We present the discovery of a vast cloud of ionized gas 13$^{\prime}$ (32 kpc) north of the interacting system M51. We detected this cloud via deep narrow-band imaging with the Burrell Schmidt Telescope, where it appears as an extended, diffuse H$α$-emitting feature with no embedded compact regions. The Cloud spans $\sim$10$^{\prime}\times$3$^{\prime}$ (25$\times$7.5 kpc) in size and has no stellar counterpart; comparisons with our previous deep broadband imaging show no detected continuum light to a limit of $μ_{\rm lim, B} \sim$30 mag arcsec$^{-2}$. WIYN SparsePak observations confirm the cloud's kinematic association with M51, and the high NII/H$α$, SII/H$α$, and OI/H$α$ line ratios we measure imply a hard ionization source such as AGN photoionization or shock heating rather than photoionization due to young stars. Given the strong NII emission, we infer roughly solar metallicity for the cloud, ruling out an origin due to infall of primordial gas. Instead we favor models where the gas has been expelled from the inner regions of the M51 system due to tidal stripping or starburst/AGN winds and has been subsequently ionized either by shocks or a fading AGN. This latter scenario raises the intriguing possibility that M51 may be the nearest example of an AGN fossil nebula or light echo, akin to the famous "Hanny's Voorwerp" in the IC 2497 system.
JWST Discovery of High-Velocity Mid-Infrared Ionized Outflows in Ultraluminous Infrared Galaxies F11119+3257 and F05189-2524
University of Maryland（马里兰大学）；Rhodes College（罗兹学院）；Universidad de Alcalá（阿尔卡拉大学）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心（CAB），西班牙国家航空航天技术研究所/西班牙高等科学研究委员会）；University of Arizona（亚利桑那大学）；Max Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）；Space Telescope Science Institute（太空望远镜科学研究所）；Instituto de Física Fundamental (IFF), CSIC（基础物理研究所（IFF），西班牙高等科学研究委员会）
Discovery of a strong ionized-gas outflow in an AKARI-selected Ultra-luminous Infrared Galaxy at z = 0.5
为了构造一个0.5 < z < 1的超亮红外星系（ULIRGs，具有红外光度，$L_{\rm IR} > 10^{12}$ L $_{\odot}$）的样本，我们正在进行一个光学跟踪计划，以获得明亮的90- $μ$ m远红外源，并在AKARI远红外巡天（FIS）亮源目录（Ver.2）中选择一个暗淡的光学（i < 20）对应源。AKARI-FIS-V2 J 0916248 +073034在光谱跟踪观测中被识别为z = 0.49的ULIRG，表明其发射线轮廓中存在极强外流的特征。它的[OIII] 5007发射线相对于恒星吸收线的半高宽为1830 km s $^{-1}$，速度漂移为-770 km s $^{-1}$。此外，低电离态[OII] 3726 3729双谱线还显示出910 km s $^{-1}$的大半高宽和-380 km s $^{-1}$的速度漂移。在去除未分辨的核成分后，长缝光谱2D图像可能显示流出物延伸到4kpc的半径。质量外流和能量喷射率分别为500 M $_{\odot}$ yr $^{-1}$和$4\times10^{44}$ erg s $^{-1}$，这意味着在0.3 < z < 1.6时，外流是ULIRGs和类星体中观测到的最强的外流。强外流和强烈的恒星形成（恒星形成速率为990 M $_{\odot}$ yr $^{-1}$）的共存表明，强外流的反馈对星系…
ALMA CO Observations of Supernova Remnant N63A in the Large Magellanic Cloud: Discovery of Dense Molecular Clouds Embedded within Shock-Ionized and Photoionized Nebulae
XRISM Discovery of Multiple Ionized Fe-K Emission and Absorption Components in Centaurus A
Hiroshima University（广岛大学）；Tsinghua University（清华大学）；The University of Michigan（密歇根大学）；Saint Mary’s University（圣玛丽大学）；National Aeronautics and Space Administration, Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；University of Maryland, Baltimore County (UMBC)（马里兰大学巴尔的摩县分校）；University of Maryland, College Park（马里兰大学帕克分校）；Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）
XRISM 发现 Centaurus A 中多个离子化 Fe-K 发射和吸收成分，揭示环核环境与 AGN 统一模型的关系。
Discovery of the Slowest Radio Pulsar in the Small Magellanic Cloud
Trinity College, Univeristy of Cambridge（剑桥大学三一学院）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（阿尔伯特·爱因斯坦研究所））；Leibniz Universität Hannover（汉诺威莱布尼茨大学）
