LOFAR MSSS：发现与扰动星系群有关的2.56 Mpc巨型射电星系
LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group
摘要：
我们报道了在LOFAR多频快照巡天（MSSS）中发现的一个巨大的射电星系（GRG），其在天空中的投影大小为$2.56 \pm 0.07$ Mpc。它与星系三联体UGC 9555有关，其中一个在斯隆数字巡天（SDSS）中被确认为宽线星系，红移为$0.05453 \pm 1 \times 10^{-5} $，速度色散为$215.86 \pm 6.34$ km/s。从档案射电观测，我们看到，这个星系主机紧凑的平谱射电源，我们的结论是，它是活动星系核（AGN）负责产生无线电波瓣。喷流的射电光度分布和活动星系核的粗线分类表明，这个GRG的方向远离天空平面，使其物理尺寸成为已知的最大的GRG之一。红外数据的分析表明，主机是一个透镜型星系与大恒星质量（$\log~\mathrm{M}/\mathrm{M}_\odot = 11.56 \pm 0.12$），和中等恒星形成率（$1.2 \pm 0.3~\mathrm{M}_\odot/\mathrm{year}$）。空间平滑的SDSS图像显示，UGC 9555周围的系统受到显著干扰，并向东南方向显著延伸。总的来说，证据表明这个宿主星系最近经历了一次或多次适度的合并事件，并且还经历了与周围星系的潮汐相互作用，这导致了恒星的形成，并提供了气体供应来触发和燃料Mpc尺度的射电瓣。
英文摘要：
We report on the discovery in the LOFAR Multifrequency Snapshot Sky Survey (MSSS) of a giant radio galaxy (GRG) with a projected size of $2.56 \pm 0.07$ Mpc projected on the sky. It is associated with the galaxy triplet UGC 9555, within which one is identified as a broad-line galaxy in the Sloan Digital Sky Survey (SDSS) at a redshift of $0.05453 \pm 1 \times 10^{-5} $, and with a velocity dispersion of $215.86 \pm 6.34$ km/s. From archival radio observations we see that this galaxy hosts a compact flat-spectrum radio source, and we conclude that it is the active galactic nucleus (AGN) responsible for generating the radio lobes. The radio luminosity distribution of the jets, and the broad-line classification of the host AGN, indicate this GRG is orientated well out of the plane of the sky, making its physical size one of the largest known for any GRG. Analysis of the infrared data suggests that the host is a lenticular type galaxy with a large stellar mass ($\log~\mathrm{M}/\mathrm{M}_\odot = 11.56 \pm 0.12$), and a moderate star formation rate ($1.2 \pm 0.3~\mathrm{M}_\odot/\mathrm{year}$). Spatially smoothing the SDSS images shows the system around UGC 9555 to be significantly disturbed, with a prominent extension to the south-east. Overall, the evidence suggests this host galaxy has undergone one or more recent moderate merger events and is also experiencing tidal interactions with surrounding galaxies, which have caused the star formation and provided the supply of gas to trigger and fuel the Mpc-scale radio lobes.
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