发表机构
Arizona State University; Università di Firenze; INAF - Osservatorio Astrofisico di Arcetri; Inter-University Centre for Astronomy and Astrophysics; University of California, San Diego; Eureka Scientific Inc.; National Radio Astronomy Observatory（亚利桑那州立大学; 佛罗伦萨大学; 意大利国家天体物理研究所阿切特里天文台; 大学间天文与天体物理中心; 加州大学圣地亚哥分校; 尤里卡科学公司; 美国国家射电天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过甚大阵列和MMT观测，发现NGC 3344的XUV盘中径向气体内流（平均速度6 km/s）稀释金属丰度，产生异常低金属丰度区域，并首次直接证实径向气体流动驱动恒星盘扩张和由内而外的星系增长。
AI 中文摘要
我们展示了将异常低金属丰度区域与星系NGC 3344的扩展紫外（XUV）盘中的径向气体内流联系起来的证据。异常低金属丰度的H II区域被假设为是由贫金属气体的吸积引起的，但气体流动与低金属丰度气体之间的直接联系此前尚未被确立。我们使用甚大阵列的高分辨率H I-21厘米成像来追踪中性气体运动学，并使用MMT的多狭缝光学光谱来追踪NGC 3344中76个H II区域的气相金属丰度。该星系呈现出负的径向金属丰度梯度，为$-0.378$ dex $\mathrm{R}_{25}^{-1}$，其中XUV盘中的H II区域显示出比内盘区域近两倍的金属丰度离散度，且若干区域显示出异常低的金属丰度。使用3DBarolo将H I盘建模为倾斜环，我们发现气体在XUV盘内以平均径向速度6 $\mathrm{km\\, s^{-1}}$向内运动，这可能为恒星形成提供燃料并稀释金属丰度，从而产生异常低金属丰度区域。化学演化模型表明，气体分数、有效产量和质量载荷因子剖面在XUV盘起始处被打乱，这与近期气体流动的预期一致。这一例子是首次直接探测到径向气体流动如何支持恒星盘扩张并导致由内而外的星系增长。
英文摘要
We present evidence connecting anomalously low-metallicity regions to radial gas inflows in the extended ultraviolet (XUV) disk of the galaxy NGC 3344. Anomalously low-metallicity H II regions are hypothesized to result from the accretion of metal-poor gas, but a direct link between gas flows and low metallicity gas has not been previously established. We use high-resolution H I-21cm imaging from the Very Large Array to trace neutral gas kinematics and multi-slit optical spectroscopy from the MMT to trace the gas-phase metallicity of 76 H II regions in NGC 3344. The galaxy exhibits a negative radial metallicity gradient of $-0.378$ dex $\mathrm{R}_{25}^{-1}$, with H II regions in the XUV disk showing nearly twice the metallicity scatter of those in the inner disk and several showing an anomalously low metallicity. Modeling the H I disk as tilted rings with 3DBarolo, we find gas moving radially inwards within the XUV disk at an average radial velocity of 6 $\mathrm{km\ s^{-1}}$, likely fueling star formation and diluting the metallicity, thereby producing anomalously low metallicity regions. Chemical evolution models indicate that the gas fraction, effective yield, and mass-loading factor profiles are disrupted at the onset of the XUV disk, as expected from recent gas flows. This example is the first direct detection of how radial gas flows can support stellar disk expansion and cause inside-out galaxy growth.
Comments15 pages, 6 figures, 1 table. Accepted for publication in ApJ
