoing star formation. We present photometry of these knots, as well as an estimate for the internal extinction in the source using the Balmer decrement from SDSS spectroscopy. We estimate the ages of the knots by comparing our extinction-corrected photometry with stellar population synthesis models. We find the four knots cospatial with the dusty disk to be young, of order 10^7 yr old. The FUV emission in the nucleus is likely due to an episode of star formation triggered ~10^9 yr ago. We argue that the young 10^7 yr old knots stem from an episode of star formation that was roughly coeval with the event resulting in reignition of radio activity, creating the CSS source. The 10^9 yr old stars in the nucleus may be associated with the previous epoch of activity that generated the 4 Mpc relic source, before it was cut off by exhaustion or interruption. The ages of the knots, considered in context with the disturbed morphology of the nuclear dust and the double-double morphology of the "old" and "young" radio sources, present evidence for an episodic AGN/starburst connection. We suggest that the AGN fuel supply was interrupted for ~10^7 yr due to a minor merger event and has now been restored, and the resultant non-steady flow of gas toward the nucleus is likely responsible for both the new episode of infall-induced star formation and also the multiple epochs of radio activity.
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