发表机构
Dartmouth College; Space Telescope Science Institute; Technical University of Denmark; University of Copenhagen; Queen’s University; University of Surrey; Caltech; University of Tampa; AURA/Rubin Observatory（达特茅斯学院; 太空望远镜科学研究所; 丹麦技术大学; 哥本哈根大学; 女王大学; 萨里大学; 加州理工学院; 坦帕大学; 美国天体物理学联合大学/鲁宾天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究在LMC质量星系NGC 55的晕中发现一条恒星流，通过动力学模型推断其可能源于并合或卫星瓦解，表明孤立矮星系也有复杂吸积历史。
AI 中文摘要
我们报告了在LMC质量矮星系NGC 55（距离2 Mpc）的晕中探测到一条此前未被发现的恒星流，这是正在进行的DECam本地体积探索（DELVE）巡天DEEP部分中表征LMC/SMC质量矮星系恒星晕工作的一部分。该结构与Hα发射示踪的外流、中性氢的支流和云团，以及超弥散且可能正在瓦解的卫星星系NGC 55-dw1对齐。我们通过局域光度-金属丰度关系和一组包含气体、恒星及暗物质成分的玩具动力学模型，研究该星流可能的系外前身星情景。如果该星流是先前并合的产物，根据探测到的恒星族的推断，其前身星系绝对星等$M_V \leq -7.2$，恒星质量$M_* \geq 10^5 M_{\odot}$。如果它是来自超弥散卫星的瓦解物质，则它们共同的前身星系绝对星等$M_V \leq -8.3$，恒星质量$M_* \geq 10^{5.2} M_{\odot}$。我们将我们的星流和前身星情景与NGC 300（一个恒星质量与NGC 55相似且已知其晕中存在多个结构的星系）进行比较。我们的结果表明，即使是相对孤立的LMC质量星系也可能具有复杂的吸积历史，为低质量下的层级星系形成提供了新的检验。
英文摘要
We present a previously undetected stellar stream in the halo of the LMC-mass dwarf galaxy NGC 55 (2 Mpc), as part of an ongoing effort to characterize the stellar halos of LMC/SMC-mass dwarfs in the DEEP component of the DECam Local Volume Exploration (DELVE) survey. This structure is aligned with an outflow traced by H$α$ emission, a spur and cloud of neutral hydrogen, and the ultra-diffuse and possibly disrupting satellite galaxy NGC 55-dw1. We investigate possible ex-situ progenitor scenarios for this stream through the local luminosity-metallicity relation and a set of toy dynamical models that include gaseous, stellar, and dark matter components. If the stream is a product of a previous merger, the progenitor galaxy had an absolute magnitude $M_V \leq -7.2$ and a stellar mass $M_* \geq 10^5 M_{\odot}$ based on extrapolations of the detected stellar populations. If it is disrupted material from the ultra-diffuse satellite, their shared progenitor had an absolute magnitude $M_V \leq -8.3$ and a stellar mass $M_* \geq 10^{5.2} M_{\odot}$. We compare our stream and progenitor scenarios to those for NGC 300, a galaxy with a stellar mass similar to that of NGC~55 and known to host multiple structures in its halo. Our results demonstrate that even relatively isolated LMC-mass galaxies can have complex accretion histories, providing new tests of hierarchical galaxy formation at low masses.
Comments21 pages, 9 figures, submitted to ApJ
