MAPPING THE POLARIZATION OF THE RADIO-LOUD Lyα NEBULA B3 J2330+3927
MAPPING THE POLARIZATION OF THE RADIO-LOUD Lyα NEBULA B3 J2330+3927
复制标题
绘制射电大声 Lyα 星云 B3 J2330+3927 的偏振图
DOI：
10.3847/1538-4357/834/2/182
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
M. Lee
中科院分区：
文献类型：
--
作者：
Chang You;A. Zabludoff;Paul S. Smith;Yujin Yang;Eunchong Kim;B. Jannuzi;M. Prescott;Y. Matsuda;M. Lee
Lyα星云或“Lyα斑点”是由Lyα发射气体构成的延伸（最高可达100 kpc）、明亮（LLyα = 1043 erg s−1）的云，它们往往位于z = 2-5的过密区域。Lyα发射的起源仍然未知，但最近的理论工作表明，测量偏振可能会区分供电机制。在这里，我们提出了第一个窄带成像偏振测量的射电大声Lyα星云，B3 J2330+3927，在z = 3.09，嵌入活动星系核（AGN）。活动星系核位于团块的Lyα发射峰附近，其射电瓣大致与团块的主轴对齐。利用6.5 m MMT望远镜上的SPOL偏振计，我们在半径为0.″6（4.4 kpc）的圆孔网格中绘制了总（Lyα +连续谱）偏振图，在9个孔径中检测到显著的（>2σ）偏振分数P%，在其他地方达到了很强的上限（低至2%）。P%从距团块中心15 kpc处的<2%增加到15 kpc-25 kpc处的17%。探测到的信号是不对称分布的，大致沿着星云的主轴。偏振角θ大部分垂直于该轴。将Lyα通量与连续谱的通量进行比较，并保守地假设连续谱是高度偏振的（20%-100%），并且与总偏振一致，我们将Lyα发射的偏振下限P%，Lyα的范围从距离团块中心105 kpc处的无显著偏振到10-25 kpc处的3%-17%。像总偏振一样，Lyα偏振检测更经常发生在沿着斑点的主轴。
Lyα nebulae, or “Lyα blobs,” are extended (up to ∼100 kpc), bright (LLyα ≳ 1043 erg s−1) clouds of Lyα emitting gas that tend to lie in overdense regions at z ∼ 2–5. The origin of the Lyα emission remains unknown, but recent theoretical work suggests that measuring the polarization might discriminate among powering mechanisms. Here we present the first narrowband imaging polarimetry of a radio-loud Lyα nebula, B3 J2330+3927, at z = 3.09, with an embedded active galactic nucleus (AGN). The AGN lies near the blob’s Lyα emission peak, and its radio lobes align roughly with the blob’s major axis. With the SPOL polarimeter on the 6.5 m MMT telescope, we map the total (Lyα + continuum) polarization in a grid of circular apertures of a radius of 0.″6 (4.4 kpc), detecting a significant (>2σ) polarization fraction P% in nine apertures and achieving strong upper limits (as low as 2%) elsewhere. P% increases from <2% at ∼5 kpc from the blob center to 17% at ∼15–25 kpc. The detections are distributed asymmetrically, roughly along the nebula’s major axis. The polarization angles θ are mostly perpendicular to this axis. Comparing the Lyα flux to that of the continuum and conservatively assuming that the continuum is highly polarized (20%–100%) and aligned with the total polarization, we place lower limits on the polarization of the Lyα emission P%,Lyα ranging from no significant polarization at ∼5 kpc from the blob center to 3%–17% at 10–25 kpc. Like the total polarization, the Lyα polarization detections occur more often along the blob’s major axis.