AI 中文总结
本文通过积分场光谱学研究20个2003fg类Ia型超新星宿主星系，发现其偏好低金属丰度、低恒星形成率的宿主外围，支持双白矮星并合起源，或在早期宇宙更常见。
AI 中文摘要
SN~2003fg类事件是Ia型超新星（SN~Ia）的一个特殊子类，其特征为光曲线更宽、近红外光度更高，且早期存在更强的碳吸收。本文呈现了迄今最大规模的2003fg类Ia型超新星宿主星系汇编的观测结果，这些数据通过积分场光谱学（Integral Field Spectroscopy，IFS）获取。我们对20个目标既研究了宿主星系的整体属性，也针对一个规模可观的样本首次研究了超新星位置处的局部环境。整体而言，与正常Ia型超新星相比，2003fg类Ia型超新星发生在恒星质量更低、氧丰度更低、恒星形成率密度（specific star-formation rate，sSFR）略高的星系中；不过它们的宿主星系在这些属性上并不像超亮超新星那样极端，也不代表贫金属矮星系样本。局部来看，与正常Ia型超新星环境相比，2003fg类超新星位置处的恒星形成率、恒星质量面密度和sSFR更低，这与它们显著偏好宿主星系外围的情况一致，而它们的恒星年龄指标是典型的。最显著的局部属性是金属丰度：2003fg类Ia型超新星所处的环境是所有Ia型超新星中金属丰度最低的。我们还发现2003fg类事件的光曲线宽度与氧丰度之间存在初步的正相关。我们的结果表明，2003fg类Ia型超新星源于两颗白矮星（white dwarfs，WDs）的并合或核心简并场景，但不支持单颗快速旋转的超钱德拉塞卡质量碳氧白矮星前身星的通道，因为该通道需要年轻恒星族群，而我们在超新星位置处并未观测到。2003fg类Ia型超新星对低金属丰度环境的偏好意味着它们在早期宇宙中可能更为常见。
英文摘要
SN~2003fg-like events are a peculiar type Ia supernova (SN~Ia) subtype characterized by broader light curves, higher near-infrared luminosities, and stronger carbon absorptions at early times. Here we present observations of the largest compilation of 2003fg-like SN Ia host galaxies to date, obtained with Integral Field Spectroscopy (IFS). For 20 objects, we study both the global host-galaxy properties and, for the first time for a sizeable sample, the local environment at the SN position. Globally, 2003fg-like SNe~Ia occur in galaxies with lower stellar mass, lower oxygen abundance, and marginally higher specific star-formation rate (sSFR) than those of normal SNe~Ia, although their hosts are not as extreme in such properties as superluminous SNe, nor representative of metal-poor dwarf-galaxy samples. Locally, the SN positions show lower star-formation-rate, stellar-mass surface densities, and lower sSFR, than normal SN~Ia environments, consistent with a significant preference for the outskirts of their hosts, while their stellar age indicators are typical. The most distinctive local property is metallicity, with 2003fg-like SNe~Ia occupying the most metal-poor environments among SNe~Ia. We also find a tentative positive correlation between the light-curve width and the oxygen abundance for 2003fg-like events. Our results imply that 2003fg-like SNe~Ia arise from the merger of two white dwarfs (WDs) or the core-degenerate scenario, but disfavor the single, rapidly rotating super-M$_{ch}$ C-O WD progenitor, as this channel requires a young stellar population that we do not observe at the SN positions. The preference of 2003fg-like SNe~Ia for low-metallicity environments suggests that they may have been more common in the early Universe. (abridged)
CommentsAccepted in A&A
