软X射线背景显示出朝向银河系内部区域的普遍增强。但是这种增强是否是局部特征（例如，距离小于等于200秒差距的超级气泡）和/或与银河系中心/凸起的高能外流有关的现象仍然不清楚。在这里，我们报告了一个比较X射线发射和吸收的研究扩散热气体沿视线向3C 273和Mrk 421，增强和关闭，但在类似的银河系纬度。根据ROSAT全天巡天的估计，3C 273的3/4 keV辐射强度大约是Mrk 421的三倍。基于对这两个活动星系核的\chandra光栅观测，我们探测到了X射线吸收线（例如，OVII K α、K β和OVIII K α在z~0处的跃迁），发现沿这两条视线的平均热气体热力学和运动学性质明显不同。通过减去前景和背景的贡献，确定沿Mrk 421视线，我们隔离的净X射线吸收和发射产生的热气体与增强的方向3C 273。通过对这些差分数据集的联合分析，我们得到温度、分散速度和氢柱密度为2.0（1.6，2.3）E6 K，216（104，480）km/s，2.2（1.4，4.1）E19 cm^{-2}（90%置信区间），假设气体近似等温，太阳在金属丰度，碰撞电离平衡。我们还限制气体的有效视线范围为3.4（1.0，10.1）kpc，强烈表明增强最有可能代表银河系的中心现象。
英文摘要：
The soft X-ray background shows a general enhancement toward the inner region of the Galaxy. But whether this enhancement is a local feature (e.g., a superbubble within a distance of <= 200 pc) and/or a phenomenon related to energetic outflows from the Galactic center/bulge remains unclear. Here we report a comparative X-ray emission and absorption study of diffuse hot gas along the sight lines toward 3C 273 and Mrk 421, on and off the enhancement, but at similar Galactic latitudes. The diffuse 3/4-keV emission intensity, as estimated from the ROSAT All Sky Survey, is about three times higher toward 3C 273 than toward Mrk 421. Based on archival \chandra grating observations of these two AGNs, we detect X-ray absorption lines (e.g., OVII Kalpha, Kbeta, and OVIII Kalpha transitions at z~0) and find that the mean hot gas thermal and kinematic properties along the two sight lines are significantly different. By subtracting the foreground and background contribution, as determined along the Mrk 421 sight line, we isolate the net X-ray absorption and emission produced by the hot gas associated with the enhancement in the direction of 3C 273. From a joint analysis of these differential data sets, we obtain the temperature, dispersion velocity, and hydrogen column density as 2.0(1.6, 2.3)E6 K, 216(104,480) km/s, and 2.2(1.4, 4.1)E19 cm^{-2}, respectively (90% confidence intervals), assuming that the gas is approximately isothermal, solar in metal abundances, and equilibrium in collisional ionization. We also constrain the effective line-of-sight extent of the gas to be 3.4(1.0, 10.1) kpc, strongly suggesting that the enhancement most likely represents a Galactic central phenomenon.
On the enhanced cosmic-ray ionization rate in the diffuse cloud towards Zeta Persei
宇宙线通量的空间分布对于理解银河系的星际介质具有重要意义。这种分布可以通过沿着不同的视线研究不同的分子种类来分析，这些分子种类的丰度对宇宙射线电离率很敏感。最近，几个研究小组报告说，与标准值zeta（平均值）= 2.5 e-17 s^-1相比，弥散云中的宇宙射线电离率有所增强，这是在致密分子云中测量的。在早期的工作中，我们报告了宇宙射线率的增强20对HD 185418。McCall等人根据观测到的H $_{3}^+ while Le Petit et al. found a cosmic ray enhancement of ~10 to be consistent with their models for this same sight line. Here we revisit zeta Persei and perform a detailed calculation using a self-consistent treatment of the hydrogen chemistry, grain physics, energy and ionization balance, and excitation physics. We show that the value of zeta deduced from the H$ _{3}^+$的丰度，报告了48对英仙座ζ的增强…
Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
H3+的红外吸收线，包括亚稳态R（3，3）l线，已被观测到朝向八个明亮的红外源与热的和大质量的恒星位于银河系中心星团和五重星系团之间的30 pc以东。高速色散的吸收线出现在银河系的中央分子区（CMZ）以及前景的旋臂中。根据H3+谱线的相对强度，CMZ中气体的温度和密度分别为T=200- 300 K和n=50- 200 cm ^-3。所有八颗恒星都检测到高密度的H3+柱，这意味着这种温暖而弥漫的气体环境在CMZ中广泛存在。这些视线的电离率和路径长度的乘积分别比银河系盘中的稠密云和弥散云高1000倍和10倍，这表明电离率zeta不小于10^-15 s^-1，并且L至少在50秒差距的数量级。除了三种先前已知的气体环境之外，温暖和扩散的气体是CMZ的重要组成部分：（1）通过CO和其他分子的无线电发射观测到的冷分子云，（2）热分子云（T=10^4-10^6K）和高度电离的扩散气体（n_e=10- 100 cm ^-3）见于射电复合线、远红外原子线和无线电波散射;（3）超热（T=10^7-10^8K）X射线发射等离子体。它的流行极大地改变了对CMZ环境的理解。GC IRS 3的视线是独一无二的，它显示了额外的H3+吸收成分，这被解释为与环核盘相关的云或射电观测中已知的“50 km s^-1云”。红外泵浦方案作为一种机制，以检查填充（3，3）亚稳能级在这个云。
