We present a detailed analysis of the single-slit optical spectrum of the flat-spectrum radio quasar (FSRQ) B2 0003+38A, taken by the Echellette Spectrograph and Imager (ESI) on the Keck II telescope. This classical low-redshift FSRQ (z = 0.22911, as measured from the stellar absorption lines) remains underexplored in its emission lines, though its broadband continuum properties from radio to X-ray are well studied. After removing the unresolved quasar nucleus and the starlight from the host galaxy, we obtain a spatially resolved 2D spectrum, which clearly shows three components, indicating a rotating disk, an extended emission-line region (EELR), and an outflow. The bulk of the EELR, with a characteristic mass M _EELR ∼ 10⁷ M _⊙, and redshifted by v _EELR ≈ 120 km s⁻¹ with respect to the quasar systemic velocity, shows a one-sided structure stretching to a projected distance of r _EELR ∼ 20 kpc from the nucleus. The rotation curve of the rotating disk is consistent with that of a typical galactic disk, suggesting that the FSRQ is hosted by a disk galaxy. This conclusion is in accordance with the facts that strong absorption in the H i 21 cm line was previously observed, and that Na i λ λ5891, 5897 and Ca ii λ λ3934, 3969 doublets are detected in the optical ESI spectrum. B2 0003+38A will become the first FSRQ discovered to be hosted by a gas-rich disk galaxy, if this is confirmed by follow-up deep imaging and/or integral field unit mapping with a high spatial resolution. These observations will also help unravel the origin of the EELR.

我们详细分析了平谱射电类星体 (FSRQ) B2 0003+38A 的单缝光谱，由 Keck II 望远镜上的 Echelllette 光谱仪和成像仪 (ESI) 拍摄。这种经典的低红移 FSRQ（从恒星吸收线测量的z = 0.22911）在其发射线中仍未得到充分探索，尽管其从无线电到 X 射线的宽带连续谱特性得到了很好的研究。从宿主星系中去除未解析的类星体核和星光后，我们获得了空间解析的二维光谱，它清楚地显示了三个分量，表示旋转盘、扩展发射线区域 (EELR) 和外流。EELR 的主体，特征质量M _EELR ∼ 10 ⁷ M _⊙，并且相对于类星体系统速度由v _EELR ≈ 120 km s ^-1红移，显示了一个单侧结构延伸至距核的投影距离r _EELR ∼ 20 kpc。旋转盘的旋转曲线与典型的银盘一致，表明FSRQ由盘状星系托管。这一结论是根据与在H强吸收的事实我21厘米线以前观察到的，和该娜我 λ λ 5891，5897和Ca II λ λ在光学 ESI 光谱中检测到 3934、3969 个双峰。B2 0003+38A 将成为发现的第一个由富含气体的盘状星系托管的 FSRQ，如果这得到后续深度成像和/或具有高空间分辨率的积分场单元映射证实。这些观察结果也将有助于解开 EELR 的起源。