论文标题
在NGC 891和NGC 4565的环境介质中检测弥漫性HI发射
Detection of the diffuse HI emission in the Circumgalactic Medium of NGC 891 and NGC 4565
论文作者
论文摘要
我们使用Robert C. Byrd C. Byrd Green Bank望远镜（GBT），我们介绍了局部边缘星系NGC 891和NGC 4565中的中性氢（HI）的21厘米发射（HI）。我们的5 $σ$灵敏度为$ 8.2 \ times 10^{16} $ cm $^{ - 2} $在20 km s $^{ - 1} $ CHANNEL上计算出来，我们实现了$>5σ$检测到$ 90-120 $ kpc沿次要轴线。 CGM排放的速度宽度与磁盘$ \ \ 500 $ km s $^{ - 1} $的速度宽度一样大，表明存在弥散的组件渗透到光环中。我们将GBT测量结果与Westerbork合成射电望远镜（WSRT）的干涉数据进行比较。 WSRT在高S/N处映射来自磁盘的HI发射，但在用GBT探测的角度尺度下的表面亮度灵敏度有限。在将WSRT数据卷入GBT的空间分辨率（FWHM = 9.1 $'$）之后，我们发现WSRT检测到的排放量为$ 48^{+15} _ { - 25} _ { - 25} $％（$ 58^{+4} _ {+4} _ {-18} $ ng的cg gm的cg gm的gm 891（NGC 4565）。仅大GBT的通量的存在表明存在大量弥漫性，低柱密度HI在CGM中的发射。为了合理的假设，扩展的散射HI可以占$ 5.2 \ pm0.9 $％和$ 2.0 \ pm0.8 $％的NGC 891和NGC 4565的总HI排放。
We present detections of 21-cm emission from neutral hydrogen (HI) in the circumgalactic medium (CGM) of the local edge-on galaxies NGC 891 and NGC 4565 using the Robert C. Byrd Green Bank Telescope (GBT). With our 5$σ$ sensitivity of $8.2 \times 10^{16}$ cm$^{-2}$ calculated over a 20 km s$^{-1}$ channel, we achieve $>5σ$ detections out to $90-120$ kpc along the minor axes. The velocity width of the CGM emission is as large as that of the disk $\approx 500$ km s$^{-1}$, indicating the existence of a diffuse component permeating the halo. We compare our GBT measurements with interferometric data from the Westerbork Synthesis Radio Telescope (WSRT). The WSRT maps the HI emission from the disk at high S/N but has limited surface brightness sensitivity at the angular scales probed with the GBT. After convolving the WSRT data to the spatial resolution of the GBT (FWHM = 9.1$'$), we find that the emission detected by the WSRT accounts for $48^{+15}_{-25}$% ($58^{+4}_{-18}$%) of the total flux recovered by the GBT from the CGM of NGC 891(NGC 4565). The existence of significant GBT-only flux suggests the presence of a large amount of diffuse, low column density HI emission in the CGM. For reasonable assumptions, the extended diffuse HI could account for $5.2\pm0.9$% and $2.0\pm0.8$% of the total HI emission of NGC 891 and NGC 4565.
