HI Gas and Star Formation in Major Galaxy Pairs from the FAST All-Sky HI Survey (FASHI)
Xiamen University（厦门大学）；Università degli Studi di Firenze（佛罗伦萨大学）；International School of Beijing（北京国际学校）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Chinese Academy of Sciences South America Center for Astronomy（中国科学院南美天文中心）；Guizhou Radio Astronomical Observatory, Guizhou University（贵州大学贵州天文观测站）
Shulan Yan, Qingzheng Yu, Taotao Fang, Chuan He, Andrew Ma, Junfeng Wang, C. Kevin Xu, Ming Zhu, Weishan Zhu
Atomic hydrogen (HI) plays a fundamental role in fueling star formation in galaxies. However, the behavior of HI gas in interacting systems, particularly galaxy pairs, remains elusive. In this work, we investigate the HI content of major mergers by cross-matching the extragalactic HI catalog from the FAST All-Sky HI Survey (FASHI) with a previously established sample of isolated galaxy pairs. With the superior sensitivity of FAST, we have constructed the largest sample of major mergers with HI detections, consisting of $440$ galaxy pairs: $364$ spiral-spiral (S+S) and $76$ spiral-elliptical (S+E) systems. We examine the HI gas fraction ($f_{\mathrm{HI}}$), star formation rate (SFR) and HI star formation efficiency ($\mathrm{SFE_{HI}}=\mathrm{SFR}/M_{\rm HI}$) for individual galaxies in pairs. The control sample is matched in both stellar mass and redshift. We find that paired galaxies, particularly those in pairs with small projected separations ($d_{\mathrm{p}}<50\ h^{-1}\mathrm{kpc}$), exhibit systematically lower (by $8.8\%$) HI gas fractions compared to the control galaxies. The SFR is enhanced for galaxies in S+S pairs. $\mathrm{SFE_{HI}}$ is $\sim15\%$ higher for galaxies in S+S pairs than in the control galaxies, while spiral galaxies in S+E pairs show no significant difference in $\mathrm{SFE_{HI}}$ compared to the control sample. These findings suggest that the merging process triggers efficient HI gas depletion and enhances star formation, especially in close S+S pairs. Notably, our sample includes $26$ red spirals in paired systems. These galaxies exhibit HI deficiency and suppressed star formation activity compared to the isolated galaxies, indicating that interactions may affect quiescent spirals differently, potentially due to mechanisms similar to ellipticals.
The FAST All Sky HI Survey DR2: the FASHI Catalog and the HI Mass Function
State Key Laboratory of Radio Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台射电天文与技术重点实验室）；Guizhou University（贵州大学）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS（中国科学院国家天文台中国-南美天文中心）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）
Optical identification of the FASHI sources: toward the extended Local Volume
Special Astrophysical Observatory, Russian Academy of Sciences（俄罗斯科学院特别天文台）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Guizhou Radio Astronomical Observatory, Guizhou University（贵州大学贵州天文 radio 观测站）
Winged Radio Sources from LOFAR Two-metre Sky Survey First Data Release (LoTSS DR1)
有翼射电源是河外射电源的一个小子类，它显示出一对低表面亮度的射电源瓣，被称为“翅膀”，与主喷流成一定角度。根据机翼的位置，这些星系看起来像X或Z，被称为X形射电星系（XRG）或Z形射电星系（ZRG）。我们报告了从LOFAR两米巡天第一次数据发布（LoTSS DR 1）中识别出的33个有翼射电源，其中21个源被确定为X形射电星系和12个Z形射电星系。为14个XRG（67%）和12个ZRG（100%）确定了光学对应物。我们研究了这些源的各种物理参数，如光谱指数，射电光度和功率。大多数XRG和ZRG的射电频谱是陡峭的（$α_{1400}^{144}>0.5$），这是典型的瓣控射电星系。对X射线衍射图的长短轴相对大小和长短轴夹角进行了统计学研究。
The SkyMapper-Gaia RVS view of the Gaia-Enceladus-Sausage -- an investigation of the metallicity and mass of the Milky Way's last major merger
我们的特点盖亚-土卫二香肠运动学结构最近发现的银河系晕使用光度金属丰度从SkyMapper调查，和盖亚径向速度测量的运动学。通过检查的金属丰度分布函数（MDF）的恒星在运动学/动作空间中，我们发现，$\sqrt{J_R}$与$L_z$空间允许最干净的选择盖亚-土卫二-香肠星与最小的污染，从盘或晕星形成的原位或在其他过去的合并。具有$30 \leq \sqrt{J_R} \leq 50$（kpc km s $^{-1})^{1/2}$和$-500 \leq L_z \leq 500$ kpc km s $^{-1}$）的恒星具有以[Fe/H] $= -1.17$ dex为中心的窄色散，色散为0.34 dex。该[Fe/H]估计值比文献估计值（通过$0.1-0.3$ dex）更富含金属。基于MDFs，我们发现，选择盖亚-土卫二-香肠星在其他运动/行动空间没有额外的人口信息导致污染的样本。根据我们的标准选择的干净的盖亚-土卫二-香肠样品略微逆行，位于高$V_T$晕CMD双序列的蓝色序列。使用来自宇宙学模拟的星系质量-金属丰度关系，并假设平均恒星年龄为10 Gyr，我们估计盖亚-土卫二-香肠祖卫星的质量为$10^{8.85-9.85}$ M $_{\odot}$，这与基于光盘动态和模拟的文献估计一致。为了更复杂地选择纯粹的盖亚-土卫二-香肠星，还需要更多关于详细丰度和年龄的信息。
FASHI DR2: A Catalog of 132 Low-Redshift HI 21 cm Absorption Systems
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Guizhou University（贵州大学）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Shanghai Jiao Tong University（上海交通大学）；Chinese Academy of Sciences South America Center for Astronomy（中国科学院南美天文中心）
HI-detected Dwarf Galaxies in the FASHI Survey: Insights from Single- and Double-Peaked Emission-Line Samples
Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS（中国科学院南美天文中心，国家天文台）；Key Laboratory of Optical Astronomy, NAOC（光学天文重点实验室，国家天文台）；Harvard-Smithsonian Center for Astrophysics（哈佛-史密森天体物理中心）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Department of Astronomy, University of Science and Technology of China（中国科学技术大学天文系）；School of Astronomy and Space Sciences, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；Guizhou Radio Astronomical Observatory, Guizhou University（贵州大学贵州无线电天文观测台）
A Sample of 459 Galaxy Groups Identified from the FAST All Sky HI Survey DR2
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences（中国科学院FAST国家重点实验室，国家天文台，中国科学院）；School of Astronomy, University of Chinese Academy of Sciences（中国科学院大学天文学系）
