Physalis系统：在一对具有偏移X射线辐射的相互作用大质量早型星系周围发现类ORC射电壳层
The Physalis system: Discovery of ORC-like radio shells around a massive pair of interacting early-type galaxies with offset X-ray emission
AI总结：
本研究借助ASKAP射电观测与XMM-Newton X射线数据，在75 Mpc外的相互作用早型星系对周围发现类奇异射电圈（ORC）的大射电壳层，结合Magneticum项目模拟提出其由中心AGN释能与并合激波共同产生。
摘要：
我们公布了在一对相互作用的大质量星系周围发现大型射电壳层，且壳层内部存在延展弥散X射线辐射的成果。射电数据由澳大利亚平方公里阵列探路者（Australian Square Kilometer Array Pathfinder，ASKAP）在中心频率分别为944 MHz和1.4 GHz的两个频段获取，X射线数据则来自XMM-牛顿（XMM-Newton）天文台。宿主星系对由早型星系ESO 184-G042和LEDA 418116组成，属于距离仅75 Mpc（红移z=0.017）的一个松散星系群。观测到的该系统（命名为ASKAP J1914-5433，即Physalis）的外部射电壳层（直径约145 kpc）与脊状中心辐射，很可能与中心星系ESO 184-G042形成过程中的并合激波相关，且与新一类奇异射电圈（odd radio circles，ORCs）相似。最亮的X射线辐射并非位于Physalis系统中心，而是偏移至质量更小的星系LEDA 418116处，这一发现为上述观点提供了支撑。宿主星系对包裹在不规则的弥散光包层中，表明相互作用仍在持续。我们结合射电与X射线研究，还利用来自Magneticum项目的星系并合周围星系周介质（circumgalactic medium，CGM）高分辨率模拟，分析了Physalis系统的演化状态。我们认为，ORCs/射电壳层可能由中心活动星系核（AGN）的能量释放，加上穿行于这类系统星系周介质中的并合激波激发射电辐射共同产生。
英文摘要：
We present the discovery of large radio shells around a massive pair of interacting galaxies and extended diffuse X-ray emission within the shells. The radio data were obtained with the Australian Square Kilometer Array Pathfinder (ASKAP) in two frequency bands centred at 944 MHz and 1.4 GHz, respectively, while the X-ray data are from the XMM-Newton observatory. The host galaxy pair, which consists of the early-type galaxies ESO 184-G042 and LEDA 418116, is part of a loose group at a distance of only 75 Mpc (redshift z = 0.017). The observed outer radio shells (diameter ~ 145 kpc) and ridge-like central emission of the system, ASKAP J1914-5433 (Physalis), are likely associated with merger shocks during the formation of the central galaxy (ESO 184-G042) and resemble the new class of odd radio circles (ORCs). This is supported by the brightest X-ray emission found offset from the centre of the Physalis system, instead centered at the less massive galaxy, LEDA 418116. The host galaxy pair is embedded in an irregular envelope of diffuse light, highlighting on-going interactions. We complement our combined radio and X-ray study with high-resolution simulations of the circumgalactic medium (CGM) around galaxy mergers from the Magneticum project to analyse the evolutionary state of the Physalis system. We argue that ORCs / radio shells could be produced by a combination of energy release from the central AGN and subsequent lightening up in radio emission by merger shocks traveling through the CGM of these systems.
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